Calibration of optical metrology stereophotogrammetric systems is vital to obtain accurate and precise three-dimensional (3-D) measurements. Despite its importance, the work pipeline of intrinsic and extrinsic camera calibration still remains manually laborious with high technical complexity. The use of a multilayer perceptron neural network to calibrate an optical metrology stereophotogrammetric system utilizing a statistical band-limited pattern projection system is demonstrated. Highly accurate, highly precise, and highly dense 3-D surface reconstructions are obtained solely from homologous corresponding pairs without the need for intrinsic and extrinsic camera calibration. Measurement performance in the typical optical metrology sense, where 3-D measurements were evaluated with respect to length and surface gauges, is shown.

This paper presents a pose estimation method for planar mirror based on a one-dimensional (1-D) target. First, a 1-D target is maneuvered in front of a camera so as to allow the camera to capture several images of both the original and virtual feature points on the target. Next, the normal vector of the mirror and the distance between the mirror and the camera are calculated by a closed-form method. Last, a nonlinear optimization is used to refine the closed-form solution by minimizing the reprojection error of reflection projection. Synthetic data and real experiments show that the proposed method is accurate and reliable. The proposed method is simple and flexible. No prior information about the target motion and camera pose is assumed. A minimum of two nonparallel target positions are required. It is suitable for the pose estimation of planar mirrors, especially when they are in fixed positions. We can find the posture of the fixed camera according to the normal vector of the plane mirror.

Optical sectioning through the numerical reconstruction of digital holographic data with low diffraction noise is the key process for understanding the structure of a recorded three-dimensional object. Recently, this has been enabled by compressive holography, by virtue of sparse signal processing. However, interpretation of the object signal domain has been limited to predefined domains, such as spatial, discrete cosine transform, and wavelet transform domains. We propose a reconstruction technique of compressive Fresnel holographic data using an overcomplete dictionary learned from natural images to enhance the axial resolution of the sectional images. The redundant (overcomplete) dictionary gives sparser and more flexible solutions for representing the two-dimensional images compared to predefined transforms. We provide simulation results to verify the feasibility of our proposed method.

When the interval between transmitted pulses is shorter than the time of flight, it is not straightforward for a lidar to determine the distance uniquely. We present a method that uses varying pulse intervals, constructs a set of tentative point positions for each received pulse, and exploits the clustering of such tentative points to determine the correct distance with high probability. The clustering of true points also helps suppress noise pulses, even in a regime where the number of noise pulses is far greater than the number of true return pulses. It is then possible to use a detection threshold close to the noise level.

A visual localization approach for unmanned aerial vehicles (UAVs) based on the hybrid real-time stereo visual odometry (VO) is presented. The hybrid VO initializes the semidirect visual odometry (SVO) with depth obtained from the stereo camera, which runs with the monocular scheme at 30 Hz. Meanwhile, a feature-based stereo VO runs in a parallel thread to improve the reliability. Considering the robustness of the feature-based VO, we not only are able to estimate the pose of the UAV with the same rate of the incoming images but also to recover the pose of the UAV when the SVO fails. We demonstrate the accuracy and the reliability of the hybrid VO based on a public benchmark dataset and a dataset recorded on our experimental platform. In addition, the autonomous hovering experiment verifies that the estimated result is fast and accurate enough to control the position of the UAV.

Multitarget tracking in video surveillance is challenging because the appearance features of the target are often unreliable in complicated scenes. To solve the problem, we propose a multitarget tracking method using multifeature model with acceleration feature. First, an acceleration feature descriptor is derived from the histograms of the optical flow features according to the background difference. Our approach filters and normalizes the descriptors of consecutive frames to establish acceleration feature models. Then, the multifeature models of target templates are initialized by combining acceleration and multiple spatial feature models. Second, we implement data association based on the tracklet confidence by integrating the acceleration and multiple spatial feature affinities. As a result, the optimal associated pairs between target tracklets and detections are solved by the Hungarian algorithm. Finally, our tracking system updates the multifeature models of target templates online depending on the reliability of the tracklets, and the trajectories of multiple targets are output. Experiments conducted on the challenging multiple object tracking benchmark confirm the effectiveness and superiority of the proposed method.

An analysis is presented of the error introduced into estimates of avalanche photodiode (APD) laser-rangefinder performance by assuming Gaussian distribution of the APD multiplication gain. The amplitude of current pulses emitted by an APD obeys the McIntyre distribution, the tails of which diverge from the Gaussian distribution having the same mean and variance. Because extinction of false alarms requires setting a discrimination threshold far into the tail of an analog photoreceiver’s output distribution, the threshold level required to achieve a specified false alarm rate (FAR) using an APD-based photoreceiver is often not accurately predicted by the standard FAR model of Rice. Characteristics of APD-based photoreceivers are calculated using the McIntyre distribution and are compared with characteristics calculated using the Gaussian approximation.

Three-phase segmentation of solid oxide fuel cell (SOFC) anode image is essential for its microstructure quantitative analysis. A quantum-inspired mixture clustering model is developed for Ni/YSZ anode optical microscopy (OM) images. The proposed mixture clustering model focuses on combining Markov random field (MRF)-based fuzzy logic model with Gaussian mixture model (GMM). In the premise part of fuzzy if-then rules, the clique potential MRF function is defined by multiplication of both prior distributions and fuzzy membership functions with a quantum-inspired adaptive fuzzy degree, which takes prior statistics properties and spatial contextual information of SOFC anode OM image into consideration. In addition, GMM is introduced into the consequent part to design a negative log-prior function as the pixel distance metric. The proposed method has been compared to other state-of-the-art segmentation algorithms on both simulated images and real SOFC anode OM images. The experimental results demonstrate that the proposed method is able to achieve a higher segmentation accuracy with a faster convergence speed, which lays firm foundation for microstructural parameters extraction from SOFC electrodes image datasets.

This research presents an algorithm for three-dimensional (3-D) pose tracking of a rigid object by processing sequences of monocular images. The pose trajectory of the object is estimated by performing linear correlation between the current scene and a filter bank constructed from different views of a 3-D model of the target, which are created synthetically with computer graphics. The pose tracking is guided by particle filters that dynamically adapt the filter bank by taking into account the kinematics of the target in the scene. Experimental results obtained with the proposed algorithm in processing synthetic and real images are presented and discussed. These results show that the proposed algorithm achieves a higher accuracy of pose tracking in terms of objective metrics, in comparison with that of existing similar algorithms.

Three-dimensional (3-D) laser beam steering of focal position has been demonstrated using a single optical device—a DMD micromirror array. Laser beam focus position is controlled using dynamically adjustable zone plates. These zone plates take the form of elliptical Fresnel zone plates or other variations such as binary Gabor zone plates. Active beam pointing and control can be realized without the need for a pair of galvanometer mirrors and a focusing lens. Focusing efficiencies into an off-axis diffraction order of a few percent are typically seen and continuity between neighboring orders increases the effective field of regard. Writing multiple zone plate patterns to the DMD enables multiple focused spots to be generated and controlled independently.

In digital holography, the reconstructed resolution is generally limited by the size of the numerical aperture. For a lens-free imaging configuration, the high-frequency information is lost due to the finite size of the recorded area. It is challenging to obtain an enhanced-resolution recovery with the finite-recorded hologram. Here, we propose an algorithm to enhance the reconstructed resolution by utilizing sparse prior of the image. We combine the sparse regularization term with the extrapolation of the recorded area based on the inverse problem approach. For regularization, the ℓ₀-norm is utilized to promote the sparsity of the solution during the iterative process. An iterative optimization algorithm is developed to solve the nonconvex resolution enhancement problem, which is implemented by substituting the primal–dual saddle-point problem for the primal problem. Our method can circumvent the limitation of the recorded area and produce enhanced-resolution recovery by employing the sparsity of the object distribution. Both the simulation and experiment indicate that the proposed algorithm can achieve the superior enhancement for reconstructed resolution with a single captured hologram in a digital in-line holography.

Ghost imaging is an indirect system that allows the imaging of an object without directly seeing the object. The speckle pattern that contains the information about light and objects has increasingly become a popular topic in pseudothermal light ghost imaging. However, existing research still has encountered problems of poor imaging quality and slow sampling speeds. We propose a ghost imaging method based on N-order speckle patterns to recover the object (NSGI). The N-order speckle patterns combine N independent laser speckles individually produced by passing an expanded and collimated He–Ne laser through a digital micromirror device (DMD). The sampling frequency can be improved by controlling the trigger signals of different DMDs. The results of the simulation and experiment have verified that our method can increase sampling speed and reconstruction accuracy. In addition, NSGI can be applied to more applications by designing multiple independent speckles with different properties.

X-ray framing camera (XFC) is usually used as the principal diagnostic tool in inertial confinement fusion research. The methods on how to precisely calibrate the temporal resolution are important topics for XFC with several picoseconds gate time. A method to measure the temporal resolution of XFCs is proposed based on a high-power subpicosecond ultraviolet laser facility called LLG-ultimate. In our method, series of duraluminium alloy stepped reflective surfaces are used to separate the incident laser beam into sequentially delayed beams with equal size, spacing, and time interval. The temporal resolution of XFC can be measured if the sequentially delayed beams irradiate a gold photocathode microstrip line while the high-voltage pulse transferring along the same area simultaneously. A Fabry–Perot etalon is placed in the light path, improving the probability of synchronization of the voltage pulse and laser pulse. The accuracy of this measurement method can be very high by reducing the time interval of the sequentially delayed beams.

This paper presents the use of the high-speed digital image correlation (DIC) method for measurement of the head injury of a pedestrian in a vehicle–pedestrian collision experiment. Two simultaneous high-speed cameras captured the images of the impact process between the head-simulator and the car hood. The DIC method can achieve comprehensive analysis of the impact and help to reconstruct the impact process, from which not only the velocity, acceleration of the headform impactor, and the head injury criterion (HIC) but also the angular velocity and acceleration can be calculated. The possibility of using DIC to calculate of the neck injury criterion (NIC) is also discussed in this paper. Furthermore, the quantitative calculation of the full-field deformation of the car hood during the collision can also be achieved with the DIC method, which is of great practical value in optimizing automobile design and collision protection. A vehicle–pedestrian collision experiment is carried out, and the comprehensive results show that the DIC method can obtain accurate and comprehensive data in the calculation of human and vehicle collision.

High-power laser devices have stringent requirements for the surface accuracy of optical elements. Continuous polishing is an effective technique for polishing high-precision optical elements. To overcome the problem of poor real-time capability and low accuracy in traditional surface shape monitoring and controlling methods used in continuous polishing, an online monitoring device is developed to monitor the surface shape of the polishing pad. The experimental results of the online measurement are highly consistent with the offline results obtained using an interferometer. The correctness and feasibility of the online monitoring scheme are well validated. Based on the online monitoring device for the surface shape of the polishing pad, we propose a method of automatic control for the surface shape of the polishing pad. This method maintains the flatness of the polishing pad to 0.05λ (λ = 632.8 nm), peak to valley, as measured on a 100-mm monitoring element through computer control.

To achieve nonscanning three-dimensional measurement of microstructures, the optically sectioning mechanism has been used based on the structured illumination microscopy. The key point is to implement nonscanning measurement within a limited axial range according to the measured one-sided linear response curve. One-dimensional transmission grating pattern was projected onto the sample, and optically sectioned images were extracted from three-step phase-shifting manipulation. Compared with the basic and differential confocal microscopy, the described method does not need time-consuming axial scanning, so it greatly improves the measurement efficiency. The results show that the described method is useful in the fields of micromechanics, microelectronics, and biomedicine.

Interferometers using computer-generated holograms (CGHs) have become the industry standard to accurately measure aspheric optics. The CGH is a diffractive optical element that can create a phase or amplitude distribution and can be manufactured with low uncertainty using modern lithographic techniques. However, these CGHs have conventionally been used with visible light and piezo-shifting interferometers. Testing the performance of transmissive optics in the infrared requires infrared CGHs and an infrared interferometer. Such an instrument is used in this investigation, which introduces its phase shift via wavelength-tuning. A procedure on how to design and manufacture infrared CGHs and how these were successfully used to model and measure the Wide-Field Infrared Survey Telescope grism elements is provided. Additionally, the paper provides a parametric model, simulation results, and calculations of the errors and measurements that come about when interferometers introduce a phase variation via wavelength-tuning interferometry to measure precision aspheres.

An approach for wavefront reconstruction based on a defocused Shark–Hartmann sensor is proposed. In this approach, not only the first-order origin moment (local slope of the input wavefront) but also the second-order central moment (local curvature of the input wavefront) of each spot in the intensity pattern is used to reconstruct the input wavefront. By introducing the second-order moment, an improvement of reconstruction accuracy can be obtained. As the ambiguity of the sense of the local curvature of the input wavefront exists in the scheme of the conventional Shack–Hartmann sensor in focus, a defocusing scheme is adopted to solve this problem. Based on modal and zonal methods, respectively, the corresponding algorithms are invoked to reconstruct the wavefront from the map consisted of both local slopes and curvatures. Numerical experiments show that the reconstructed wavefront by the proposed method is more accurate, in comparison to the result by the conventional method. It should be mentioned that the defocused sensor used in the proposed method sacrifices, to some extent, the dynamic range of measurement.

This paper proposes and investigates a partial discharge (PD) detector based on fiber Bragg grating (FBG) sensor and a mandrel to detect and localize PD in power transformers. An identification of PD in the early stages is important, so using high-resolution sensor is considerable. A Teflon hollow mandrel with attached FBG is chosen as the inner transformer PD detector. The design of the sensor in terms of materials, dimensions, and the shape is chosen; it receives signal strength according to the obtained distance and angle. Standard deviation of angle data is <0.4  mV and as the distance increases, the received signal strength decreases exponentially and oscillatory. Simulation results verify the performance of the proposed sensor in the detection of the transformer PD signals. The proposed sensor is experimentally tested. It succeeded in detecting PD, and can simultaneously detect four frequencies of acoustic signal in the range of 14 to 350 kHz, which is superior to similar sensors.

A method utilizing matrix analysis has been presented for a full-area three-flat test. With the aid of the Moore–Penrose pseudoinverse of a circulant matrix, a set of closed mathematical formulas has been derived to obtain the absolute profiles of samples. According to the simulation results, the matrix analysis method shows better performances for determining the absolute profiles and suppressing the decorrelation residuals of the reconstructed wavefronts, compared to the iterative method. Three optical flats with 135-mm apertures are measured. The results obtained with the new method agree well with those obtained with the iterative algorithm and the classical three-flat test. Furthermore, the relationship between the decorrelation residual and the wavefront error introduced in the rotation measurement has been studied. Theoretical and experimental results show that the odd-symmetric component contributes significantly to the decorrelation residual.

Stress-birefringence measurement is critical in optical glass materials. A laser self-mixing interference (SMI) stress measurement system with a measuring range of 1 deg to 179 deg is presented. The light source of the system is a He-Ne laser with a variable frequency difference. Birefringent external cavity SMI experiments are conducted with the laser with different frequency differences. Experimental results show that a large frequency difference decreases the cross-saturation effect between the two laser eigenstates, and alternate oscillations are more likely to occur, which directly improves the sensitivity and expands the measuring range of the system. A piece of neodymium glass is tested with the system and the results are given, proving that the large frequency difference laser SMI system provides a simple, low-cost, and high-sensitivity stress measurement method.

In our earlier work, we introduced and demonstrated continuous wave frequency modulated differential optical feedback to measure low-frequency vibrations with displacements lower than half of emission wavelength of the laser. Using modulated optical feedback interferometry on perturbations whose amplitude was smaller than half the emission wavelength of the laser, the proposed sensor-enabled nanometric scale amplitude measurements from the shift in fringes that appear in a vibrating target by comparing them with the fringes on the stationary target. We extend the application of the technique to noncontact measurement of surface perturbations generated by acoustic beams. First, the displacement of the acoustically perturbed membrane of the transducer at a frequency of 26 kHz with an amplitude of 101 nm (λ  /  10) is performed using a single laser diode in a point-and-measure fashion. Once the acoustic waveform has been characterized, the instantaneous surface displacement of a remote aluminum plate due to acoustic pressure is measured using the same setup, yielding a value of 75 nm. As a consequence, an application of a very cost-effective, noncontact, and high accuracy sensor based on the laser diode under optical feedback has been presented.

Color perception of an object is tremendously influenced by the spectral power distribution (SPD) of a light source. Therefore, it is of great significance to seek for an optimal SPD to enhance the color contrast of a biological specimen in medical lighting. Meanwhile, considering that color rendering property and illuminance are of importance to lighting, with a multichannel LED light source and a differential evolution algorithm dealing with the constraints of color rendering and illuminance, a contrast enhancement method based on maximizing CIEDE2000 color difference ( ΔE00*) was proposed in this study. An illuminance level of 500 lx was first verified as the desired illuminance. Afterward, the color contrasts of six groups of color patches were optimized under four different constraints of the Commission Internationale de l’Eclairage (CIE) general color rendering index (R_a), i.e., R_a  ≥  0, R_a  ≥  60, R_a  ≥  80, and R_a  ≥  90, manifesting their significant color contrast enhancement under the optimized light sources compared with those under the simulated CIE A, D50, D65, and D75 light sources. Further, two biological samples, pork tissues and porcine heart, were optimized under the four constraints of R_a. The results show that even in the case of R_a  ≥  90, the optimized ΔE00* values for the two specimens are, respectively, 4.13 and 3.20 higher than those under the D75 light source. More importantly, the developed method also provides a flexible lighting solution to color contrast enhancement.

For large space telescopes, the design of lightweight primary mirrors with an acceptable level of optical performance is a challenge. A parametric optimization method based on topology optimization of the basic configuration of the mirror is proposed. A finite-element model of the mirror is generated with linear shell elements, and the optimal distribution of the material is obtained using the continuum topology optimization technique. The lightweight ribs are grouped according to the results of topology optimization results. The design of experiment method is used to pick out the key factors for parametric optimization. The RMS value of the surface shape error of the mirror and the total mass of the mirror are treated as the objective merit functions, and the first-order natural frequency of the mirror is taken as a constraint for parametric optimization. Results show that the local stiffness of the mirror is significantly affected by the thicknesses of the ribs at the corresponding positions. The optimum mirror design obtained using our optimization method is compared with the initial design, and the comparison shows superior optical performance for the optimized mirror.

We have developed an 8K4K liquid-crystal display (LCD) with diagonal size of 55 inch with the backplane based on an amorphous silicon (a-Si) technology. The 8K4K-LCD has high frame frequency at 120 Hz, which is enabled by a unique technology to compensate the charging voltage of pixels. The achievement of a high resolution of 8K4K including high frame frequency of 120 Hz with a-Si backplanes is ground-breaking for LCDs. Furthermore, a backlight system with laser diode as light source expands the color gamut dramatically. This backlight system enables covering 99% of color space recommended in BT.2020. What is more, the 8K4K-LCD has evolved into a three-dimensional (3-D) display device by attaching a 3-D polarizing film. The vertical viewing angle of the 8K-3D LCD prototype is 8.6 deg at its optimal viewing position set to 1.2 m.

A silicon photonic crystal (PhC)-based structure is proposed to efficiently couple power from two different wavelengths, targeted to the application of an integrable Raman amplifier. The coupler uses two asymmetrical PhC waveguides as input ports which are joined together and the coupled power is directed to a slotted photonic crystal waveguide-based output port. Coupling efficiency and the other performance metrics are evaluated using a three-dimensional full-vector finite-difference time domain simulation method, which is tested for accuracy using some existing experimental structures and corresponding results. The heuristic approach has been adopted to optimize the design for maximizing the coupling efficiency. Dependence of the coupling performance on different design parameters has also been investigated. Simulations exhibit ∼3-dB coupling losses for both arms in a small footprint as small as ∼54  μm².

The use of visible light communication (VLC) in vehicular communication systems for vehicle safety applications is proposed. The system aims to ensure the communication between a LED-based VLC emitter and an on-vehicle VLC receiver. A traffic scenario is established. Vehicle-to-vehicle (V2V) and infrastructure-to-vehicle (I2V) communications are analyzed. For the V2V communication study, the emitter was developed based on the vehicle headlights, whereas for the study of I2V communication system, the emitter was built based on streetlights. The VLC receiver is based on amorphous SiC technology and enhances the conditioning of the signal enabling to decode the transmitted information. Receivers are located at the rooftop of the vehicle, for I2V communications, and at the tails for V2V reception. Clusters of emitters, in a square topology, are used in the I2V transmission. The information and the ID code of each emitter in the network are sent simultaneously by modulating the individual chips of the trichromatic white LED. Free space is the transmission medium. An on–off code is used to transmit data. An algorithm to decode the information at the receivers is set. The proposed system was tested. The experimental results confirmed that the proposed cooperative VLC architecture is suitable for the intended applications.

This paper investigates the transmission performance of a 1.55-Tb/s Nyquist-wavelength division multiplexing superchannel along with a mixed line rate approach using 4  ×  111  Gb  /  s polarization-multiplexed quadrature phase shift keying (PM-QPSK) and 5  ×  222  Gb  /  s polarization-multiplexed quadrature amplitude modulation (PM-16QAM) formats. The system transmission performance with acceptable bit error rate of 4  ×  10^−  3 is analyzed over standard single mode fiber (SSMF), large effective area fiber (LEAF), and pure silica core fiber (PSCF). It is observed that SSMF increases 45% reach over LEAF, whereas PSCF increases 66% to 84% reach over LEAF for 4.5 b/s/Hz spectral efficiency of the system. Also, spectral efficiency × distance product of 24,750 and 10,350 b/s/Hz.km are obtained for PM-QPSK and PM-16QAM, respectively, which is, to the best of our knowledge, better in comparison with the other existing literatures for single core channel investigations.

The thermal stability of optical antennas is a key parameter determining the performance of satellite optical communication links. The effects of uniform temperature changes on the performance of a Cassegrain optical antenna are discussed. In addition, a simple theoretical model is proposed to describe the defocusing distance and wavefront aberration (power) as a function of temperature. Through the theoretical model, the thermal stability can be quickly assessed in the optical design stage. The alignment data and thermal experimental results are consistent with the theoretical model.

Polymer flow during wire coating in a pressure type coating die has been simulated under nonisothermal conditions. The flow is dependent on the wire velocity, geometry of the die, and the viscosity of the polymer. The constitutive equation of an Oldroyd 8-constant fluid is used to characterize the rheology of the polymer melt. The equation describing the flow of polymer melt inside the die is solved (i) analytically by applying optimal homotopy asymptotic method and (ii) numerically by shooting method with Runge–Kutta–Fehlberg algorithm. The convergence of the series solution is established. The effect of physical characteristics of the problem has been discussed in detail through graphs by assigning numerical values for several parameters of interest. At the end, this study is also compared with the published work as a particular case and good agreement is found.

A method to improve the refractive index (RI) and temperature sensitivities of optical fiber based on surface plasmon resonance (SPR) sensors is proposed and experimentally demonstrated. It is realized by using a precision femtosecond laser system to manufacture microstructures on a heterocore optical fiber structure (multimode single-mode multimode fiber, MSM). The microstructured MSM structure fiber-optic sensors were coated with 60-nm gold (Au) film to test and verify RI sensing, obtaining an enhancement of the maximum sensitivity range from 2845.18 to 3313.15 nm/RIU. The fabricated sensors were additionally coated with a layer of polydimethylsiloxane, which has a high negative thermos-optic coefficient, to conduct a series of temperature sensing experiments. Experimental results showed that the maximum sensitivity increased from 1.1998 to 1.5646 nm/°C. Compared with nonmicrostructured sensors, the RI and temperature sensitivity of the proposed sensor has increased 16.4% and 30.2%, respectively. The simply fabricated, low-cost, and high-sensitivity SPR sensor has promising applications in many areas, especially in the biochemical field.

The optical ground station (OGS), installed in the Teide Observatory since 1995, was built as part of ESA efforts in the research field of satellite optical communications to test laser telecommunication terminals on board of satellites in Low Earth Orbit and Geostationary Orbit. As far as one side of the link is settled on the Earth, the laser beam (either on the uplink or on the downlink) has to bear with the atmospheric turbulence. Within the framework of designing an adaptive optics system to improve the performance of the free-space optical communications at the OGS, turbulence conditions regarding uplink and downlink have been simulated within the object-oriented matlab adaptive optics toolbox as well as the possible utilization of a laser guide star to measure the wavefront in this context to cope with the angular difference in uplink and downlink beams due to the point-ahead angle required for the uplink. Simulations have been carried out by reducing available atmospheric profiles regarding both night-time and day-time measurements and by having into account possible seasonal changes. An AO proposal to reduce atmospheric aberrations and, therefore, ameliorate FSO links performance is presented and analyzed in this paper.

A simple and flexible photonic on–off keying (OOK) modulated impulse radio ultra-wideband (UWB) over fiber communication system is proposed and experimentally demonstrated. By introducing a Gaussian signal to the phase modulator, the UWB monocycle pulse is achieved at the output port of a delay interferometer. The UWB doublet pulse is also successfully obtained at the output port of a semiconductor optical amplifier with the injection of the positive monocycle. Only one laser source is introduced in the architecture to guarantee satisfactory dispersion tolerance over a 60-km optical fiber link for UWB OOK sequence, which has potential applications in future high-speed UWB radio over optical fiber access networks.

Flexible Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cells are fabricated on titanium substrate by magnetron sputtering with a composition gradient precursor followed by selenization. By varying polishing time with diluted HNO3 and HF from 0 to 90 s, an atomic force microscope shows that the substrate with the minimal surface roughness of 8.6 nm is obtained with the polishing time of 60 s. X-ray diffraction and Raman spectroscopy reveal a highly crystalline structure for the prepared CZTSSe thin films. The gradual grown up grain size of CZTSSe thin film is observed with the increasing polishing time of the substrate. Compared with the CZTSSe solar cells on untreated titanium substrates, a maximum power conversion efficiency enhancement of 56% is achieved for solar cells on polished substrates, which can be attributed to the reduction of recombination at the interface and isolated defects in devices. External quantum efficiency curves show an enhancement in the visible and near-infrared region after optimizing substrate roughness. On the basis of Ti substrate with a minimum roughness, the percentage reduction of efficiency is found to exhibit the minimum value of 5% after bending for five times.

A flexible optical filter based on tunable arrayed waveguide grating (AWG) with triangular-like model electrodes is designed on lithium niobate-on-insulator. Using the electro-optic effect of lithium niobate, the 10^−  3 increase of the waveguides refractive index could be achieved with a 4.348-V effective external voltage. The tunable range of the central wavelength of AWG can reach 3.8 nm and the 3-dB bandwidth is about 0.43 nm.

The large majority of surface plasmon resonance (SPR)-based devices use noble metals, namely gold or silver, in their manufacturing process. These metals present low resistivity, which leads to low optical losses in the visible and near-infrared spectrum ranges. Gold shows high environmental stability, which is essential for long-term operation, and the lower stability of silver can be overcome through the deposition of an alumina layer, for instance. However, their high cost is a limiting factor if the intended target is large-scale manufacturing. This work considers a cost-effective approach through the selection of aluminum as the plasmonic material and hydrogenated amorphous silicon instead of its crystalline counterpart. This SPR structure relies on Fano resonance to improve its response to refractive index deviations of the surrounding environment. Fano resonance is highly sensitive to slight changes of the medium, hence the reason we incorporated this interference phenomenon in the proposed sensing structure. We report the results obtained when conducting finite-difference time-domain algorithm-based simulations on this metal–dielectric–metal structure when the active metal is aluminum, gold, and silver. Then, we evaluate their sensitivity, detection accuracy, and resolution. The obtained results for our proposed sensing structure show good linearity and similar parameter performance as the ones obtained when using gold or silver as plasmonic materials.

Three periodic structures based on arrays of graphene-like nanocluster have been proposed and their plasmonic response has been investigated. In the first step, plasmonic response of each periodic structure has been investigated using the hybridization diagram for a proposed single unit cell. In the second step, according to obtained results, appropriate applications for each structure have been introduced. The study is divided into three sections. In the first section, we have considered a periodic array of triangular-shaped nanoparticles to form a graphene-like nanocluster. This configuration shows considerable capabilities to act as a nanoscale waveguide. Alternatively, in the second section, we have replaced triangular nanoparticles with nanospheres. Results of this configuration show considerable enhancements in optical forces and hence, represent it as an acceptable candidate for tweezing and optical manipulations. Finally, we have replaced nanospheres with ring nanoparticles in each node of such a similar nanocluster. This change leads to create states of plasmonic resonances in spectral response, which is sensitive to surrounding medium and can be used as a sensing tool to detect medium perturbations.

In order to realize the application of active surface filtering technology in an optical window, an optically controlled active surface filtering technology is proposed. Photoelectrically conductive thin-film photovoltaic effect is used to control the dimensional change of the metal frequency-selective surface (FSS), thereby achieving active control of surface filtering. Starting from the theory, the principle of active surface filtering technology is described. CST software is used to simulate the FSS characteristics of two types of metal FSSs, “cross” bandpass type and “Jerusalem” band-stop type, under light irradiation conditions. The results show that the filter center frequency is changed from 23 and 13 GHz to 27.6 and 9.8 GHz, respectively, with the change of the structure size. In this experiment, the cross bandpass type and Jerusalem band-stop type optically controlled active FSS are, respectively, fabricated by coating, etching, and electron beam evaporation techniques. With annealing temperature of 750°C and the annealing time of 300 s, it gets the best optoelectronic performance. The experimental results are that the sensitive wavelength of photoconductive thin film is 0.6  μm and the optimal illumination power is 150  mW  /  cm². The sample filter center frequency is changed from 23.8 and 13.5 GHz to 28 and 10.5 GHz, respectively, which is basically consistent with the simulation results. This paper concludes that the use of light control can realize active control of surface filtering.