Conventional energy sources are polluting and limited, and so it is essential to use sources that are less aggressive with the environment. This premise is being transversely implemented in the field of lighting but in response to varied and sometimes contradictory interests. The development of lighting devices based on solar radiation, or daylighting, is an indispensable objective, as is the use of artificial lighting sources that respect the environment. We present the main aspects of important technologies studied for the different fields of lighting, such as optical systems, design techniques, and lighting elements—light guides and those encompassed within nonimaging optics, as well as their implementation and application in various areas such as office lighting, libraries, and museums. We show that an efficient energy strategy in the design of a lighting system not only saves energy and is economic but also produces beneficial and important effects in other nonmaterial aspects of human life, such as well-being, productivity, and heritage conservation.

Long exposure time is one of the major limitations in x-ray phase-contrast imaging (XPCI). Therefore, we demonstrate a promising alternative method for grating-based XPCI coupled with cascaded Talbot–Lau interferometers (TLIs). A Fourier analysis of the moiré fringe patterns generated by the interferometers was used to obtain the multicontrast images (such as absorption, differential phase-contrast, and normalized visibility-contrast images) with a single exposure. The cascaded configuration with TLI and inverse TLI using large-period absorption gratings was established to verify the effectiveness of the algorithm and three multicontrast images of a polytetrafluoroethylene (PTFE) tube were obtained experimentally. The groove structures in the PTFE can be clearly identified in the differential phase-contrast image. This method shows potential for application of cascaded TLI in medical imaging.

The proposed idea is concerned with the investigation of the probability of subatomic quantum communication between chemical substances by use of “interferometric quantum eraser” pattern analysis, which would be the first step toward the further comprehensive study of similar natural communications between the medications and diseased organic tissues. The hypothesis is based on the idea that subatomic particles, such as photons, attempt to access or gain complementary information causing their “wave–particle duality” shifting, which is used to observe their time-sequenced activities. Such information would probably be provided by subatomic quantum communication action demonstrated between the substances in a chemical reaction. Similarly, the medications may have curing effects on a diseased organic tissue after such “natural” communication by which complementary information is transferred from the subatomic properties of a chemical substance to the diseased organic tissue at the same level for the treatment.

Correlation detection can be used to extract weak signals such as those weakened by noise and attenuation. However, complex background noise contains both white and colored noise. The white noise is independent in the time domain, whereas the colored noise has a certain dependency, and the correlation detection algorithm cannot extract useful signals from the background mixed with colored noise. An improved correlation detection algorithm for whitening colored noise is discussed. Simulation experiments show that for laser signal amplitude similar to the noise amplitude, the correlation detection algorithm can extract the pulse signal, and the white noise background has a significantly improved signal-to-noise ratio of 2.3 times higher than the colored noise background. The experiment also proves that the whitening algorithm discussed can extract weak laser signals very well.

Signal interference between two light detection and ranging (lidar) scanners can occur when the transmitted laser energy from one lidar is coupled into a second lidar either by scattering or direct transmission. By ray tracing lidar transmission paths, it is shown that signal interference can be modeled with the coincidence of intersections between two lidars’ optical axes and a scattering target or medium. A geometric analysis of intersecting transmission paths is presented for circularly scanning lidars from which theoretical interference risks between two lidars may be deduced. Using the geometric rules proposed here for interference, a Monte Carlo simulation is presented that models interference risks and occurrences. This geometric approximation simplifies analysis by ignoring radiometry for scanners within proximity to one another. Simulation results are used to introduce the concept of intersection point density from which one may assess areas of greatest interference risk for two-lidar, in-plane scanning lidar configurations. It is shown from the intersection point density that the risk for signal interference between two lidars exponentially increases as targets are located closer to and between the two scanners. Simulation results are compared to previously published experimental observations of interference to demonstrate the theory’s potential for interference modeling.

Recent developments in the areas of image processing have guided a new paradigm for research work in communication of images over the internet. Hence, secure storage and retrieval of digital images is a demanding task for future communication services. A scheme to securely store and encrypt multiple images using sinusoidal phase grating is highlighted. In the proposed scheme, images are modulated using different spatial frequencies and orientation angles. In addition, images have been encrypted using random phase mask after filtering. In order to avoid any human intervention in the system, an intensity graph is plotted to retrieve the images by applying inverse Fourier transform. Using this method, it is possible to independently store, encrypt, and retrieve multiple images due to absence of aliasing problem.

Infrared target acquisition models are used by the military analysis, acquisition, and testing community for sensor design, trade studies, and field performance prediction. We analyze the results of an identification field test, a laboratory perception test on imagery collected during the field identification test, and a perception test using the imagery collected during the field identification test with synthetically added vibration profiles. The purpose of the experiments is to validate model performance predictions in the field, perception laboratory, and to improve model performance predictions of an imaging sensor in the presence of a time varying vibration profile using the night vision integrated performance model (NV-IPM). The results of the observer responses to the image stimuli are analyzed using a mixed effects model at the level of the individual response to derive standard error estimates for the observer responses. The NV-IPM model of the imaging system is derived from field measurements. The field measurements are input into NV-IPM’s new simplified input interface. Results of the observer responses are compared to the NV-IPM model output. Finally, and in a similar fashion, the results of the synthetically added vibration profile experiment are analyzed and a discussion follows on modeling a system that has a time varying vibration component.

Key-cap flatness detection after assembly is one of the basic quality control (QC) indexes in computer keyboard manufacturing. A modified machine vision system based on linear structured light imaging for measuring the key-cap flatness is proposed for keyboard QC automation. After a brief introduction of the system design and principle, the pipeline of light stripe image processing, especially the removal of printed letter interference, is studied. First, the staggered reprojection of dense multiline fringes is presented using the pattern editability of the digital light processing projector to replace the conventional three-dimensional (3-D) sensor mechanical scanning and avoid the movement and cumulative error. Second, an adaptive direction operator based on a Hough transform voting is proposed. This operator is used for directional morphological filtering to remove letter noise and solve the issue of printed letter interference on the key-cap surface, thus improving the accuracy and stability of stripe centerline extraction. Finally, the nonlinear least square method is used to fit the 3-D surface of the key-cap and evaluate its flatness efficiently based on the discrete globally distributed 3-D point cloud data. The experimental result demonstrates that the proposed machine vision system can quickly detect keyboard key-cap flatness and shows superior performance to that of the previous work.

An optically multiplexed image camera often requires a photodetector for image sensing in conjunction with an optical multiplexer, such as a digital micromirror device or an amplitude spatial light modulator. For this type of camera, the advantages of using one photodetector, unfortunately, can be outrun by the fairly large acquisition time, consumed in the image multiplexing process. Therefore, we propose a solution to efficiently improve the image acquisition time span and to relax the computational burden in the reconstruction process. Our camera design incorporates a reflection optical multiplexer, for image encoding, in conjunction with multiple photodetectors. The working principle relies on sequential image encoding using multiple low-resolution sets of binary masks, applied synchronously. The reconstructed data sets form the segments of the final image, which are stitched together with dark boundary pixels.

The Physikalisch-Technische Bundesanstalt has developed a reference setup for measuring the modulation transfer function (MTF) of camera lenses with the goal of reaching an expanded measurement uncertainty of 0.01 (coverage probability of 95%) for various measurement configurations. We present optomechanical simulations of the setup behavior, which are used to investigate the influence of the combined mechanical misalignments on the MTF depending on the lens under test. The investigations are carried out as part of Monte Carlo studies for different sample lenses and field heights considering the correlations between the effects of different positioning errors on the MTF measured. The results of the sensitivity analyses have allowed appropriate alignment strategies to be identified that significantly reduce the uncertainty contribution of the positioning errors. By implementing these strategies, the target measurement uncertainty can be achieved for most of the desired measurement configurations. In addition, the comparison of three different sample lenses shows that the MTF sensitivity to misalignments strongly depends on the characteristics of the lens to be measured.

A real-time computer-generated moiré profilometry (CGMP) with adaptive filtering algorithm is proposed. In CGMP proposed previously, only one static sinusoidal grating needs to be projected onto the measured object and only one deformed pattern caused by the object needs to be captured, which is ideal for real-time three-dimensional (3-D) measurement. By means of generating moiré fringes between the captured deformed pattern and the prestored fringe patterns on the reference plane via computer, the 3-D shape of the measured object can be reconstructed successfully. In phase calculating, this method needs to extract the DC component by filtering. If filtering operation required manual intervention each time, its real-time measuring feature may be limited. For this, an adaptive filtering algorithm based on the maximum fundamental frequency component proportion evaluation function is proposed. It can automatically retrieve an object’s phase information according to the Fourier spectrum distributions of different measured objects without any manual intervention. Experimental results demonstrate the feasibility and validity of the real-time 3-D measuring application.

Aiming at improving signal-to-noise ratio (SNR) and system performance for a Brillouin optical time-domain reflectometer (BOTDR) based on self-heterodyne detection of Rayleigh and Brillouin scattering lights, an approach assisted by modulating probe light and shift-averaging laser frequency, is proposed and demonstrated experimentally. The principles of modulating multifrequency probe light and shift-averaging laser frequency are analyzed theoretically, which are able to increase the signal intensity and reduce the coherent Rayleigh noise, respectively. The experimental results show that the amplitude fluctuations of Brillouin signals and spectrum parameters are decreased effectively, and SNR is enhanced significantly using three-frequency probe light with 22-time shift-averaging compared to that using single-frequency probe light without shift-averaging, and the highest accuracy of temperature measurement obtained on the 50-m-heated fiber near the far end is 0.36°C, which indicates the proposed approach is effective to enhance performance for a self-heterodyne detection BOTDR.

For a simultaneous phase-shifting interferometer (SPSI), typically four interferograms with different phase shifts are captured at different areas on the detector target by a single-shot capture method. Prior to calculating phase distribution, the region segmentation should be conducted to obtain four separated interferograms. A registration method is also necessary to eliminate the mismatch errors between the interferograms. A spatial mismatch calibration method based on fast partial phase correlation is proposed to register the spatial positions between the phase-shifting interferograms. By tilting the reflective flat, four carrier interferograms are captured to extract four phase distributions using the Fourier transform technique. Partial phase distribution is used as match characteristics to register the interferograms rapidly by employing the correlation operation. The simulation and experimental results show that the ripple error generated by spatial mismatch is suppressed well by the proposed method.

A first-order linear perturbation model for simulating imaging through weak turbulence is introduced and developed. It is based on a first-order approximation of the Born expansion of paraxial propagation. The model generates a random scalar field that encodes information about the imaging parameters, such as wavelength, range, Cn2, and the aperture diameter. The gradients of the field are then multiplied to the corresponding gradients of the average turbulent image of a Lambertian target. The result is a model that can rapidly generate a sequence of turbulent images. Some limitations of the model are discussed, and possible improvements are suggested.

Photoacoustic (PA) imaging for the examination of altered documents in forensic science has been investigated by an innovative system with a nanosecond pulsed laser, a microphone, and a handmade sample holder. The PA signals from lines written by black pens on paper were successfully detected without coupling media such as gels, and the signal amplitude was found to depend on the type of writing pen. The original contents of the document changed by the addition of a line and of the obliterated document were clearly observed by the PA imaging. The nondestructive PA measurement and imaging have been demonstrated to be a high-potential technique to discriminate writing inks and to examine altered documents.

Mobile, all-fiber Doppler wind lidar based on a real-time motion wind retrieval algorithm method is demonstrated. The mobile wind lidar can negate the influences of attitude, velocity, and other factors on the Doppler frequency and is capable of obtaining more accurate real-time mid- to low-altitude wind field information over a large space. In the moving platform test, the measurement error of the wind speed is 0.33  m  /  s, and the measurement error of the wind direction is 5.32 deg.

We report a multipass cell (MPC) that consists of two inexpensive silver (or gold)-coated plane mirrors and a biconvex lens instead of expensive concave spherical mirrors. The silver (or gold)-coated two plane mirrors are separated by a biconvex lens with an inner hole for the detection of the gas flow. The two mirrors (diameter of 50.8 mm) and the convex lens (diameter of 50.8 mm) are mounted on an optical board with a dimension of 75  mm  *  75  mm  *  30  mm and 75  mm  *  75  mm  *  21  mm, and the inner diameter of the two quartz glass tubes is 48 mm with a hole for the detection of the gas in flow and out flow. For example, the plane MPC, which is ∼236  cm³ with 130 times reflections, is much smaller than a traditional concave spherical mirror based on a Herriott or a White MPC, which is ∼700  cm³ with 80 times reflections, and offers an effective optical path-length of about 31.32 m. This low cost, compact MPC is very suitable for various applications, such as climate change, environmental monitoring, and agriculture.

As the critical dimensions of integrated circuits continue to grow smaller, overlay error is becoming increasingly important. Overlay error is mainly determined by the telecentricity of the exposure system in a photolithography tool. Existing telecentricity-measuring methods—which are photoresist-based—are complex and cannot obtain the telecentricity in real time. Moreover, the obtained result is influenced by the photoresist performance. We propose a light-cone-central-line method that measures telecentricity without the need of photoresist. Compared with photoresist-based methods, the light-cone-central-line method can be used in real time, accelerating the setup and tuning of the exposure system and thus significantly reducing the complexities and expenses of the existing measurement methods. The proposed method was applied in a lithography tool with a 90-nm resolution, and the results for five field positions (the center position and four corner-field positions) are presented. This method is found to provide sufficient measurement repeatability, and it satisfies the telecentricity measurement requirements of the tool.

Coherence scanning interferometry (CSI), a type of interference microscopy, has found broad applications in the advanced manufacturing industry, providing high-accuracy surface topography measurement. Enhancement of the metrological capability of CSI for complex surfaces, such as those featuring high slopes and spatial frequencies and high aspect-ratio structures, requires advances in modeling of CSI. However, current linear CSI models relying on approximate surface scattering models cannot accurately predict the instrument response for surfaces with complex geometries that cause multiple scattering. A boundary elements method is used as a rigorous scattering model to calculate the scattered field at a distant boundary. Then, the CSI signal is calculated by considering the holographic recording and reconstruction of the scattered field. Through this approach, the optical response of a CSI system can be predicted for almost any arbitrary surface geometry.

Measuring surface deformation of objects with natural patterns using digital image correlation (DIC) is difficult due to the challenges of the pattern quality and discriminative pattern matching. Existing studies in DIC predominantly focus on the artificial speckle patterns while seldom paying attention to the inevitable natural texture patterns. We propose a recursive-iterative method based on salient features to measure the deformation of objects with natural patterns. The method is proposed to select salient features according to the local intensity gradient and then to compute their displacements by incorporating the inverse compositional Gauss–Newton (IC-GN) algorithm into the classic image pyramidal computation. Compared with the existing IC-GN-based DIC technology, the use of discriminative subsets allows avoidance of displacement computation at pixels with poor spatial gradient distribution. Furthermore, the recursive computation based on the image pyramid can estimate the displacements of the features without the need for initial value estimation. This method remains effective even for large displacement measurements. The results of simulation and experiment prove the method’s feasibility, demonstrating that the method is effective in deformation measurement based on natural texture patterns.

Vibration distribution measurements using interferometers have been evaluated by many researchers. We have used a laser diode interferometer to measure two-dimensional vibration distributions using a combination of phase-shifting and downsampling techniques. Our system simultaneously measured nanometer-order sinusoidal vibration distributions of two objects vibrating at different frequencies, using a charged coupled device camera with a slower frame rate than either of the two harmonic frequencies being measured. This is a cost-efficient and compact system capable of successfully measuring high-frequency vibrations without requiring expensive high-frame-rate cameras.

The shear ratio is an essential parameter of the lateral shearing interferometry system that affects dynamic range, signal-to-noise ratio, and accuracy. Some qualitative conclusions about the shear ratio’s influence can be found in existing reports, but no systematical analysis or quantified universal conclusion has been given. Using the sheared phase to reconstruct wavefront is the unique feature of the shearing interferometry, but it also affects the measurement accuracy significantly. The wavefront reconstruction methods can be divided into zonal and modal methods. We use the FFT reconstruction method and the least-square reconstruction method as the typical methods of modal and zonal methods to analyze the source of the reconstruction error and its relationship with the shear ratio. We conclude that the FFT reconstruction method and the least-square reconstruction method are equivalent to each other. The lost information during the shearing corresponds to some incalculable spectral values in the frequency domain and the pistons of different subgrids in the spatial domain. More spectral information will be lost if the shear ratio increased, which leads to more significant reconstruction errors. When the shear ratios are 1.6% and 6.3%, the corresponding relative reconstruction errors are about 1% and 1%, respectively. The error will be lower if the test wavefront can be represented by a limited amount of basis functions.

Future advances in mass production technologies and the implementation of market creation ideas based on technological convergence can be expected in the lighting sector of the information display market, allowing the development of high-value-added products. The challenges faced, with regard to conventional lighting systems, in achieving an increased manufacturing efficiency via simple processing techniques by utilizing minimal light sources are identified. Consequently, a performance evaluation was conducted for an improvement in the optical characteristics. This was achieved by optimizing the shapes of geometric scattering patterns and the positions of the light sources near the light guide plate (LGP). Based on the results, an effective structure of an LGP for large-area, flat-type lighting systems is proposed. To evenly distribute the incident light, a light-emitting diode (at a beam angle of 60 deg) is placed at each corner of the LGP. Moreover, it was confirmed that the optimum condition for improving the optical characteristics of the applied light is a curved pattern starting from each corner. To increase the illuminance efficiency, this curved pattern is inclined toward the center. Further, the illuminance is approximately doubled (592 lux) when the pattern spacing is reduced, creating an optimal design approach for improving the optical characteristics of a large-area, flat-type lighting system.

We present a highly miniaturized endoscopic point distance sensor based on a spatial confocal measurement principle.¹ The sensor uses a new technique called spatial confocal point distance measurement. A special feature of the proposed sensor design is the high degree of miniaturization through femtosecond direct laser writing and the use of optical fiber bundles, which enable an endoscopic application. We show the complete sensor measurement principle, sensor head design, experimental setup, and experimental results.

We investigate the angular field of view (AFOV) of a holographic image reconstructed from the digital Fresnel hologram in holographic display. The theoretical analysis clarifies that the AFOV of a holographic image is fundamentally determined by the hologram numerical aperture (HNA) other than a diffraction angle of pixel pitch of a pixelated modulator. This property is proved for various types of the digital holograms using a numerical simulation and optical experiments. The high-HNA hologram reconstructs the image with a high viewing angle, whereas the image contraction is inevitable due to the Nyquist sampling criterion in the hologram synthesis. We demonstrate the method for reconstructing the holographic image with a high viewing angle without image contraction.

In the structured light three-dimensional measurement system, calibration is crucial for measurement accuracy. However, conventional projector calibration methods involve complicated procedures. Therefore, a novel method is developed for projector calibration. The key concept is to establish the relationship between projector coordinates and the world coordinates using the projection checkerboard, which enables the calibration of the projector to be the same as that of a camera. In addition, the edges of the checkerboard form different degrees of high-light regions when the projection checkerboard is collected. These high-light regions affect the extraction of corner points and cause low accuracy of the projector calibration. Therefore, the projection checkerboard is collected by a CCD camera equipped with a polarizer at the optimal polarization angle. Then the subpixel corner extraction algorithm based on the homography matrix mapping is used to extract the subpixel coordinates of the corners. Finally, the projector can be calibrated with the same method as the camera. In the experimental part, the validity of the method is verified by the reprojection system.

We have developed a holographic data storage system using angular-multiplexing recording that has a large capacity of 2 TB and a data transfer rate of 1  Gbit  /  s. To read a hologram recorded on a holographic disc at high speed, it is necessary to control the relative position shift between a hologram recorded on a disc and a readout optical system. However, in angular-multiplexing data storage systems, the optical system has no moving mechanism, unlike conventional optical discs such as Blu-ray Discs™. Therefore, it is difficult to control the disc position with high precision and to reduce the settling time of the positioning because the holographic disc has no physical structure for the position control mechanism to control the relative position shift. In the systems, a disc mounted on a disc stage is moved to a position where the signal-to-noise ratio of the reproduced hologram becomes the maximum value. Hence, we present a servo control system based on a shift of the Nyquist aperture using a real-time position error signal to control the disc position. In experiments, a positioning accuracy of ±15  μm and a settling time of 8.5 ms for our angular-multiplexing data storage system using a nonlinear parabolic focus position error signal have been observed.

We have proposed a concave–convex lens for the multiple-input multiple-output (MIMO) visible light communication (VLC) system, which provides more received power than conventional lenses. Ray trajectories using a hemispherical lens, compound parabolic concentrator (CPC), dielectric totally internally reflecting concentrator, and the proposed lens have been simulated in COMSOL software, and it has been shown that the proposed lens provides better convergence at the exit aperture. Also, the images of individual light-emitting diodes (LEDs) are distinguishable, and hence it can support a higher diversity order for the MIMO system. It has been found that our designed lens provides 1.081 times more received power than the hemispherical lens. We have investigated that the average received power using a concave–convex lens is 2.3593 and 1.3737 times more than the received power through bare (uniform refractive index) CPC and gradient-index-based CPC lenses, respectively. We have compared the channel gain using concave–convex and hemispherical lenses considering different values of incidence and half power semiangle of LED. The concave–convex lens has more gain and better volume efficiency; therefore, it can be considered as an appropriate choice for a compact receiver system in an MIMO-VLC system.

An analytical and numerical analysis of light extraction from light pipes using total internal reflection grooves with linear and elliptical profiles is presented. We performed the study considering light sources with different aperture angles, such as sunlight delivered by optical fibers and LEDs. With this analysis, we propose an analytical model based on the edge ray concept that allows selecting the most convenient profile, size, and orientation of the groove to extract light with a desired illumination area according to the source aperture angle employed in the light pipe system. We also have numerically found that for sources with high aperture angles, the light extracted by the linear and elliptical grooves produces similar irradiance and angular distributions, whereas for sources with low aperture angles, the elliptical groove focuses the extracted light and produces a higher angular distribution in comparison to this obtained with the linear groove. Our results are scalable to different light pipe dimensions and provide a systematic way to obtain preliminary designs of grooves for lighting systems that employ optical sources with different aperture angles.

Ion beam finishing techniques are commonly used for improvement of surface error topography of optical devices. Optical aluminum surfaces after manufacturing by single-point diamond turning meet the requirements for applications in the infrared spectral range. However, optics used for applications in the short-wavelength visible and ultraviolet spectral range demand improved surface qualities. To overcome the limitations mainly caused by structural and compositional inhomogeneities of aluminum alloys, a reactive ion beam machining process using oxygen and nitrogen operating gas is applied. This technology enables direct surface machining while preserving the initial roughness up to a 1-μm etching depth using low-energy ion beams. Moreover, the use of oxygen allows us to smooth the surface in the microroughness regime. Based on Monte-Carlo simulations and roughness evolution measured by atomic force microscopy, a more detailed discussion of the ion beam process is presented. Hence, a model scheme for direct smoothing of high-frequency surface features is suggested.

During the production of a lens system, the assembling and manufacturing tolerances must be accurately controlled to ensure production efficiency. Thus, it is important to analyze and optimize the tolerance sensitivity of the lens system during the optical design phase to reduce optical performance degradation. We proposed an approach for appropriately controlling the tolerance sensitivity of a lens system. The proposed sensitivity optimization method can homogenize image performance for the same field under different tolerance values. Based on the results, we show that the implementation of the proposed method sharply reduces sensitivity and, consequently, improves the product yield rate by 15 to 17% compared with a traditional optimization method. As a practical example, a 40-megapixel f1.8 mobile phone camera lens design and optimization process was performed in our study. Our preliminary experimental results confirm that the proposed method is effective to reduce the optical sensitivity of the camera lens.

The millimeter-level bidirectional long-distance asynchronous ranging has long been a huge challenge in the field of measurement and instrumentation. Correspondingly, a laser pseudocode ranging algorithm based on regenerative synchronization mechanism is proposed to address the problems obstructing precise distance measurement between asynchronous satellites. First, the synchronization strategy of a double-ended asynchronous terminal based on the regenerative pseudocode is discussed. Subsequently, we look at the algorithm of the generation, transmission, detection, and the code phase tracking loop, which forms the base of obtaining high precision of pseudocode ranging. On this basis, the error of laser pseudocode ranging link is analyzed, which mainly incorporates receiver noise and clock error. In terms of receiver noise, the influence of the photodetector carrier-to-noise ratio on random noise distribution is evaluated, and the design of receiver parameters is guided as such. As for the clock error, we look at the constraint relationship between the range and the precision under the action of the clock error, which provides the basis for the selection of the clock. Finally, the optimized system is tested when a double-ended laser link is set up in the laboratory. As a result, the comprehensive accuracy results of 3.47 mm systematic error and ±1.73  mm random error is obtained, and the long-scale measurement performance has been tested by the temperature-compensated crystal oscillator pulse frequency experiment. In conclusion, the experiment is consistent with the theory proposed in this study, which provides a theoretical and experimental basis for long-distance high-precision intersatellite ranging.

We propose a silicon microring modulator based two-circular quadrature amplitude modulation (16QAM). We have numerically analyzed the error performance using Voronoi diagram and compared it with the simulation results under back-to-back condition using optical band-pass filter (OBPF) before the receiver having 3-dB bandwidth of 30%, 40%, and 50% of symbol rate, respectively. The result shows 1 dB difference between each case of OBPF bandwidth and 0.5 dB difference between theoretical and simulated value.

A laser-induced cavitation-based sterilization technique was demonstrated to efficiently inactivate foodborne pathogenic bacteria with a low loss of nutrients. A sterilization efficiency of more than 90% (less than 5  ×  10⁵  colony-forming unit  /  mL) was achieved when the flow rate was no more than 40  μL  /  s on a chip that could mimic an industrial sterilization system. In addition, the sterilization efficiency could be enhanced if the channels of the chip were coated with Ta₂O₅  /  SiO₂ film. Moreover, the nutrient composition of the milk was well preserved. The laser-induced cavitation-based sterilization technique provides an alternative method for the inactivation of foodborne pathogenic bacteria.

Due to the thermal-induced stress during the bonding process, the emitters in a laser diode array (LDA) are vertically displaced, which causes the near-field bowing of a laser diode bar (i.e., the SMILE effect). Near-field bowing degrades the laser beam brightness, adversely affecting optical coupling and beam shaping, resulting in a larger divergence angle and a wider line after focusing and collimation. The mechanism of near-field bowing has been theoretically studied, in which the ratio of tensile strength between submount and heat sink has a great effect on the deformation of LDAs. Arm-wrestling between CuW submount and heat sink vividly describes that the deformation of LDAs changes as a function of the ratio of two materials’ tensile strength. We design a symmetrical structure that bonds another submount on the bottom of the heat sink to control the SMILE effect by balancing the acting force from the top of the heat sink. The deformation of the heat sink and LDAs are approximately zero when the thermal-induced stresses forced on the top and bottom of the heat sink are equal.

We discuss the design of a digital laser communication receiver and its sensitivity test process. Laser communication is especially suitable for long-distance low-power micro–nano satellite links due to its narrow beam width, but the electro-optical noise situation of the micro–nano satellite platform is complicated and bad. Hence, it is necessary to introduce a digital laser communication receiver to flexibly suppress interference and noise to improve communication sensitivity. A digital laser communication receiver based on the avalanche photodiode (APD) is designed. Based on the principle of digital communication error probability, a high-sensitivity APD device is selected, and a digital receiving channel based on field programmable gate array is designed. The finite impulse response, the dynamic threshold, the baseband median, and other filtering algorithms are used to optimize the signal-to-noise ratio and enhance the detection sensitivity. At the same time, an 800-nm laser communication receiver sensitivity test experimental architecture is designed and the detection sensitivity experiment is carried out. The experiment indicates that the APD receiver achieves detection sensitivity at an Mbps rate better than −60  dBm. The digital filtering algorithm provides a filtering signal-to-noise ratio improvement of about 15 dB, which supplies a reference for the receiver design of micro–nano satellite laser communication.

The temperature response of a tapered holmium-doped fiber amplifier and its impact in the performance of fiber lasers and temperature fiber sensors has numerically been analyzed. Different pump schemes and different longitudinal shapes of the tapered-doped fiber were investigated, and it was found that a parabolic shape of the tapered fiber amplifier in a co-propagating pump scheme shows the highest sensitivity to temperature changes. In particular, the temperature sensitivity of the amplified signal was 2.5  ×  10^−  4  °  C for 1 W of pump power and 1 m of doped fiber length. In addition, this sensitivity can be increased up to 10 times for fiber lengths shorter than 1 m and pump powers lower than 300 mW. Our results can be used to describe the temperature response of tapered fiber amplifiers in the mid-infrared spectral region and contribute with new information for the development of fiber lasers and fiber temperature sensors.

The piezoelectric ringing phenomenon for the Pockels cell with DKDP crystal is analyzed. The dependencies of contrast ratio of Pockels cell with the DKDP crystal on high-voltage pulse duration in the range from 100 ns up to 5  μs and on the pulse frequency in range from 50 Hz to 250 kHz are obtained and analyzed. Measurements that map the piezoelectric ringing amplitude distribution in the aperture of the DKDP crystal of the Pockels cell are performed as well.

For the first time, a dynamic model is used to design all-optical polarization rotator for ultrashort pulse in semiconductor optical amplifier (SOA). When 200 fs probe and pump pulses co-propagate in SOA, the azimuth angle of probe polarization is rotated by pump energy due to SOA nonlinearities. As a result of azimuth angle rotation (AAR) phenomenon, the state of polarization (SOP) of probe pulse also rotates. In addition to the pump energy, AAR also depends on the input probe pulse characteristics and the SOA bias current. The input probe characteristics include its input energy level, input Stokes vector, and input degree of polarization. The results of our research indicate that the output probe azimuth angle can be rotated up to 113 deg by the mentioned factors. Consequently, the probe SOP can be changed from the quasihorizontal state to the quasivertical state.

Erbium-doped fiber amplifier (EDFA) is widely used in the optical communication system, and it is usually used as a linear amplifier in most scenarios. However, in analog photonic links, we observe the nonlinear spurs caused by EDFA. In the analog photonic link, the dynamic range is one of the most important characteristics while the nonlinear spurs set the upper limit of input signal power. We study the nonlinearity caused by EDFA in analog photonic links when the input power of EDFA fluctuates at a low frequency. We have theoretically and experimentally studied the characteristics of the nonlinear spurs caused by EDFA.

We propose an optical approach to estimate the angle of arrival (AoA) of a microwave signal. The microwave signal and its phase-shifted replica received from separated antenna elements are applied to a null-biased dual-drive Mach–Zehnder modulator. An optical loss resonance at the optical carrier is introduced by stimulated Brillouin scattering in optical fiber. By measuring the resultant optical power, we can obtain the phase difference, from which the AoA of the incoming microwave signal can be determined. An experiment is carried out, which exhibits that phase measurement errors are <1.86  deg with a phase difference from 9 deg to 162 deg.

Regenerative amplifiers containing multiple diverse laser heads have the ability of scaling up output power as well as broadening spectral bandwidth. However, the thermal lensing effect will be more complicated. A method using a 4f system to simplify the thermal lensing effect in a multidisk condition is proposed. Two kinds of Yb-dropped sesquioxide materials are chosen as an example. On the basis of calculating the thermal lensing parameters of the thin-disk laser heads, a feasible cavity design that can minimize the fluctuation of beam size when changing the pump power is given out. The 4f system consisting of concave mirrors will introduce astigmatism in the cavity. The influence of astigmatism and the compensation method are discussed. Astigmatism can be compensated by adding extra convex mirrors and controlling the angle of incidence at each mirror.

In the resonant optical gyro, the stability of light intensity is crucial for obtaining good dynamic and static performance characteristics. In this work, the effects of the laser intensity fluctuation on the scale factor nonlinearity and Kerr effect error were studied by combined experimental and theoretical analysis. Then, a simple light intensity feedback loop was designed using an intensity modulator, and the light intensity was calibrated in real time using the maximum value of the second harmonic demodulation curve. Experimental results show that the fluctuations of the light intensity entering the gyro system are reduced by about two orders of magnitude through the use of the light intensity feedback loop. The system scale factor nonlinear error was decreased from 13.74% to 2.79% and the dynamic performance of the gyroscope was improved. Additionally, the long-term (1 h) bias stability of 16.94  deg  /  h was obtained.

We demonstrated a middle-wavelength infrared (MWIR) graphene photodetector using the photogating effect. This effect was induced by photosensitizers situated around a graphene channel that coupled incident light and generated a large electrical charge. The graphene-based MWIR photodetector consisted of a top graphene channel, source–drain electrodes, an insulator layer, and a photosensitizer, and its photoresponse characteristics were determined by current measurements. Irradiation of the graphene channel of the vacuum cooled device by an MWIR laser generated a clear photoresponse, as evidenced by modulation of the output current during irradiation. The MWIR photoresponse with the photogating effect was 100 times greater than that obtained from conventional graphene photodetectors without the photogating effect. The device maintained its MWIR photoresponse at temperatures up to 150 K. The effect of the graphene channel size on the responsivity was evaluated to assess the feasibility of reducing the photodetector area, and decreasing the channel area from 100 to 25  μm² improved the responsivity from 61.7 to 321.0  AW^−  1. The results obtained in our study will contribute to the development of high-performance graphene-based IR imaging sensors.