A violet InGaN multi-quantum well/GaN/AlGaN separate- confinement-heterostructure laser diode (LD) was grown on epitaxially laterally overgrown GaN on sapphire. The threshold current density was 2 - 4 kA/cm². The LDs with cleaved mirror facets showed an output power as high as 30 mW under room-temperature continuous-wave (CW) operation. The stable fundamental transverse mode in the near-field patterns was observed at an output power up to 30 mW. The lifetime of the LDs at a constant output power of 5 mW was more than 1,900 hours under CW operation at an ambient temperature of 50 degree(s)C.

An achromatic Fourier system (AFS) performs optically a Fourier transformation in spatially coherent white light, without color blurring. Our design method uses matrix algebra, applied upon the Wigner distribution function. The matrix procedure is similar to what is used in geometrical objects. However, our approach is valid also for wave optics. That is important because the AFS does contain not only refractive lenses, but also diffractive lenses (Fresnel zone plates).

A beam propagating in free space is exposed to the laws of diffraction, which tend to deform the wave front. Hence, 3D beam forming is a very applicable task. For instance it may be useful in designing a special beam to be used for scanning purposes, beam forming for optical communication modules and 3D beam forming as a tool to exceed system's resolving power. There are several techniques, which allow obtaining a reduced sensitivity to diffraction in a pre- determined region of propagation. In this paper a novel optimal technique is suggested. Using the calculus of variation method we derive an analytic expression for an optimal filter in the mean square error sense, to obtain a 3D beam forming, which is as close as possible to the desired 3D distribution. We applied the proposed method for obtaining a scanning beam with improved performances. The suggested approach was tested in computer simulations as well as in optical experiments and was proven to deliver improved performance. Thus one can obtain an extended working region using the resulting beam with confined lateral spread.

Different optical architectures designed for compensating the chromatic dispersion inherent to free-space broadband light diffraction are presented. These devices are formed by a small number of conventional refractive objectives and diffractive lenses. In a second stage, several achromatic diffraction-based information processing techniques working with spatially-coherent or spatially-incoherent white-light illumination are also discussed.

For the first time we show that optical diffraction is a wavelet transform with the electromagnetic wavelets, which are reduced to Hyugens' wavelets by a temporal. Fourier analysis in the case of monochromatic field. We define the non-diffracting electromagnetic wavelet by integrating a subset of the electromagnetic wavelets. A non-diffracting field can be constructed by a linear combination of the non- diffracting electromagnetic wavelets, which are the one-side windowed Fourier transform of the Bessel beams with a temporal frequency window and are spatially localized in the lateral direction, translated in the propagation direction and scaled in the time and the temporal frequency.

We present a phase mask that substantially reduces the influence of focus error of an optical system; while preserving light gathering power, and lateral resolution. Numerical simulations and first experimental results are shown.

The paper describes the decade history and the recent advances in the field of the telescopes, where the nonlinear-optical effects are used for the correction for image distortions, caused by the defects and deformations of the primary mirror and of some other elements. Described are the schemes, based on phase conjugation use, which can work with the coherent radiation (beam direction, laser collimators and imaging with coherent illumination) and the schemes, based on the use of the dynamic holography, applicable to the remote objects (astronomy, Earth observation) in the incoherent radiation with the wide spectrum.

We propose a new concept for an artificial beacon for adaptive optics. A direct extension of the work on sodium is the application of two-photon coherent excitation to create a multiple wavelength beacon.

We have developed a Ti:sapphire/Nd:glass laser system which produces > 1.25 PW peak power. An irradiance of 10²⁰ - 10²¹ W/cm² is achieved utilizing an on-axis parabolic mirror, with adaptive optic wavefront correction. Experimental results will be described.

A mathematical model of the deployment of multiple laser beacons in astronomical imaging has been created and inverted, with the objectives of approaching the diffraction limit of the telescope and widening its field of view. Initial results have proved encouraging, at least within the confines of the assumptions made.

Significant advances have been made in the development and performance of large scale adaptive optical systems in recent years. Technological innovations in sensors, processors, wave front correctors, and laser guide stars have all contributed to the rapid growth of adaptive optics as an enabling technology for ground based optical astronomy in the 21st century.

Capacity growth in networks requires optical crossconnect switches that can be assembled incrementally, probably to large ultimate sizes, preferably using identical submodules of small size. Continued strict-sense nonblocking operation must be ensured during expansion, and expandability should have minimal impact on the initial cost. Large ultimate sizes mandate multistage architectures which impose difficulties in the expansion. We discuss the design of optical switching matrices for > 100 X 100 ports using a new modular multistage architecture that focusses on expandability.

We describe a method by which a lightweight, low-quality, reflecting primary is holographically corrected to diffraction limited operation. The resulting telescope can be used to transmit or receive optical data signals with frequencies up to 100 GHz with high SNR (> 60 dB). The simplicity of this design makes it ideal for future global satellite networks or space probe communications.

Ring networks are the architecture of choice for WDM (Wavelength Division Multiplexing) telecommunication networks because of their inherent survivability, scalability, and large capacity. We describe a novel and efficient algorithm that allows a substantial reduction of the number of wavelengths required for full interconnection of bidirectional WDM ring, yet has much simpler wavelength assignment than the precisely optimal algorithm.

The widespread introduction of erbium-doped fiber amplifiers in lightwave transmission systems has ushered in the WDM (wavelength-division multiplexing) era. Early WDM systems (five years ago) transmitted eight 2.5 Gb/schannels spaced by 200 GHz. In the coming year lightwave systems with 160 channels each at 10 Gb/s spaced by only 50 GHz will be introduced. Such high-capacity systems are plagued by optical nonlinearities in the transmission fibers. Silica fibers exhibit a wide variety of optical nonlinearities that can be grouped into two categories, stimulated scattering and nonlinear refractive index effects. Stimulated scattering processes, such as Brillouin and Raman, cause wavelength conversion of signals, unwanted noise, crosstalk, and power depletion. The nonlinear refractive index of silica is the source of such effects as self-phase modulation (SPM), cross-phase modulation (CPM) and four-photon mixing (FPM). 5PM and CPM produce spectral broadening, pulse distortion, and timing jitter. FPM generates mixing products that can coherently interfere with the signals. An arsenal of techniques has been developed to mitigate the effects of these nonlinearities and this has led to the staggering increase in fiber transmission capacity. This talk will provide an overview of optical nonlinearities in fibers and some of the techniques designed to circumvent them

In this paper, we address some of the most difficult problems encountered in surface scattering. The first part is devoted to our recent work about the rigorous solution for 2D metallic surfaces. An impedance approximation has been implemented to take into account the finite conductivity of the metals, and, to deal with surfaces of arbitrary size, the beam simulation method has been generalized. But still, several problems cannot be rigorously solved in three dimensions. One of them concerns shallow metallic surfaces in optics: how taking accurately into account the propagation of surface polaritons? A second challenge consists in solving a surface scattering problem under grazing incidence. Since the field on the surface spreads out in both problems, the same answer holds. The surface current is described in the Fourier space, while the sampling of the rigorous integral equation is still achieved in the coordinate space. The number of unknowns is drastically reduced, and standard forward solvers can be used. The last problem studied here is a step towards the inverse problem. What kind of geometrical parameter describing the surface can be extracted from intensity measurements in the far field? For multi-scale rough surfaces, we show that the wavelet correlation dimension is a good candidate for such a characterization.

The hybrid filtered backpropagation algorithm of diffraction tomography is known to give good reconstructions of 2D objects with a low contrast relative to the background medium. Here we show how the method can be extended (1) to reconstruct objects with rather large contrasts, and (2) to reconstruct 3D objects.

The Fourier transform is one of the most important concepts in optical signal processing, and in the mathematical theory of signals and systems. It can be implemented optically as well as digitally, and constitutes the building block of more complex information processing operations. The fractional Fourier transform is a generalization of the ordinary Fourier transform and also has efficient digital and optical implementations. However, the fractional order parameter associated with the fractional Fourier transform makes it more versatile than the ordinary Fourier transform, leading to many applications in optics and signal processing.

We present computer simulations of the 2D Fractional Hilbert Transform, of index P for both amplitude and phase objects. We also present, computer simulations of the isotropic version of the classical Hilbert Transform.

The optical implementation of the Radon-Wigner display for 1D objects is used in two different applications. First, it is used in the study of some properties of the wave field diffracted by unidimensional fractal gratings in the Fresnel region. Second, this optical representation is profited to perform a parallel space-variant optical correlation. Computer simulations and experimental results are presented.

Non-stationarity of atmospheric turbulence gives rise to some practical problems when one wants to determine the probability density function (PDF) of intensity fluctuations from laser atmospheric propagation experimental data. For strong fluctuations, the number of uncorrelated data that can be collected in stationary conditions is generally not enough to correctly evaluate intensity moments of order greater than two 1} . In the case of very strong fluctuations even the second order moment (and also variance) can not be estimated with accuracy [2] This is due to the fact that the stronger the fluctuations the longer is the tail of the distribution, which represents the main contribution in high order moment evaluation. If only integer moments are considered, information about intensity PDF that can be extracted from its moments is thus very poor because only a few of them are correctly estimated

We have observed experimental evidence of the effects of non-Kolmogorov turbulence (NKT) on wavefront tilt. In addition, we have observed the anisotropy of the horizontal and vertical tilt components caused by the anisotropy of turbulence near the telescope. We developed an experimental method, which allowed us to eliminate telescope vibration and isolate the atmospheric tilt from the star Polaris. The spatial and temporal statistics of the wavefront tilt were determined by using aperture masks having diameters in the range from 0.1 m up to 3.5 m. The measured dependencies of the tilt variance on the aperture diameter deviate from the prediction based on the Kolmogorov model. These dependencies have a knee, where the tilt variance approaches a constant level determined by NKT. Anisotropy was observed when comparing the X and Y components of wavefront tilt. On average the horizontal outer scale of turbulence estimated from the tilt statistics is larger than the vertical one by a factor of 2-3. Local topographical features and the telescope dome affect the outer scale with the result that the outer scale measured at the 1 .5 m telescope is smaller than that at the 3 .5 m telescope. The tilt power spectra have a ç2/3 andf"3 behavior in the intermediate and high frequency range, respectively, which is predicted by the Kolmogorov model. In the low frequency range, the spectra do not obey the prediction of existing theoretical models. In this range the power spectra of the horizontal tilt exceed that for vertical tilt as a consequence of anisotropy of turbulence. The tilt temporal correlation scale increases with increasing aperture size. For the large apertures the tilt correlation scale is ofthe order of a few seconds.

Volume-Phase Holographic (VPH) gratings provide unique capabilities over classical surface gratings which can be exploited in modern astronomical spectrographs. The peak diffraction efficiency of a VPH grating is tunable due to the nature of Bragg diffraction. This allows a single dispersing element to serve the function of several classical gratings. Additionally, VPH grating structures can be stacked to produce complex gratings capable of directing the diffracted light in ways that classical gratings can not.

The AMM is a new kind of micromachined deformable mirror. It is a silicon mirror which can be electrostatically actuated by electrodes located on each side of the mirror. In this article we describe the characteristics and the results of modelization and testing of our deformable micro mirror.

Adaptive Optical (AO) technology can compensate wave-front error by real-time sensing, controlling, and correcting to improve image and beam quality. The research and development on AO in China began in 1979. In 1980, the first laboratory on AO in China was established in the institute of Optics and Electronics (IOE), Chinese Academy of Sciences (CAS). The main activities of developing AO systems are conducted in this Institute with collaboration of other institutions. Since then several AO systems have been built in this Laboratory. Table I summarized the characteristics of these systems.

Fibers and planar waveguides made from dielectric materials which are periodically patterned on the scale of the optical wavelength--photonic crystals--have quite remarkable properties, requiring a complete realignment of the goal- posts in conventional guided-wave photonics. For example, photonic crystal fibers can be designed to be single-mode at every frequency, and full 2D photonic bandgaps can permit light to be guided--single mode--in a core region where the refractive index is lower than the cladding. A whole menagerie of new possibilities are presently emerging, including hollow-core single-mode optical fibers and ultra- compact micro-components formed in planar photonic crystal films.

A transparent conductor has been developed based on 1D metal/dielectric photonic band gap structures. Laminated metal/dielectric filters containing 100 nm of silver have been fabricated with > 50% transmittance. Applications for transparent, conducting films include antennas embedded in windshields, electrodes on flat panel displays, electromagnetic shielding, and solar window panes.

A novel analysis of specially designed photonic crystal fibers accounts for the existence of endlessly single-mode structures with flattened dispersion. Our approach permits to control the fiber dispersion in terms of its geometrical parameters.

Interest in nonlinear organic materials has been wide because these materials have large optical nonlinearities and quick response times. Polymeric materials are among the most promising organic materials for use in electrooptical applications. We discuss here the advantages of these materials and development of spatial light modulators (SLMs) using them.

Phase-matching conditions for parametric interaction in 1D photonic band gap (PBG) structures are studied. Band edge effects, such as field localization, increased density of modes, and `effective' phase matching between pump and signal fields are responsible for the high predicted enhancement of nonlinear processes in PBGs.

We report on a general analytical procedure to analyze the axial focusing properties of uniform cylindrical waves truncated by a rectangular window. The resulting on axis diffraction pattern explicitly depends on the square of the window height-to-width ratio. Depending on the value of this parameter, different kinds of axial behavior are observed. In particular, it is found that for low values of this parameter and low Fresnel number, an inverse focal-shift phenomenon can appear.

The objective of this paper is to show different aspects of the interaction of light with wavelength sized optical microstructures, and their imaging. Furthermore, we outline that a microoptical structure can generate a laminar or a turbulent optical field.

Non-diffracting beams represent a group of fields whose radial intensity distributions do not change during their propagation. In 1987 Durnin" showed that the field described by E(r, z, t) = A . Jo(k1r) . ei11t) (1) is an exact solution of the wave equation, where k + k = w2/c2, and J0 is the zero order Bessel function of the first kind. The field described by Eq. (1) represents a non-diffracting beam because the transverse intensity distribution is independent of the propagation distance (z). However, such an ideal beam cannot be realized experimentally over large values of z and r, since this would represent a beam with infinite energy and spatial extent. In the last twelve years several experimental arrangements have been proposed21 to create nearly non-diffracting Bessel beams and apply them in different domains of physics. In 1997 a new approach was suggested by the authors [3,4J for enhancing both the critical dimension (CD) and depth of focus (DOF) in optical microlithography based on Bessel beams. A Fabry-Perot etalon placed between the mask and the projection lens creates multiple images of the original mask pattern along the optical axis. The distance and the exact phase between these virtual images can be controlled by the separation of the etalon mirrors. The projection lens produces perfect images of the virtual mask patterns, shifted in position along the optical axis, in contrast with the conventional projection process, which produces a single image at the wafer surface. Preliminary theoretical and experimantal results showed that an etalon with optimized mirror separation is capable of enhancing the CD and DOF by 60% and 400%, respectively, using a single on-axis contact hole. In order to evaluate this technique for more complex, and realistic extended mask patterns, a microlithographic simulation tool must be employed. This software, however, is not configured in such a way that it can be immediately adapted to simulate the Fabry-Perot approach. An elegant and efficient method to model this Fabry-Perot technique is to represent the effect of the etalon with an appropriate pupil-plane filter. Such filters with a complex amplitude-phase transmission can be easily implemented in any simulation tool. In this work Prolith/2, a commercially available simulation software, was used to evaluate the aerial image of contact hole arrays and line-space patterns with different pitch sizes. Figure 1 depicts a typical 2D intensity distribution for an off-set hole array with and without filter. The resolution enhanced by 25%, while the filter shifted the optimum focal position by 5 microns towards the lens. Due to constructive interference between the diffraction rings, secondary maxima appeared between the main peaks. These peaks can be eliminated by means of controlling the spatial coherence of the illumination, or using a phase shifting mask that introduces a r phase difference between the adjacent holes. The filter with a narrow bandwidth introduces a pitch sensitivity and light loss into the system. A pattern can be imaged if the filter transmits the cardinal spatial Fourier components of the mask patterns. Missing components degrade the image quality. Application of such filters requires a complex optimization process that contains the evaluation of light loss, pitch sensitivity, and technical feasibility.

We discuss the theory, the experiment and applications to the interference resulting of the superposition of two or more Bessel beams propagating in free space and showed for first time a self imaging effect using nondiffracting beams.

We describe exact representations for partially coherent beams whose spectral degree of coherence remains invariant on propagation. Such beams are obtained by taking a random superposition of well-known coherent Bessel beams, each of which propagates without spreading in the transverse direction. The invariance in coherent properties for such partially coherent beams holds for propagation distances as large as the propagation distances of coherent Bessel beams.

The objective of this paper is to report the recent developments in lightweight mirror technology at Composite Optics, Incorporated. The developments are a result of the activities being conducted in support of the Next Generation Space Telescope Program. The sponsors of these efforts are the NASA Marshall and Goddard Space Flight Centers. The requirements, design approach, performance, and the technology status for the program are summarized.

Advanced technology mirrors for large space telescopes are being developed that use thin facesheets controlled by actuators. This concept was proven with a 50 cm prototype and is now being implemented for a 2-m cryogenic mirror that weighs only 40 kg.

The latest generation of astronomical telescopes is equipped by primary mirrors about 8 meter in diameter increasing demands not only of the general mechanical structure but also of the technical performances of the mirror support systems. The Large Binocular Telescope has two 8.4 meter primary mirrors supported on the same elevation mechanical structure and, each of them, located in a mirror cell enviroment. Into the latter structures hundredth of pneumatic actuators bear the weigth of the primary mirror and six positioning actuators find out the six degrees of freedom of the mirror itself, then a new control system is able to determine realtime the stiffness and the damping required by the primary mirror system. In this paper the authors describe the mechanical and the electronic active control system design and testing of the position actuator prototype that mechanically link the 8.4 m honeycomb mirror to six rigidly reinforced locations on each primary Mirror Cell structure. During telescope operation, the adjustable length of the actuators precisely control the six degrees of freedom of the mirror. Each actuator has a high mechanical axial stiffness and, as new feature, an active control system, based on piezoelectric elements and capacitive sensor, in order to control the axial stiffness versus damping, with a bandwidth from DC up to 50 Hz, assuring that the natural frequencies of the mirror do not degrade the optical performance of the telescope under external forces as the wind spectrum. Moreover, other requirements have been satisfied in the mechanic of the actuators: flexures are provided to minimize any moments applied to the attachment of the actuator to the mirror; one axial load cell for each actuator provides a precise realtime measurement of the external forces applied to the mirror, such as wind loads, to feedback the pneumatic force system that supports the weight of the mirror; a very sensitive and precise capacitive sensor measures the total length of the actuator to submicron resolution upon request. Last but not least each actuator has a reliable fail-safe system that limits the compressive and tensile forces that can be applied to the mirror. The mechanical and the electronic design DSP based and all the experimental tests of this actuator prototype have been performed in the Astrophysical Observatory of Arcetri laboratories under the supervision of the authors of this paper.

The advent of inexpensive large aperature near diffraction limited Liquid Mirror Telescopes (LMT's) makes possible applications not sensitive to their near vertical viewing nature; such as, astronomical surveys, space debris surveys, lidar collectors, and laser radiation concentrators, for plasma creation experiments in the sky. LMTs are easily an order of magnitude less expensive than a polished glass reflectors, which are only approximations to the naturally perfect parabolic surtace created by a rotating liquid. Highly reflecting liquid mercury is easily cleaned and safe when handled correctly.

The Lange Binocular Telescope (LBT) Project is an international collaboration among US, German and Italian Astronomical Institutes to build a binocular telescope with two 8.4 m primary mirrors. The LBT will have a collecting area equivalent to that of a 1 1 .8 m single dish telescope, and an angular resolution, when the two mirror are co-phased, equivalent to that of a 22.8 m telescope. The construction of the Large Binocular Telescope is in progress on all aspects. The first of the two honeycomb primary mirrors is being prepared for polishing, while the preparation of the casting of the blank for mirror two is in progress at the Mirror Lab of the University of Arizona. The structure of the enclosure is completed on Mt. Graham (AZ) and telescope pre-erection is about to start in the Ansaldo factory in Milan (Italy). Operations will start in 2002 with one of the two primary mirrors while the telescope will operate with both mirrors from 2004. The initial instrumentation will consist of four types of instruments: - twin optical spectrograph located at the direct Gregorian foci, - twin wide field optical imagers at the prime foci, - twin near infrared spectrograph/imagers at the front bent Gregorian foci, - two different interferometers, one for optical and MR wavelengths and one for near/mid infrared at the central combined foci. The twin infrared instruments and the interferometers will be designed to fully exploit the adaptive correction provided by the adaptive secondary mirrors of the telescope.

Basic principles and several key applications of wavelength tunable acousto-optic filters are described. The devices utilize periodic coupling of guided and/or dissipating modes in optical fibers provided by traveling acoustic wave in the same fiber. The wavelength tuning is realized by tuning the applied acoustic frequency, and proper phase matching condition selects filtered optical wavelength. Application of the acousto-optic filters to gain flattening of fiber amplifiers, wavelength selection, optical switching, and non-reciprocal filtering will be discussed.

A GaAs/AlGaAs in-line fiber optic filter for wavelength division multiplexing applications is demonstrated. The device consists of a GaAs/AlGaAs anti-resonant reflecting optical waveguide (ARROW) evanescently coupled to a single mode fiber. At certain discrete wavelengths, light is coupled from the fiber to the ARROW, due to phasematching conditions. Sharp resonances are observed around the design wavelength of 830 nm. The 3 dB cutoff bandwidth for TE polarization is 0.5 nm and the rejection ratio is 9 dB.

We have demonstrated the suppression of idler broadening in a two-pump fiber optical parametric amplifier by dithering the two pumps with out-of-phase signals. Idler spectrum linewidth almost the same as signal linewidth is observed.

The insatiable desire for bandwidth has compelled many technological advances in communications system components over the last two decades. Fiber optics communications bandwidth has advanced at almost exponential rates with the developments of low-loss, singlemode fibers, EDFAs, and WDM technology which uses multiple lasers on a single fiber. The SilkRoad Corporation has taken a different approach to increasing available BW by using a single, but, very stable, laser and IR photodiode detectors of unparalleled BW.

Several models have been developed to describe the interaction between neighboring ions in heavily doped erbium fibers. All of them are based on the anomalous saturation of the pump power. In this work we present experimental results of the anomalous behavior of the gain saturation in an EDFA, induced by the signal's power. This additional information shows us that energy migration is also induced by phonons.

The parameters of the transfer matrix describing a first- order optical system that is a cascade of k identical subsystems defined by the transfer matrix M, are determined from considering the subsystem's eigenfunctions. A condition for the cascade to be cyclic is derived. Particular examples of cyclic first-order optical systems are presented.

We define the pseudo-symmetrical (PS), or the non-rotating general astigmatic beams, and investigate them theoretically and experimentally. We show that to any type of symmetrical beam, such as stigmatic, aligned simple astigmatic, or rotated simple astigmatic, corresponds a type of PS beam, which we call pseudo-stigmatic, pseudo-aligned simple astigmatic, and pseudo-rotated simple astigmatic, respectively. The PS beams behave identical to the symmetrical ones as long as only rotationally symmetric optical systems are involved, and as long as the second- order moments method is used to characterize these beams. We show how to characterize the PS beams using this method, how to generate them, we study their propagation properties, and show how to identify and measure them in comparison to the measurement of the symmetrical beams.

Wave-fields that propagate in free space while maintaining invariant characteristics are important for technological applications and they are interesting from a fundamental point of view. Conditions for generalized propagation- invariant wave-fields are discussed and specific examples are presented. Propagation invariance in a limited region of space is considered as well.

We present a rigorous formalism for evaluating the degrees of freedom (d.o.f.) in communication with electromagnetic waves. We show that, although in principle there is an infinity of d.o.f., the effective number is finite. This is in agreement with the restricted classical theories. We further show that the best transmitting functions are the solutions of a specific eigenvalue equation. The analysis is valid for electromagnetic waves under arbitrary boundary conditions communicating between domains in 3D space. The practical implications of this theory will be discussed.

The propagation of Gaussian light through first-order optical systems is studied; in particular, the twist in the output (or input) plane is expressed in terms of the characteristics of the light in the other plane. Conditions are derived for which zero twist in the input plane corresponds to zero twist in the output plane, and vice versa. Three special cases for which zero twist is preserved, are described: (1) propagation between conjugated planes, (2) adaptation of the signal to the system, and (3) the case of symplectic Gaussian light.

Superresolution is attained for solar granulation images observed from the ground. The images are preprocessed with a blind deconvolution method, and then are superresolved. The resultant images show features with resolution higher than the diffraction limit.

MOMS is a live lens space camera for multispectral and stereo imaging. It was flown for the first time on a Space Shuttle mission (STS 55) in l993 in this 10-day mission approx. 7 million square km of the earth surface were covered. After the Shuttle flight the camera system was refurbished and adapted to the new environmental conditions onboard the PRIRODA-Module of the Russian MIR Space Station. Additionally, the MOMS-payload was extended by a navigation package consisting of a high precision gyro and a GPS system in order to provide the necessary position and attitude data for photogrammetric evaluation of the image data. MOMS-2P was launched into orbit in May 1996 and started its first operation in October 1996. Until end of 1998, approx. 50 million square km have been covered, mainly in the stereo mode. A tecimical description of the camera system and its operational concept will be presented as well as the present status of data recording. Information how MOMS data can be accessed and ordered will he given.

The transmission properties of an interference filter with optical gain are studied in which the layers of a gain medium are stacked in a self-similar manner. It is found that the gain variation of transmitted light with layer thickness or input frequency exhibits a fractal structure with sharp gain peaks which are not observed for a multilayer with periodic gain structures.

We present an optical setup for complete characterization of fiber Bragg gratings and wavelength selective fiber-optic devices. We measure the spectral response of these devices either in transmission or in reflection geometry, and the wavelength dependency of the group delays due to chromatic and polarization mode dispersion, as well as the wavelength dependency of the polarization dependent loss.

We describe a new method for measuring ultralow- birefringence in fibers. It is based on the fiber twist in a fiber optical loop mirror. The method allows birefringence measurement within the range from 10^-6 to 10^-8.

We propose and experimentally demonstrate a novel method which, for the first time to our knowledge, makes it possible to tailor the wavelength response of a waveguide grating coupler. Such grating couplers may be used to improve the efficiency of broad-band quantum-well infrared photodetectors and solar cells.

A novel method is described for storing and retrieving the second-order correlation function of partially coherent fields. The key element of the method is an instantaneous hologram that records the superposition of a random field whose correlation function is to be determined and the mutually incoherent reference field, taken over a time interval that is much shorter than the coherence time of the random field. The method is somewhat similar to conventional holography, but differs from it in several important respects.

New imaging method based on measuring the spatial coherence function across an observation area is presented. The propagation law of the cross-spectral density described in the Fourier domain allows us to retrieve the cross-spectral density at arbitrary reference planes. The method can be applied to a source of any state of coherence. Results of the experimental demonstration are also shown.

The light polarization and its process of propagation are mutually independent under a narrow light beam propagation through a homogeneous medium. But it is not correct for the case of inhomogeneous medium. The influence of the trajectory on the light polarization consists in the rotation of the polarization plane under light propagation along the nonpianar trajectory [1, 2]. The influence of the polarization on the light trajectory manifests itself under the total internal reflection. A linearly polarized reflected ray suffers a longitudinal shift [3, 4], and a circular polarized ray suffers transverse shift [5, 6]. It should be stressed that those investigations were independent and the effects were not considered as a result of manifestation of mutual influence of the polarization of the light and its propagation. For the first time professor B.Ya.Zel'dovich, dealing with the light propagation through a multimode optical fiber, has pointed out that the influence of the trajectory on light polarization and the influence of polarization on the light trajectory are mutually inverse effects [7]. On that base optical Magnus effect was predicted [711 and experimentally observed [8]. Optical Magnus effect manifests itself as a rotation of the speckle pattern of the circular polarized light transmitted through a multimode optical fiber under circular polarization sign change. In terms of quantum mechanics that effect was regarded as an interaction between orbital momentum of photon and its spin (polarization) [7]. All mentioned above effects exist in optically inhomogeneous medium. We can supposed that spin-orbit interaction of a photon manifests itself due to break down of the symmetry of a space, namely, the translation symmetry. Nevertheless, it was shown and experimentally observed that there exist influence of the polarization on the light trajectory under the light propagation through an optically homogeneous medium [9, 10]. That effect manifests itself under circular polarized light propagation through a half of lens: the focal spot of a beam suffers a transverse shift under circular polarization sign change. In that particular case the manifestation of spin-orbit interaction of a photon can be considered as a result of break down of the axial symmetry of a medium. That interpretation allows us to predict the existence of the inverse effect — the influence of the polarization on the light propagation in a homogeneous medium. Let us consider the propagation of the linear polarized light through a half of lens. The linear polarized light can be considered as a superposition of the left and right circular polarized light. According to [9, 10] the centers of gravity of the left and right circular polarized light will not coincide. Let us screen the half of the focal plane. The estimation based on the results [9] has shown that the transmitted light will be right or left elliptically polarized with degree of the ellipticity < iO. That scheme was experimentally realized. The change of the ellipticity of the correct sign was observed. The preliminary results were reported in [11]. That effect can be also considered as the geometric light depolarization.

In this paper, we establish the form of the spectral degree of spatial coherence of the field thermally emitted by a planar opaque surface. Our approach is based on the fluctuation-dissipation theorem. Several new properties are derived. It is shown that for lossy media, the coherence length in a plane very close to the surface is essentially the skin depth. Thus, it can be much smaller than the wavelength. However, if the metal can support a surface wave, the coherence length can be much larger than the wavelength.

We have studied the quantum efficiency of multilayer organic light emitting diodes (OLEDs). Attention is focused on the recombination efficiency and exciton quenching, controlling the performance of highly efficient OLEDs having Alq(3) (Al(III) 8-hydroxyquinoline) as the emissive layer. The kinetics model is extended to account for the image charge effect on the injection and the narrow bandwidths of carriers. An analytical criterion for maximum recombination efficiency at low voltages is found. The analysis of current voltage dependence and quantum efficiency is performed for Al/LiF/Alq(3)/TPD/ITO devices with or without an ultrathin dielectric layer LiF, taking into account the exciton quenching controlled by the boundary Al-Alq(3). We get a reasonable fit for the experimental data and discuss the optimum modifications required to enhance the device performance.

Pulsed photothermal reflection technique is developed to measure the thermal conductivity of tetrahedral amorphous carbon (ta-C) films. This technique is basically a pump and probe type. The pump source is Nd YAG laser, pulse width 8 ns, is operated at 532 nm with 1 mJ. The sample is deposited on silicon wafer and over-coated with a gold layer for heat absorption. Upon the laser pulse strikes on the sample surface, the surface temperature rises sharply and then relaxes with time. A continuous HeNe laser (1 mW) probes the surface temperature, measuring the reflectivity changes on the sample's surface. Since the reflectivity and temperature has an inverse linear relationship, the relaxed temperature profile can be obtained by inverting the captured reflectivity profile. Using either 2-layer or 3-layer heat conduction model, thermal properties of the ta-C film are then varied to fit the obtained profile. The fitted thermal conductivity value of the ta-C film is approximately 2 W/mK.

Oriented polycrystalline polymers with high mechanical properties are very important for many practical applications. Such materials can be produced by drawing at temperatures near to their melting point. During the drawing process, macromolecules are aligned along the drawing direction, which leads to a considerable increase in the Young's modulus, strength and stiffness of polymer. The orientation distribution function of macromolecules is one of the most significant characteristics of the structure of oriented polycrystalline polymers. The coefficients of the distribution function expansion in a series of generalised spherical harmonics can be determined by several techniques, such as X-ray analysis, IR-spectroscopy, and birefringence measurements. Raman spectroscopy is one of the most convenient and informative tools for studying the orientation of macromolecules. It has been shown that Raman spectroscopy is capable of determining the expansion coefficients up to the fourth order for both crystalline and amorphous phases [1,2]. At present, Raman spectroscopy is often used to study the orientational order in a various polycrystalline polymers (see references from [3]). Here we present the investigation of mechanism of uniaxial deformation of polyethylene from the isotropic state to the extremely drawn state (when increasing the draw ratio causes the sample to break apart).

In the present work some results of modulation peculiarities measurements of linearly polarized laser beam are obtained. The laser beam with polarization under 45 degree(s) angle to the optical axis of quartz passed through quartz crystal set between two crossed polarizers. The intensity of laser beam after passing through the polarizer-crystal-analyzer system was measured in dependence of the turn angle of crystal. It is determined that every pair of parallel faces of quartz cube has its individual modulation intensity picture. Experimentally conditions do not influence the whole picture. It is supposed that different kinds of modulation can be connected with certain crystallographic directions.

In this contribution examples of the optical characterization of multilayer systems with randomly rough boundaries are presented. The method based on measuring and interpreting the spectral dependences of the coherent reflectance is used to determine the values of the optical and statistical parameters of samples of three-layer and thirteen-layer systems exhibiting the rough boundaries. The systems mentioned are formed by thin films of SiO₂ and TiO₂.

There are reviewed and summarized several theoretical models describing various mechanisms of developing of laser-induced temperature and field instabilities in both absorbing and nonabsorbing microinclusions. Most attention is paid to application of the models to investigation of laser-induced damage. General criterion for evaluation of damage threshold is deduced from presented models and discussed.

Dispersion-managed solitons exhibit superior transmission quality as soon as Kerr nonlinearity in non negligible. Long transmission distances, large span loss and high spectral efficiency are expected for the next generation of transmission systems based on 20 Gbit/s and 40 Gbit/s data rate.

We report the development of a lab prototype for all optical synchronization at 10 GHz. Adjusting the distance between the AR coated facet of the MQW semiconductor laser and the ferrule it was possible to induce the self-pulsation needed for correct operation. In the presence of optical RZ signals, the device leaves is natural pulsation frequency synchronizing with the input data.

We examine the main constraints on the design of single- channel, high-bit rate soliton communication systems. In the average soliton regime, the main limitation for transoceanic fiber links is the Gordon-Haus jitter, while for shorter transmission distances it arises from the discrete in-line amplification. The use of dispersion-decreasing fibers and of periodic optical phase conjugation can increase the system capacity.

After a short introduction on the European Union RTD Programs, a more in-depth analysis will be given on the projects and results recently obtained within in the ACTS (Advanced Communications and Services Program) Photonic Technologies Area.

We discuss methods of image reconstruction which lead to non-negative images: no negative values appear in the estimate or approximation to the unknown object. We describe methods which always lead to non-negative estimates of the object, characterize some regularized and non-regularized methods, and characterize those orthonormal systems whose partial series approximations to the object are always non- negative. This paper surveys the authors' recent research, adds some new results, and discusses related work.

The shift-and-add (SAA) method is applied to specklegrams of solar granulation to reconstruct its high-resolution image. The SAA recovers solar granulation from the atmospherically degraded images. From our reconstruction result it is shown that SAA method is useful for a largely extended object.

Hybrid holographic microscopy, in which a hologram of a microscopic object recorded by an image sensor is numerically reconstructed using a computer, can provide 3D information of an object. This study proposes a new 3D reconstruction technique using a slant.

There are several known iterative algorithms, which reconstruct the phase of an unknown wavefront from two intensity measurements. These algorithms are based on a Fourier connection between the input and output plane. An algorithm based on a Fourier connection must contain additional optical setup for the implementation and in addition needs more longitudinal space. Since a wavefront is a function that obeys the wave equation, it is only natural to implement the iterative algorithms using free space propagation relation between two intensity planes. We propose to make phase retrieval calculations between any two arbitrary planes interrelated through the Fresnel domain. Since any two arbitrary parallel planes are interconnected by the Fresnel domain, no additional setup is needed. The calculation of the free space propagation is based on the angular spectrum approach, which is calculated using the fast Fourier transform. This approach can be applied with any of the algorithms that rely on a Fourier connection between the input and the output planes.

In image acquisition, the captured image is often the result of the object being convolved with a blur. Deconvolution is necessary to undo the effects of the blur. However, in reality we often know very little of its exact structure, and therefore we have to perform blind deconvolution. Most existing methods are computationally intensive, Here, we show that if the blur is symmetric, we have an efficient algorithm for deconvolution based on polynomial factorization in the z-domain.

We exploit the random superposition process for presenting a statistical model that describes the reduction of multiplicative noise, on a periodic structure, by using the self-image phenomenon. We discuss a novel, noncoherent, optical processor for visualizing this reduction process, in a single picture. Numerical simulations are reported.

A single frame phase-shifting speckle-interferometer for quantitative measurements of out-of-plane-deformations is presented. Using a diffractive optical element, six phase- shifted interference patterns are generated and stored within the frame time of a single CCD-camera.

Multiple wavelength interferometry is used to increase the range of unambiguity beyond that of single wavelength interferometry. In wavelength scanning interferometry, the frequency of the intensity modulation induced by the wavelength change is determined independently for each image pixel. The tuning range determines the resolution of measurements, while the tuning step limits the range of the measurements. Laser diodes can be tuned, but an external cavity is needed for a larger mode hop free wavelength variation. Polished and optically rough surfaces can be analyzed in the same manner. Acquisition times of a few seconds and high resolutions were obtained. In a new development, the application of temporal evaluation of speckles for deformation and shape measurement will be discussed. It turns out that spectral and temporal phase analysis can be very useful for many applications in optical metrology.

Stringent surface specifications for highly reflective precision optical surfaces place great demands on interferometric techniques used for surface metrology. Highly reflective test surfaces often produce nonsinusoidal interference fringes when compared to a partially- reflective/absorbing reference surface in Fizeau-type interferometers. This talk will discuss some tradeoffs in choosing phase-measurement techniques for use with noticeably nonsinusoidal fringes when the residual measurement error needs to be on the order of one-hundredth of a wave peak-to-valley. The errors due to the phase calculation algorithm, the phase shift calibration and the reference surface calibration are all coupled making the choices more difficult. Simulated data will be used for most of the discussion. Comparisons to the measurement of uncoated surfaces will be made.

Phase-shifting property of moire patterns which constitute spatially sampled data set of single interferograms with a linear carrier is revealed. Based on this property, a phase reconstruction method using the phase-shifting algorithm is proposed for single interferograms with a linear carrier. Limits of a carrier frequency and a phase slope being reconstructed are given.

Optical interferometers are being built to operate over longer and longer baselines, in some cases more than a few kilometers. Examples include laser interferometers to detect gravitational waves, and stellar interferometers which use starlight to determine the angular diameter of the source. The optics used in these interferometers must satisfy demanding performance criteria. In this paper we review some of those criteria and present results which demonstrate that such optical surfaces can be successfully fabricated and measured.

We demonstrate 22 fs pulse generation from a unidirectionally modelocked Ti:sapphire ring laser at a repetition rate of 1.5 GHz. Intracavity dispersion control is accomplished by dispersive mirrors.

Fourier synthesis of 257-GHz optical pulse trains has been demonstrated based on optical phase locking of three independent continuous-wave semiconductor lasers using SOA as a four-wave mixer. The FM sideband heterodyne technique was employed to ensure the stable homodyne optical phase locking. The SHG correlation traces were measured for several phase-locking offsets, and were in good agreement with theory.

We discuss Fourier optics methods for ultrafast optical pulse shaping, waveform synthesis, and signal processing, which are achieved by spatial manipulation of the dispersed optical frequency spectra of femtosecond pulses.

We have used picosecond ultrasonics techniques to study the localized surface vibrations in Mo/Si multilayers. Two band- gap modes were simultaneously detected using a new alternating pumps scheme, which has been demonstrated to enhance the signal-to-noise ratio by 10 dB.

We investigate the effects of time delayed nonlinear absorption (Raman effect) on spatiotemporal propagation for femtosecond pulses. In the case of normal dispersion and no Raman effect, we find symmetric pulse splitting, in agreement with previous work. However, as the magnitude of the Raman effect increases relative to the dispersion, asymmetric splitting occurs. For significant Raman effect, the pulse splitting due to GVD is suppressed.

The optical correlator is considered as an effective type of coherent optical processor with parallel way of data processing. Two basic schemes of the optical correlator are known: one with frequency plane (or Vander Lugt correlator) and second one with the joint Fourier transformation. The authors of the given work are concerned with a problem of the pattern coding and recognition for a number of the static images.

The morphological correlation has been recently used as a tool in optical pattern recognition owing to its nonlinear properties. In this paper, we present an extension of the morphological correlation to color pattern recognition. We use two methods: the multichannel one, based on decomposing the image in separate channels, and the single channel method, based on codifying the color information into a single amplitude/phase distribution. Simulation results are given and optical implementation is proposed.

An improved multiple target detection technique is proposed by using a wavelet joint transform correlator (JTC). A bank of wavelet filters are generated using the Mexican hat wavelet function which are sequentially superimposed on the joint power spectrum before applying the inverse Fourier transform to yield the correlation output. This technique is found to yield high correlation discrimination for multiple target detection for both binary and grey level input scenes while avoiding the false alarms as well as rejecting the non-target objects. An all-optical implementation for the proposed wavelet JTC technique is also suggested. Computer simulation results are presented to confirm the effectiveness of the proposed technique.

Synthesis of gray level computer generated holograms allows to increase the information storage capability of complex filters. In this work we study the capability of gray level filters to perform multichannel correlation. To this end a composed synthetic discriminant function filter is employed to implement an object classification by means of a binary code.

Volume holographic associative storage in a photorefractive crystal provides an inherent mechanism to develop a multichannel correlation system with high parallelism. Wavelet transform is introduced to improve recognition accuracy of the system. A novel volume holographic correlator is proposed and constructed. Its application in human face recognition is studied, and experimental results are given.

We present theoretical analysis and experimental results of a white light JTC (joint transform correlator) using a tri- color grating to encode color patterns. The power spectra of the encoded pattern are easy for parallel channeling, and the zero order power spectrum also forms an important channel for the shape-only correlation.

As is well known, the spatial coherence in a speckle field is limited to an area called the mean speckle size. Throughout this area, the coherence decays smoothly from the center to the margin of a speckle, and the degree of coherence between two points (x₁,y₁) and (x₂,y₂) determines the probable amount of deviations between their intensities I₁, I₂ and phases. These deviations are of special importance when spatial phase shifting is applied in electronic speckle pattern interferometry. We demonstrate that the knowledge about the intensity and phase gradients in the object speckle pattern can be used to reduce the noise in measured deformation maps significantly.

The paper presents the main techniques that were developed in the last years to measure high speed transient displacements using double-pulsed video speckle interferometry.

A novel feedback interferometer, which consists of a polarization Sagnac interferometer and an optically- addressed phase-only spatial light modulator, is described for real-time and unambiguous visualization of the surface profile. In this system, the output intensity from the Sagnac interferometer is optically fed back to the phase modulator placed in one arm of the interferometer to produce a sawtooth fringe intensity profile which is directly and unambiguously related to the surface profile. Experimental results demonstrate the feasibility of applying this system to surface profile measurement.

The basis of the described 3D-measurement system is the method of fringe projection in combination with the principle of uniform scale representation /1 1, /2/, /3/. The measurement is characterized by the exclusive use of phase-measurement values for the coordinates of each point. To obtain the phase-measurement values the object under test is successively illuminated with a grating structure from at least three different directions with a telecentric system. A CCD-camera records the intensity distribution of the fringes intersected by the object. It should be pointed out that the values of all coordinates (x,y,z) have the same accuracies. The object to be measured and the CCD-camera are both mounted on a rotation table, turning both of them with respect to the fringe-projector about an axis. The rotation axis makes a constant angle c with the projection direction. With at least i = 3 different angle values e the linearly independent absolute phase values are obtained, which are necessary for the coordinate calculation (applying gray-code in conjunction with four 90 degs phase-shifts). In our setup we can choose up to I = 1 5 rotation angles, so that awkward areas of the surface, like zones with either specular reflection or shadows, are shifted over the surface and have nearly no influence on the results of measurements. So, we obtain the 3D-coordinates of a single patch of the object. We have expanded the system to include a second rotation axis, where the object can rotate within the measurement volume. The CCD-camera will then get different views of the object. The second rotation axis is tilted against the first axis by an angle S. Depending on the class of objects there are different possible tilt-angles S. Typically we choose ö = 300. By rotating the object around the first axis with a rotation angle -y (j = number of patches) it is possible to measure the object from different viewpoints, whereby for each patch or viewpoint the procedure described above is used. For a convenient handling of the data-set the restriction j 8 is used. The actual rotation angles e and y were measured with angle encoders. The free geometric parameters (grating periode A and projection angle a) and the orientation in space of the second axis are gauged before the measurement procedure as described below. By measuring a number of patches we have the problem of transforming them from a local coordinate system into a global one. The combination of the different patches into one coordinate system without interactive user help was solved by developing a calibration method for the second axis. In combination with an absolute phase measurement all patches were measured in a known space orientation, so that we obtain the 3D-picture by rotation of each patch around the second axis. Correlation methods or special points are not necessary. To obtain the 3Dorientation of the second axis one can use a calibration procedure with a special calibration body whose 3Dcoordinates are measured for different rotation positions whereby the second axis has to cross the plane near the centre.

The first known lenses appeared during the IVth and Vth Dynasties (fabricated mainly between ca. 2500 - 2400 BC) of the Old Kingdom of Egypt. Excellent examples of these lenses are found in The Louvre Museum in Paris and the Egyptian Museum in Cairo. These lenses were components of eye constructs in statues and had unique qualities. In particular, the `eyes' appear to follow the viewer as he/she rotates about the statues in any direction. Clearly, this was an intended effect which can be readily photographed (and understood optically). The lenses were ground from high quality rock crystal (a form of quartz). They had a convex and highly polished front surface. On the plane rear lens surface as `iris' was painted. Centered in the dark- appearing pupil zone was an approximately hemispheric negative ground, high power, concave lens surface.

Optical tweezer is a powerful tool for manipulating samples under a microscope. However, this technique is limited to transparent objects because it has been believed that it is the light refraction that play a significant role to manipulate the microscopic objects. We took notice of a optical force generated by a surface diffraction wave, so called creeping wave [1] , and found that it can be applicable to trap metallic objects [21. In this presentation, we show that gold Mie particles (0.5 - 3.0 im in diameter) can be trapped optically in two dimensions.

We propose a new approach for the 2D-space-to-time conversion by using spectral holography. In this approach, we assign procedures for the 2D-space-to-time conversion to processing in spatial and temporal domains in order to avoid the influence of the optical power loss in transmission process.

Today, ultrafast laser technology demonstrates unsurpassed performances in terms of pulse duration, pulse repetition rates, average power and wavelength range. This enables new applications in many areas such as optical communication, photonics switching, RGB-displays, material processing and many more. These markets will strongly drive further research efforts towards even more reliable and more compact sources. In addition, we are at the edge of sub-femtosecond science using high-harmonic generation of optical pulses with only few optical cycles.

We have studied sub-optical wavelength atomic gratings generated by the interference of atomic de Broglie waves in a time-domain interferometer. Three short optical standing- wave pulses, detuned from resonance with a cloud of approximately 100 (mu) K ⁸⁵Rb atoms, act as phase gratings for atomic matter waves. Shortly after the first pulse, a modulation in the atomic density containing spatial harmonics of period (lambda) /2N appears ((lambda) is the optical wavelength, and N is any integer) and then rapidly vanishes due to the atomic thermal motion. The cloud maintains phase memory of this modulation, however, and the second pulse (applied at time T after the first one) results in a temporal sequence of atomic density gratings of periods (lambda) /2N. The appearance of a grating is referred to as an echo. The third pulse (and a subsequent traveling wave pulse) is used to detect these gratings. By this technique, we have created and detected in real time a grating with period (lambda) /4 at time 1.5T after the first pulse and observed new types of `echoes' caused by interaction of the de Broglie waves with all three phase gratings. This ability to produce sub-wavelength structures makes our techniques applicable to atomic beam lithography.

Experimental results on phase-space imaging of a laser- cooled atomic cloud are presented. Both position and velocity information are encoded in the frequency of the signal coherently radiated from the cloud. This encoding is achieved by application of a position-dependent magnetic field. Fourier transformation of the signal yields a projection of the phase-space density of the atoms. Imprinting a structure on the cloud we observe its time `sheering' evolution in the phase-space. Since the projection direction is determined by the imposed field gradient, we can reconstruct the phase-space structure of the cloud.

TRANslucent Smart Pixel Array (TRANSPAR) systems perform high performance parallel pipeline networking and signal processing based on optical propagation of 3D data packets. The TRANSPAR smart pixel devices use either self-electro- optic effect GaAs multiple quantum well modulators or CMOS- VCSEL-MSM (CMOS-Vertical Cavity Surface Emitting Laser- Metal-Semiconductor-Metal) technology. The data packets transfer among high throughput photonic network nodes using multiple access/collision detection or token-ring protocols.

VLSI smart pixel arrays are being developed for free space optical interconnects in high density input/output applications. An individual smart pixel cell, which operates at 850 nm, consists of a vertical cavity surface emitting laser, a photodetector, an optical receiver, a laser driver, and digital logic circuitry. For optical interconnect applications, the integrated smart pixel combines high speed operation and low power consumption. A 32 X 32 smart pixel array is currently being developed that will operate at 500 Mbps/channel, which gives an aggregate throughput of > 500 Gbps with a power consumption of < 10 W.

We present a system in which it is possible to distort the intensity distribution of an object I(x,y) into I(Ax + By,Cx + Dy), where the ABCD matrix has a unit determinant. The coefficients A, B, C and D can be varied independent of each other by rotating some cylindrical lenses. The degree of coherence is arbitrary. The number of pixels is limited in the usual way by the size of the object, by the wavelength, and by the F-number of the lenses.

From the view point of neural networks (NNs) the present problems of optical correlation pattern recognition (OCPR) are analyzed. It is shown that distortion invariant pattern recognition (DIPR) can not be performed with a single filter within the framework of OCPR. By means of fusion between OCPR and NNs some solutions to an effective optical DIPR are proposed.

The National Ignition Facility (NIF) is a 192 beam, 1.8 megajoule laser currently under construction at LLNL. The laser requires approximately 7,500 meter class optical components including 3,000 phosphate laser glass slabs, 2,500 fused silica lenses and windows, 1,400 BK-7 mirror and polarizer substrates with hafnia/silica multilayer coatings, and 600 KDP and deuterated KDP (DKDP) nonlinear crystals, each component with a 40 cm square aperture. These optics will be produced between 2000 and 2003 following pilot production campaigns to prove the technologies in 1999. The specifications of these large optics are challenging, with a typical wavefront gradient of Xi90/cm RMS,and damage thresholds of 14 J/cm2 (351 nm) and 20 J/cm2 (1053 nm) for 3 ns pulses. The cost goals for producing each of these optics vary, but on average are approximately three-times lower than we paid for Beamlet and Nova optics.

The use of lasers as the driver for inertial confinement fusion experiments and weapons physics applications is based on their ability to produce high-energy short pulses in a beam with low divergence. Indeed, the focusability of high quality laser beams far exceeds alternate technologies and is a major factor in the rationale for building lasers for such applications The National Ignition Facility (NIF) is a large 192-beam laser facility now under construction at the Lawrence Livermore National Laboratory for fusion and weapons physics experiments. Its uncorrected focal spot minimum size is limited by wavefront aberrations in the laser system. NIF is designed with a wavefront control system to correct these aberrations to yield a focal spot that is small enough for NIF' s intended applications. Sources of aberrations to be corrected include prompt pump-induced distortions in the laser amplifiers, thermal distortions in the amplifiers from previous shots, beam off-axis effects, and gravity, mounting, and coating-induced optic distortions. Aberrations from gas density variations and manufacturing figure errors in the optics are also partially corrected by the wavefront control system. The NIF wavefront control system consists of five subsystems for each of the 192 beams: 1) a deformable mirror, 2) a wavefront sensor, 3) a computer controller, 4) a wavefront reference system, and 5) a rapid reconfiguration system to allow the wavefront control system to operate to within one second of the laser shot. The system includes the capability for in situ calibrations and operates in closed loop prior to the shot. Shot wavefront data is recorded. This paper describes the function, realization, and performance of each wavefront control subsystem. Subsystem performance will be characterized by computer models and by test results. The focal spot improvement in the NIF laser system effected by the wavefront control system will be characterized through computer models. The sensitivity of the target focal spot to various aberration sources will be presented. Analyses to optimize the wavefront control system will also be presented.

A technique for testing aspherical surfaces without the use of a null-corrector is described. The wave-front sensor for the detection of the aspherical wave-front is a Shack- Hartmann sensor which has a significantly expanded range of measurable wave-front slopes. The optical testing set-up, the used algorithm for the dynamic range expansion, and experimental results are presented in this paper.

The design of devices, components or systems using optical fibers and integrated optical waveguides, involves the solution of the wave equation under specific boundary conditions. Although in some situations one can obtain analytical solution to the problem, in most cases the problem needs to be tackled numerically. For example, in devices using graded index waveguides or bent waveguides, in general one cannot obtain analytical solutions. In order to tackle such problems many numerical techniques have been developed in the literature. The matrix method which forms the subject matter of this talk is one such method developed by us. This method has been used for obtaining the propagation characteristics of planar graded index waveguides, bent planar waveguides, cylindrical optical fibers with an arbitrary refractive index profile and quantum well structures. One of the most important attributes of this method is the fact that this method can yield complex propagation constants of an optical waveguide without performing any complex plane iterations and hence can be used as a method to predict starting values in any complex plane iteration program. Using this technique one can also obtain the leakage losses in waveguides and in particular in depressed cladding fibers.

We report experiments on cw parametric oscillation in AgGaS₂ and spectroscopic characterization of Yb³⁺ doped AgGaS₂.

We demonstrate a new kind of picosecond laser source in the UV at high repetition rate. This system is based on only passive, compact and simple elements: a microchip laser and a very efficient multipass amplifier both pumped with recently developed high brightness laser diodes. This all- solid-state laser has been optimized for delivering, at a high repetition rate -45 kHz-, sub-nanosecond pulses at the wavelength of 355 nm with an energy per pulse close to 1 (mu) J (or equivalently 38 mW average power). This source is- -to our knowledge--the first totally passive, 300-ps UV laser source at this high repetition rate.

Some aspects of the propagation of femtosecond laser pulses in transparent, dispersive, nonlinear media are reviewed. Since the details of pulse propagation depend critically on the experimental conditions we only will briefly consider a general case of a femtosecond wavepacket evolution and then apply it to specific problems. Theoretical and experimental results for wavepacket distortion by lenses and wavepacket distortion in birefringent media will be presented. Splitting of femtosecond wavepackets in dispersive Kerr media will be also discussed.

Upconversion lasing of a thulium-ion-doped zirconium fluoride glass microsphere was demonstrated. The microsphere was pumped by a fundamental wave of a Nd:YAG laser (1064 nm) at room temperature. The lasing emission was observed in 480-nm and 800-nm regions, and their lasing thresholds were determined to be approximately 20 mW and approximately 5 mW, respectively. The application to near-field optical microscopy is also discussed.

We experimentally observed the unusually fast response in a two-wave mixing arrangement with fiber-like Bi₁₂TiO₂₀ crystals on transient change of the external electric field. Pulses of the amplification of the signal wave with a rise time down to 0.2 ms and a width of 0.5 ms at a total input intensity of 6 mW/mm² are obtained when applying a rising or decreasing front of an external electric field to the crystal. The two-wave coupling without external field has a response time of 200 ms.

It is generally recognized by the optics in computing community that photonic technologies can help to alleviate the data communication bottlenecks of future digital processing systems in two ways. In a first approach optics could be used as a wirereplacing technology at the different interconnect levels in computers such as the back-plane, the board-to-board, the multi-chip to multi-chip (MCM) and even the intra-MCM interconnect level. In a second approach 2D-arrays of smart pixels, which are integrated VLSI-photonic components that combine the electronic processing power of Si-CMOS with the high interconnect density of GaAs-based parallel opto-electronic I/O planes, could play a major role in dedicated processing systems such as smart focal-plane arrays, artificial retina and early-vision processors and outperform their dedicated all-electronic counterparts. In this paper we bring forward some of the multifarious ways to put micro-optical components to work in digital optical information processing systems by reviewing two of our most recent proof-of-principle demonstrators. First we will illustrate the "microoptics as a wire-replacing technology" paradigm by presenting a micro-optical module for multi-channel free-space intra-MCM interconnects. Secondly, as an example of the so-called "smart pixel" paradigm, we demonstrate how we have constructed a prototype morphological image processor based on 8x8 arrays of opto-electronic transceiver arrays

Recently, there has been considerable interest in the application of combined phase/amplitude encryption to the field of optical pattern recognition based security systems, due to the high level of security that it offers1. We have developed a new phase-only encryption technique based in principle on a phase-coding method which uses a generalization of the Zernike phase contrast technique, but breaks the small-phase-angle limitation of Zernike's method2. This phase-coding technique for image formation, in which the spatial average value of an input phase modulated image is combined with a pre-estimated phase retardation produced by a phase contrast filter, has been demonstrated experimentally3. In this paper we describe an extension of our phase-coding method4 and its application in an experimental system for the decryption and visualization of phase encrypted images using commercially available Parallel-Aligned Liquid Crystal Spatial Light Modulators (PAL-SLM) supplied by Hamamatsu Photonics5.

The thresholding scheme in which a person can decode the encrypted data with an important information in the agreement of other members has been extended to the visual data by visual cryptography. But with the limitation of visual cryptography in the representation of information, some problem is encountered in application. This paper proposes a method to overcome the problem by introducing an optical technique to the visual cryptography.

An anti-counterfeiting method using CGH phase coding is presented in this paper. The phase of a wave-front is coded by means of detour phase coding and then interfere with a reference wave, which is also generated by CGH. The object recorded in the hologram can be read out from the interference patterns. The object can be easily generated by computer, caught by CCD camera or scanner, both black-white and grayscale object can be used in our method. The features of this method lies in that it is flexible in designing, easy to observation and reconstructed by common expanding white light source. The reference wave can be a plane wave or another phase coding wave, then it's difficult to duplicate an identical CGH based on the decoding information, this made it enjoy a high anti-counterfeiting ability.

A two-step carry-free negabinary signed-digit (NSD) addition/subtraction algorithm and the fast conversion algorithm from NSD to negabinary in the carry-look-ahead mode have been investigated. All the arithmetic operations can be performed with binary logic. By programming the binary reference bits, addition and subtraction can be realized in parallel with the same binary logic functions. Correspondingly, a compact general-purpose optoelectronic arithmetic-logic array system using electron trapping device is suggested. Various complex logic functions can be performed by programming the illumination of the data arrays without additional temporal latency of the intermediate results. Experimental results will be presented.

We discuss the design of diamond turned mirror to be used to certify a refractive null corrector to test a 6.5 meter, F/1.25 paraboloidal mirror. Practical details of the certification implementation will also be presented.

It is analyzed a mechanically compensated zoom lens in which the second and fourth components are movable to attain zooming effects, while the first, third and fifth components are fixed during zooming. It is derived a set of quartic and two (or four) elements simultaneous zoom equations each of which simultaneously satisfies two paraxial conditions; continuous change of magnification (or focal length) and constant object-image distance. Analytical solutions are obtained together with an approximate zoom equation in the vicinity of a critical point and that near a singular point. Numerical example is added to show the effectiveness of the analysis.

The new design for the prism based refractometer sensor presented here is characterized by its high sensitivity over a wide range of refractive indices of the ambient. The refractometer is more robust and user friendly than other such refractometers reported in literature.

The test of rod-like technical objects can be carried out in grazing incident using diffractive optical elements as beam splitters and at the same time as generators for master wave fronts. The occurring interference patterns can be evaluated with the help of the well known phase shifting technique. Wave aberrations caused by the adjustment state of the test sample can be removed from the data set via least squares fitting a functional representing the wave aberrations due to misalignments.

Collimation of beam is essential in long path interferometry otherwise significant measurement error may be introduced. Therefore, considerable efforts were spent in developing techniques of collimation testing. In laser interferometers, the source is effectively a point. However, its axial shift from the focus of the collimator introduces a curvature in the wave front and its lateral shift may introduce off-axis aberrations. Therefore, the objective is to place the point source at the focus of the collimator. This task is achieved by collimation testing techniques, which can be grouped under interferometry, shear interferometry, Talbot interferometry, and phase conjugate interferometry. We will discuss these techniques below.

Low-frequency fluctuations in semiconductor lasers with optical feedback both from short and long external cavities are investigated. At a modulation frequency which is very close to the external cavity mode, low-frequency fluctuations are eliminated and frequency-locking to the modulation in the laser output power is found.

Low frequency fluctuations similar to those observed in experiments are found in a model that includes explicitly carrier diffusion and lateral profiles for the carriers and the optical field. We compare with the predictions of the standard model, that includes lateral effects phenomenologically though an additional gain saturation term.

The vertical cavity surface emitting laser (VCSEL) [lJ is meeting the 3rd generation of development in 1999 and the deadline of the S. Y. Wang's prophecy is approaching a few years ahead. Actually, it has been being applied into various optical systems such as optical networks, parallel optical interconnects, laser printers, high density optical disks, and so on. We like to review the progress of VCSELs in wide spectral ranges covered by various 111-V compound semiconductors. Some innovating technologies will be discussed.

The intriguing polarization properties of Vertical-Cavity Surface-Emitting Lasers (VCSELs) are discussed and different physical mechanisms to explain this behavior are proposed. Experimental results obtained on different types of VCSELs will be confronted with the predictions from different theoretical models.

The experimental evidence of Stochastic Resonance in the polarized emission of Vertical Cavity Surface Emitting Lasers is given. We report for the first time in an experimental work a complete characterization of the phenomenon based on the residence times probability density. We give also the evidence of the bona fide resonance, clarifying this recently debated subject.

Optical pattern recognition and in particularly optical correlation has been the subject of intensive research for many years. The basic principle consists of the comparison of a reference image with the scene to analyze. The potential advantage of optical technologies is their ability to determine the conelation function very rapidly. Most of the research effort has concentrated on technology, and particularly on the spatial light modulators (SLM) which enable to encode the reference and the input images on a coherent optical beam and on the detectors. The recent availability of efficient SLM's and fast detectors has allowed the realization of different [1,2,3] optical correlator demonstrators and the question of their practical fields of applications becomes more stringent.

This paper gives a concise summary on recent progress of our research on an incoherent optical correlator based optoelectronic human face recognition processor. Several methods for improving its processing speed, discrimination ability, and robustness are illustrated.

Wood quality is of great importance for all of forest industry, because it affects on suitability of wood as raw material for the wood processing industry. In the future, the aim will be to use the right materials for the right end products. For this purpose we need to understand how the material properties of wood are distributed in the stem, and how the properties of wood vary from a tree to tree and from a stand in relation to the genetics, site properties and silvicultural history. Currently, detailed information is lacking how genetic, environmental and forest management influence wood properties (i.e. between and within ring variation). This is although, for example, wood density and equally percentage of latewood, which is known to reduced by faster diameter growth, i.e. larger proportion of earlywood. Wood density reflects also the amount of cell wall material, and it is considered as a key property. It also correlates to other properties of the wood like strength (important for mechanical industry) and pulp yield in terms of the quantity of chemical and mechanical pulp obtained from the volume unit. For the pulp and paper industry, the earlywood/latewood ratio is respectively of great importance, because latewood tracheids of softwoods have thick walls, which increase the density and mechanical strength of wood. On the other hand, considerably more energy is needed in defibration of latewood than earlywood.

The use of circular harmonic filters for the invariant recognition of marine microorganisms is presented.

Normalized correlation provides a way to achieve reliable pattern recognition with images containing multiple target objects of unequal intensities without the need of image segmentation. We show that the optimum Bayesian processor for the detection of a target with additive correlated noise and disjoint background, introduced, has the form of the normalized correlation. In consequence it can be expressed with correlations and pointwise processing only--which is a condition for an efficient optical implementation. Moreover it may be applied to multi-object intensity invariant problems.

Babinet's principle establishes the equivalency from the diffracting fields by complementary gratings. In this work there is shown results obtained by the diffracting field of different orders of Cantor's and Sierpinski's Fractals and their complementary, according to Babinet's principle, observed experimentally and computer simulations. The agreement of results is excellent.

Speckle patterns having fractal properties are produced in the image plane as well as in the diffraction regions of a planar diffuser. Such a pattern has no definite speckle size and exhibits a statistical self-similar feature within a limited extent. The intensity correlation function is shown to obey a power-law, which is a typical property of fractal distributions.

We propose a new method for direct control of position, rotation, and scaling of fractal patterns generated on the optical fractal synthesizer. In this method, we introduce IFS mother function to generate control parameters for arbitrary fractal patterns. We implemented the method experimentally and verified effectiveness of the method.

A plate with constant thickness was designed to compensate for the residual distortion in the image projected by a high-quality projection lens for lithography. The two surfaces of the plate have an identical aspheric profile whose shape has been calculated using the measured distortion map of the lithographic objective. The figuring process applied to the plate uses the principle of polishing in the presence of an elastical deformation to achieve the desired aspheric shape on both sides. A description is given of the subsequent process steps and of the obtained surface accuracy.

The history of optical lithography is reviewed as a basis for discussing its future. The key methods used so far to boost the resolution are: the use of a higher numerical aperture, reduction of the exposure wavelength, and the introduction of resolution enhancement technologies. For the continued use of optical lithography in the future, the exposure wavelength must be reduced. The two approaches to doing this--a gradual reduction and a sudden, large reduction--are compared.