KEYWORDS: Holography, Holographic data storage systems, Data storage, Modulation, Servomechanisms, Digital video discs, Reflectivity, Mirrors, Digital holography, Digital recording
Collinear holography has been good candidate for a volumetric recording technology of holographic data storage system (HDSS), because of there are not only large storage capacities, high transfer rates, but also the unique configuration, in which the information and reference beams are modulated co-axially by the same spatial light modulator, as a new read/write method for HDSS are very promising. The optical pickup can be designed as small as DVDs, and can be placed on one side of the recording media (disc). In the disc structure, the preformatted reflective layer is used for the focus/tracking servo and reading address information, and a dichroic mirror layer is used for detecting holographic recording information without interfering with the preformatted information. A 2-dimensional digital page data format is used and the shift-multiplexing method is employed to increase recording density. As servo technologies are being introduced to control the objective lens to be maintained precisely to the disc in the recording and reconstructing process, a vibration isolator is no longer necessary. In this paper, we introduced the principle of the collinear holography and its media structure of disc. Some results of experimental and theoretical studies suggest that it is a very effective method. We also discussed some methods to increase the recording density and data transfer rates of collinear holography using phase modulated page data format.
We have demonstrated remarkable enhancement of longitudinal and transverse magneto-optical Kerr effects in magnetoplasmonic crystals based on thin nanostructured films of nickel and iron due to resonant excitation of magnetoplasmonic waves in Faraday and Voight configurations . Manifestations of ultrafast time-dependent transverse magneto-optical Kerr effect are experimentally demonstrated in femtosecond laser pulses reflected from a one-dimensional magnetoplasmonic crystal. We show that exciting surface plasmon-polaritons with magnetization-dependent dispersion law allows one to control the shape of the refected pulse.
A one-dimensional photonic crystal with termination by a noble metal film–a plasmonic photonic-crystal slab–has been
theoretically analyzed for its optical response at a variation of the dielectric permittivity of an analyte and at a condition
simulating the molecular binding event. We investigate sensing performance by the slab and show that it is tolerant to
the variation of probing conditions and the slab's structural parameters. As a consequence, the considered sensor
exhibited an enhanced sensitivity and a good robustness in comparison with conventional surface-plasmon and Bloch
surface wave sensors.
A compact optical correlator that can retrieve shape, color, and texture information was improved and optimized for
medical applications. Some optical components of the optical correlator were changed to eliminate stray light. Tumor
and normal cell images from rats can be clearly distinguished by using their color and luminance information. Here, the
color and luminance data from the cell images were converted into two-dimensional patterns on the x-y chromaticity
diagram and the luminance histogram, respectively. The tumor cell images were clearly distinguished from large
numbers of cells by retrieving the color and luminance patterns. Based on these results, we have demonstrated that our
optical correlator is an effective tool for retrieval of complicated large volume information, such as that of cell images.
A compact optical correlator applicable to the retrieval of colour and texture as well as shape information was developed.
A new technique for retrieving colour and texture information by using a slot-in-type compact joint-transform correlator
(JTC) with minimum size (140 (W) × 220 (L) × 40 mm (H)) was developed. The developed techniques were used to
retrieve images of fruits and vegetables, taken by the digital camera. The developed technique can retrieve images of
certain fruits, such as an apple, from images of many different fruits and vegetables. It will open up a new area of
retrieval techniques for ambiguous images based on shape, colour and texture information.
We present a new slot-in type of optical correlator that is more compact than the previous types. The correlator can fit
inside the cabinet of commercial personal computers and is fully controllable with windows-based software. The
correlator is a Joint Transform type (JTC) and its optical system fits inside a metal box measuring 140 mm (W) x 220
mm (L) x 40 mm (H). The optical source is a 650-nm-band laser diode of the kind used in DVD systems. A spatial light
modulator and a CMOS camera are installed in the metal box with the passive optical components required for the JTC.
The collimated light from the laser diode is illuminated on the spatial light modulator displaying reference and data to be
examined. The light reflected from the modulator is Fourier-transformed by a lens on the plane of the CMOS camera.
The computer reads the power spectrum recorded by the camera and modulates the spatial light modulator. This process
is repeated. We found that these JTC processes could be performed with the prototype developed in this study.
We propose a new technique for retrieving color information. The color data taken by a digital camera is transferred to
two-dimensional data on the color chart and displayed on a spatial light modulator. This modulation technique is
combined with a retrieval technique using a joint transform correlator. The color data, e.g., photograph of a flower, are
retrieved by this system, and the same color data (photograph) can be perfectly selected from the many reference data.
This technique will open a new area of retrieval techniques for ambiguous images based on shape and color information.
We have studied magneto-optical responses of gold-bismuth-substituted yttrium iron garnet (Au-Bi:YIG) composite films in which Au particles are embedded into Bi:YIG in two different ways. First type were samples in which planar arrays of Au particles were introduced into the middle of Bi:YIG films using a step-by-step sputtering technique. Second type were granular films fabricated using simultaneous co-sputtering of Au and Bi:YIG; in these films Au particles occupy positions inside composite films in a random way. Absorption bands associated with localized surface plasmon resonances (LSPRs) were observed in transmission spectra of films of both types. In the spectral range of LSPRs, samples of Au-array type exhibited larger Faraday rotation angles as compared with that for reference Bi:YIG films of the same thickness. However, given that the volume fraction of Au particles was nearly the same for both types, the
enhancement of Faraday rotation for samples of Au-granular type was insignificantly altered. Experiments showed that of the primary importance is the role of the interfaces between Au particles and Bi:YIG. Theoretical estimations showed that, in samples of
Au-granular type, air shells appeared between Au particles and Bi:YIG during fabrication. In fact, annealing needed for crystallization of Bi:YIG films is always accompanied with an expansion of their thicknesses.
Recently magneto-optic spatial light modulators (MOSLMs) using magnetic garnet materials have advantages of high
switching speed. However, these materials are difficult to be used in short wavelength range, so that it appears huge light
absorption by magneto optic effect of transmittance mode (Faraday effect). This problem can be solved by using the
materials of metal magnetic films for magneto optic effect of reflection mode (Kerr effect). We suggest the new method,
which is the switching of pixels by heating the pixels with semiconductor laser until Curie temperature and changing the
direction of the driving current at the same time, for developing high speed MOSLM in broadband using amorphous
TbFe films. TbFe films were fabricated by RF sputtering using the Tb21Fe79target, and we have confirmed Kerr rotation
(over 0.4 degree from 400nm to 800 in wavelength), the curie temperature (130 degree Celsius), and the switching of
pixels of 16μm × 16µm by heating the pixels with semiconductor laser and controlling magnetization from external bias
magnetic field (15Oe) and driving current (20mA) of coil at 403, 532 and 633nm wavelength.
We report on an analytical study of the photonic band structure of 2D and 3D multi-component photonic crystals. It is found that both types of crystal demonstrate a quasiperiodic resonant behavior of (hkl) photonic stop-bands as a function of the reciprocal lattice vector, providing a selective ON/OFF switching of nonresonant (hkl) stop-bands. Our predictions are compared with the results of conventional numerical studies using the photonic Korringa-Kohn-Rostocker method. Experimental transmission spectra of a-SiO2 synthetic opals show the OFF-switching of the {111} stop-bands at the filler permittivity of ~1.82, the {200} bands at ~1.63, the {220} bands at ~1.93, and the {311} bands at ~1.75. The (222) photonic stop-band, which is due to the second order diffraction from the (111) planes, cannot be switched OFF in a wide range of filler permittivity values, thus indicating a resonant behavior. The experimental data demonstrate an excellent agreement with the theoretical predictions.
We develop a method to study the optical and magneto-optical response of perforated metallic films with magneto-optic
media embedded within their holes. Due to the strong electromagnetic field confinement associated with the excitation
of the transmission resonances appearing in this type of structures and nonreciprocal nature of the magneto-optical
phenomena, strongly enhanced conversion of the polarization state in both reflected (magneto-optical Kerr effect) and
transmitted (magneto-optical Faraday effect) waves was found. Possibility to reach huge rotation angles is demonstrated
by increasing magneto-optic holes filler/background optical contrast, which appears to be responsible for the resonance
quality.
In this work, we investigated the possibility of application of magnetophotonic crystals to the optical magnetic field
sensor. The structure of 1D-MPC was (Ta2O5/SiO2)5/Bi:YIG/ (Ta2O5/SiO2)5 (magnetic material as a defect layer between
two Bragg reflectors) on a fused quarts substrate using RF magnetron sputtering apparatus. We used Bismuth substituted
yttrium iron garnet (Bi:YIG) polycrystal film as a defect layer, because Bi:YIG is well known as the magnetic material
with effective MO properties, even if it is polycrystal. Due to specially designed structure, the localized mode appeared
at the wavelength of 880 nm, which is tunable by the thickness of multi layers or defect layer. At the wavelength of
localized mode, Faraday rotation was shown large enhancement of 1.5°, that is fifty times larger than for single Bi:YIG
polycrystal film of the same thickness.
Optical properties of mesoporous three-dimensional photonic crystals (3D PCs) based on thin opal films were found to be extremely sensitive to a humidity of the surrounding air. It was manifested that the internal structure of a single SiO2 sphere together with the net of voids between them in a thin opal film acts as a sponge for wet steams. Our experimental data have shown that hydrophilic internal structure of a mesoporous film sponges up (and lose) water (dry or wet steams) that influences dielectric permittivity, the latter causes significant changes in transmission spectra. High sensitivity, quick response and possibility of contactless measurements makes sensors based on optical effects in mesoporous PCs to be very promising. It concerns not only humidity sensors, but also sensors of various gases, temperature, deformation and other environmental impacts.
Highly transparent polycrystalline lanthanum-modified lead zirconate titanate (PLZT) thick films were prepared using
aerosol deposition method (ADM) of calcined complex powders. Effects of incident angle of aerosol and particle size as
well as annealing temperature on optical and electro-optic properties of films were investigated. The film with higher
transparency was obtained with smaller particle, because the aggregation frequency of particles in aerosol decreased with
reducing the particle size. The transparency of the films increased with decreasing the incident angle of aerosol. This is
presumably due to the fact that the optimal incident angle of aerosol results in the reduction of impurity and pore, which
makes the film to be denser micro-structurally. The XRD peaks of as-deposed films shifted to lower angle side,
indicating that large compressive stress, which was generated by mechanical collision of particles, acted in the films. But
the stress was eliminated through annealing process. The birefringence change in annealed film increased exponentially
with an applied electrical field to reach 0.0036 at 100kV/cm. To make a multimode waveguide, the PLZT film with 22
μm thick was formed into a silicon groove, which was fabricated through anisotropic wet etching process. The far field
profile of multimode optical wave transmitted through the fabricated PLZT waveguide was successfully observed and
could be controlled with an applied electrical field.
This paper represents fabrication and properties of an improved current-driven 128 by 128 magneto-optic spatial light modulator (MOSLM) consists of arrayed pixels patterned with 14 micrometers square of 16 micrometers pitch. It could be driven successively only drivelines without a bias field by external coil to saturate magnetization. The magnetic pixels were embedded into the nonmagnetic substrate both to avoid magnetic switching error and to make the pixels array surface smooth. The switching field of arrayed pixels was reduced to 145Oe by annealing them to decrease the growth induced magnetic anisotropy. This value was about half of the conventional 128 by 128 MOSLMs. Moreover, copper straight drivelines were used for decreasing electric power consumption and applying a homogeneous magnetic field to the pixel. This drivelines structure enabled to switch the individual pixels reversibly keeping a single domain state, therefore, the successive driving of writing and erasing various checker patterns could be possible without bias field by external coil. The electric power consumption was decreased about 70 %. The switching speed of one pixel was 25 nanoseconds. It is more than a thousand times faster than other types of SLM, for example, 10 to 30 milliseconds for liquid crystal (LC) type, and 10-20 microseconds for micro electro mechanical systems (MEMS) type.
Spatial light modulators (SLMs) are key components of collinear holographic storage. Collinear holography utilizes coaxially aligned information and reference beams which are displayed simultaneously by a same SLM for writing process, and also employs reference beam for retrieving process. We developed magneto-optic spatial light modulators (MOSLMs) which have high-speed switching and applied them to transmission-type collinear holography. In this study, we investigate performance of collinear holography with magneto-optic spatial light modulator. The Bit error rate was 8.9×10-3 for single hologram. To examine the performance of shift-multiplexing, reconstructed image was disappeared after 3 μm shift. MOSLMs is suitable for collinear holography in terms of transfer rate especially.
We present a new method for calculation of optical and magneto-optical properties of three-dimensional magnetophotonic crystal heterostructures, composed from a sequence of homogeneous plates of a magneto-optical material and photonic crystal slabs. The algorithm is based on the layer KKR technique. As examples we consider the Bi:YIG (bismuth-substituted yttrium-iron-garnet) magneto-optical plate sandwiched by photonic crystal slabs consists of (i) simple cubic/face centered cubic lattices of SiO2 spheres in the air; (ii) air spheres in silicon background (inverse opals). The enhanced Faraday rotation appears at the resonant transmission frequency in analogy with one-dimensional structures with magneto-optical microcavity. However, the calculated spectral behavior of the Faraday rotation as well as its dependence on defect thickness is quite different and unusual. For instance, the Faraday rotation angle changes its sign within the photonic band gap that is due to complicated reflection of waves from 3D photonic crystal slabs.
Realization of enhancement of second-harmonic generation (SHG) in
three-dimensional (3D) photonic crystals utilizing nonlinear
diffraction is demonstrated. The samples are composed from
close-packed silicon oxide spheres with diameter of 250 to 300 nm in
each sample forming an ordered fcc opal matrix. The opal voids are
filled by noncentrosymmetric gallium nitride and centrosymmetric
silicon with filling factor close to unit. The photonic band gap
(PBG) is obtained for light reflected from the (111) face and
localized in the spectral region from 800 to 950 nm for different
samples. SHG spectra show pronounced peaks as the fundamental
radiation is tuned across the photonic band gap. The intensity
enhancement in SHG is about 100 and the spectral width of the SHG
resonances is approximately 15 nm. The SHG enhancement is attributed
to combination of linear diffraction of the fundamental radiation
from the (111) opal layers and nonlinear diffraction utilizing the
3D periodicity of the quadratic susceptibility of silicon and
gallium nitride nanocrystals in opal voids. The spectral position of
the SHG peak is slightly red-shifted in comparison with the PBG
center and attributed to condition of the group velocity minima.
We demonstrated a magneto-optic spatial light modulator with one-step pattern formation of iron-garnet films on ion-milled substrates by LPE. The one-step pixel growth is based on the combination of a single-crystal epitaxial film growth (pixel area) by LPE and a impeded film growth (pixel gap area) on a substrate whose surface has been locally damaged and milled by ion bombardment before film deposition. This method overcomes the disadvantages associated with groove etching of the conventional MOSLM. The fabricated prototype MOSLM is switched by applying driving currents of 40 mA for the bottom conductor line and 80 mA for the top conductor line under external bias field of 20 Oe, which is over 2 times smaller than that of the conventional MOSLM. These results strongly suggest that the novel MOSLM can provide higher resolution, simpler fabrication process, more compact systems and lower driving current. Also, the selective-area LPE method offers new possibilities for the fabrication of integrated magneto-optic light switch arrays, magnetic waveguides and similar devices.
This work was aimed at fabrication of a three-dimensional magento-photonic crystal. In our experiments LATEX spheres with diameter of about 200 nm were coated with Fe3O4 fine particle. The diameter of Fe3O4 fine particles is about 30 nm when ration of Fe3+ / Fe2+ (r) = 3% and pH = 8.6. The diameter of these particles decreases about 10 nm by increasing up to r=20% in the same pH region. It was found that a decrease of the coated particles size can be made as low as the size of 5% of LATEX spheres diameter. Therefore, it may use these particles for preparation a three-dimensional magento-dielectric structure.
We demonstrated a flat-surface magneto-optic spatial light modulator (MOSLM) without physically isolated pixels and an external bias coil. The flat-surface MOSLM, which was fabricated by a simple process, was designed as a compact system with a high resolution and very low driving current. Flat-surface pixels for the novel MOSLM were magnetically isolated and produced by the combinatory use of the local annealing effect that reduced magnetization 4πMs of pixel areas and the stress effect that produced sharp variations of magnetic anisotropy in a magnetic garnet film under the edge of a metal layer. The novel MOSLM can provide a higher resolution, a simpler fabrication process, more compact systems and a lower driving current than the conventional MOSLM.
In this paper, results of the first observation of magnetization-induced second-harmonic generation (SHG) in one-dimensional magneto-photonic microcavities are described. Both significant magnetization-induced rotation of second-harmonic wave polarization and magnetization-induced variations of the SHG intensity are detected at the fundamental wavelengths in the vicinity of microcavity mode.
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