This PDF file contains the front matter associated with SPIE Proceedings Volume 12711, including the Title Page, Copyright information, Table of Contents and Conference Committee lists.

A novel spectrum reshaping approach of scanning amplitude limiting based on Optical Kerr effect is proposed to overcome the undesirable spectral gain narrowing and blueshift effect in chirped pulse amplification (CPA). The theoretical analysis of the scheme is demonstrated and the reshaping performance of F-P interference filtering device with built-in Optical Kerr medium are simulated and discussed. For the initial Gaussian spectrum of chirped pulse with ns magnitude of 800nm central wavelength and 20nm bandwidth, the "saddle shape" and "blue shift" spectrum are obtained by the proposed spectrum reshaping approach. The theoretical analysis and numerical simulation show that the spectrum of chirped laser pulses can be reshaped flexibly by the proposed scanning amplitude limiting method based on Optical Kerr effect. Furthermore, it is necessary to reduce the deviation of pump intensity as much as possible so as to match the reshaped spectrum with the desired spectrum.

Color cameras are widely used in many fields such as printing industry, graphic arts, medical treatment, and environment. On the premise of saving cost, in order to ensure that the color rendering effect of the camera is as close as possible to the imaging of the human eye, a method of using color filters to correct the total spectral response curve of the color camera is proposed. The principle of correction is to make the total spectral response of the system meet the Luther condition. By adding such a filter, the adjusted camera sensitivity function can be very close to a certain linear transformation of the color matching function of the human visual system. Due to the manufacturing process, the transmittance of the produced filter can only be a smooth curve. Starting from the factors that affect the accuracy of the filter simulation, we express the transmittance of the filter as a certain smoothness in the calculation process combination of basis functions. Different basis functions will lead to different results. Here we use discrete cosine transform basis functions, polynomial basis functions, Fourier basis functions and radial basis functions to conduct experiments. Under the condition of each basis function, a corresponding optimal spectral transmittance curve will be obtained. Taking the 14 standard test colors recommended by the International Commission of Illumination as a reference, the CIE1976 color difference formula is used to calculate the theoretical color difference of the corrected camera under the condition of different basis functions. Finally, the performance of the basis function is evaluated from three indicators: Vora-Value, NRMSE and color difference.

Thermal emitter, as one of the important components in the thermal photovoltaic system, is mainly used to absorb the energy radiated by the heat source and convert it into energy that can be absorbed by the photovoltaic cell. We use the RCWA algorithm to optimize the thermal emitter based on the refractory metal Mo microhole array with a quadrangular arrangement. The optimized structure has a high selective emissivity characteristic in the 1-2.4 μm waveband. The averaged emissivity can reach more than 79.6%, which is about 60% higher than that of the unstructured emitter; at the same time, the band emissivity gradually decreases after the wavelength of 2.4 μm, achieving a selective emission control. Using the laser direct writing technology, dry metal etching, and other micro-fabrication techniques, the thermal emitter is fabricated with the feature sizes as follows: the hole diameter, the array period, and the hole depth are 1 μm, 1.4 μm, and 3.4 μm, respectively; the area with microhole structures is 12×12 mm. The experimental measurement suggests that the averaged emissivity arrives at 70.07%. This study provides an alternative candidate for selective thermal emitters and also offers a technical experience for practical applications.

Metamaterial induced transparency (MIT) has great potential in photonic device applications. Here, we design a metastructure with MIT effect generated by destructive interference of bright-dark-dark three modes. Therein, the cross resonator formed by the combination of the cut-wire resonator and the long vertical metal bar (LVMB) act as the bright mode, and two pairs of split ring resonators of different lengths are distributed around the cross resonator as two dark modes, realizing significant multi-band MIT effect. Furthermore, the embedded photosensitive Si island in the broken LVMB can be used to tune the effective length by changing the conductivity, thereby actively controlling the conversion from multi-band behaviors into triple MITs. Our results could achieve the dynamic multi-band switching, which has broad application prospects for optical information processing and communication.

Terahertz (THz) waves have great potential applications in communication, imaging, and spectroscopy fields. Effective THz modulators are highly desired to realize those functionalities. Wherein, as a kind of artificial composite material, THz metamaterials can achieve extraordinary responses to the electromagnetic wave through the geometric structure design. Nevertheless, normal metamaterials have no tunability once they have been designed and fabricated. To overcome this issue, active medias have been explored to enable the expected modulation of metamaterials under the external stimuli. Among them, phase transition materials are often used in dynamically tunable THz devices due to their intriguing properties. Particularly, vanadium dioxide (VO2) has attracted attention owing to the reversible physical properties and can exhibit insulator-to-metal transition (IMT) behavior at near room temperature. Here, we explore the strength of the resonance response and the change of spectral lineshape caused by the size variation in the metamaterial unit cell. On this basis, adding VO2 thin film can realize broadband modulation during the IMT process. Furthermore, by incorporating the VO2 patches in the gold microstructure can further achieve the dual modulation of amplitude and frequency simultaneously. The design of VO2 hybrid metamaterial can break the single function limitation of traditional metamaterial modulators, reduce material loss, and open up a new path for the development of multifunctional THz modulators.

Metamaterial induced transparency (MIT) has shown great application potential in terahertz regime, which is of great significance in constructing photonic components such as slow light systems and tunable filters. The single or multiple transparent windows can be induced through near-field coupling via two or more resonant modes. Compared with the single MIT, multi-MIT effect can realize multiband sensing, communication, and storage applications. Here, we design a dual-MIT metastructure composed of three bright resonators including a cut-wire resonator (CWR), a pair of large toroidal split ring resonators (LTSRRs), and a pair of small toroidal split ring resonators (STSRRs). Dual-MIT windows can be induced through coupling between the electric dipole resonance and two inductance capacitance (LC) resonances. By optimizing and adjusting the geometric parameters of the metasurface, the resonant strength could be suppressed or enhanced. Thus, we can passively manipulate the frequency and amplitude of the dual-MIT windows and realize the switching between the two windows and single MIT. In addition, by actively tuning the conductivity of photosensitive Si introduced in the gap of the LTSRRs and STSRRs, we observe the LC resonance can be weakened to quench the dual-MIT windows. Our research provides an approach to explore the miniaturized, multi-functional, and switching components in terahertz regime.

Dual-scale structures with chemical modification were fabricated on the titanium surfaces by a combination of a picosecond (ps) laser parallelly direct writing microstructures, a femtosecond (fs) laser inducing nanoripples and a chemical solution modification. Two kinds of microstructures (microholes and mircopillars) were created at different intervals for comparison, and nanoripples were induced dividually, which provided possibility to evaluate the roles of structures and chemistry. After each step, the samples were cleaned in ultrasonic cleaning machine and stored in seal bags to suppress interferences. The results showed that low surface energy is necessary for hydrophobic on titanium surface, and mircopillar had a greater capacity of wetting regulation. In additions, a “structures saturation effect” was also found, which were disagree with the Wenzel model.

In hazy scenarios, suspended particles in the atmosphere will absorb and scatter the transmitted natural light, resulting in a serious degradation of image quality obtained by imaging equipment, which greatly affects the visual perception of images. Aiming at the problems such as low contrast, color distortion and lack of detail information in areas with high haze concentration in images acquired by image acquisition equipment in hazy days, this paper proposes a dehazing algorithm based on exposure image fusion based on multi-logarithmic transform, which improves image quality while effectively dehazing images and avoids the edge effect in the sky part of images after dehazing. Firstly, the original hazy image was transformed by logarithmic multiple times to produce multiple images with different exposure to be fused. Then, all the input images with logarithmic transformation and weight graphs were fused by multi-scale pyramid fusion method to obtain the dehazing image. In order to verify the effectiveness of the algorithm in this paper, the results of the proposed algorithm and six mainstream image dehazing algorithms are compared in two aspects: subjective evaluation and objective evaluation. Experimental results show that the image processed by the proposed algorithm presents better visual effects than that processed by other algorithms. The proposed algorithm can effectively improve image contrast, improve image distortion, improve the visibility of detail information in areas with high hazy concentration, and the scenery color is natural. Good results are obtained under two objective evaluation indexes of image quality, namely peak signal-to-noise ratio and structural similarity, which further proves that the algorithm proposed in this paper has good dehazing performance, can effectively improve the image visibility, and has a good overall color preservation degree of the image.

Spintronic terahertz emitters (STEs) with the feature of high performance and low cost have been a hot spot in the field of terahertz sources. However, little attention has been paid to the control and modulation of the THz waves generated by the STE. In this paper, we propose a unidirectional spintronic terahertz emitter (USTE) integrated a common STE with a metal grating. The dyadic Green’s function method and finite element method are adopted to survey the characteristics of the USTE. Simulation results show that the metal grating has a transmission larger than 97% in the optical band. Meanwhile it also has a higher reflectivity larger than 99% in the THz band. As a result, the USTE has a unidirectional THz emission along the direction of the pump beam with a larger than 4-fold enhancement in intensity. Besides, the USTE has the capability of tuning the central frequency. We think that this USTE can be used in THz wireless communications and holographic imaging, especially in the field of THz bio-sensing, which needs some resonance frequencies to sense.

The impact of the interface effect on the etching accuracy of a non-single-layer structure was utilized as a starting point in this work to analyze the correlation between the integrated structure's film surface/interface temperature field, stress field distribution, and interface mutation. Based on single-factor etching experiments, the relationship between the temperature field, stress field, and laser characteristic parameters was evaluated via a combination of theoretical analysis and numerical simulation. For polyimide-based metal aluminum film, a connection between scanning speed and etching characteristic parameters was discovered. The results illustrate that when Al/PI (aluminum film thickness of 2μm) was irradiated by a laser, the interface temperature reached a certain value, which caused distortion of the film and substrate. Changes in the distribution of the temperature and stress fields of the film affect the heat transfer in the system and thus affect the thermodynamic trajectory, thermal feedback, etching rate, and shape of the target film surface. Ultimately, the etching and removal of the Al/PI integration of the non-single-layer structure are attributed to the interplay of thermal and stress field effects.

Non-destructive testing technology for large grinding wheel geometry is getting more and more attention from the industry. A device based on machine vision technology for intelligent measurement of large grinding wheel size is introduced. After calibrating and measuring the inside and outside radius of the grinding wheel and the thickness of the grinding wheel, intelligent detection is realized through a series of operations such as binarization of the original map, filling, expanding, outline extraction and outline coordinate extraction through hardware design and software programming. The hardware requirements of this design are simple. When measuring the radius of a grinding wheel, the method described in this paper gives the results of radius and height measurements with accuracy up to 5mm and 1mm, respectively. Finally, through repeated measurement experiments, the intelligent detection device of large grinding wheel size established in this paper can effectively solve the problems of field calibration of large grinding wheel and fast detection of inside and outside diameters.

The existing fire alarm system has strict distance and installation requirements between the fire point and the detector, and is easy to be interfered by environmental factors. It is not suitable for places with large space and many interference factors such as Climbazole production line. This paper proposed a flame image detection technology based on RGB+HSI color model and the detection system is designed and developed. The experimental results show that the flame image detection system based on RGB+HSI color model has the better recognition efficiency, which meets the real-time and accuracy requirements for early flame image detection in Climbazole production line.

Visible light communication (VLC) has attracted attention due to its promising future. However, the low bandwidth of the light source leads to the relatively low communication rate. In this work, a measurement platform mainly consisted of signal source and oscilloscope is established to measure the 3-dB modulation bandwidth of LED. Experiments are conducted to investigate the influences of the LED’s working current, distribution of LED array, and LED’s driving circuit on the working bandwidth of the VLC system. When the LED driving current increases from 22 mA to 32 mA, the corresponding 3-Db bandwidth of the blue LED is improved from 1.8 MHz to 2.3 MHz. Designing blue LED array with the controlled internal distance between the neighboring LEDs aimed at improving the overall working bandwidth of the commercial light sources. The 3-Db bandwidth of a single blue LED is 1.8 M under the working current of 20 mA. The 3- dB bandwidth of the 2×2 blue LED array in series is 2.9 M under the working current of 20 mA with the optimized internal distance of 10 mm. Under the same measurement conditions, the 3-Db bandwidth of 1×2 blue LEDs in parallel is improved from 1.8 M to 2.9 M after adding the as-designed LED driving circuit.

Constructing novel hybrid nanostructure has become an effective strategy to enhance the performance of photoelectrochemical (PEC) biosensors. However, most of the H₂O₂-sensing photoelectrodes require enzyme modification, which limits the working environment and sensing performance. Herein, the burr-like CuO nanostructures are modified on the entire surfaces of the ordered Si nanowires (SiNWs) by using a combination of magnetron sputtering and hydrothermal growth. The optimized CuO@SiNWs heterojunction with a core-shell structure enables enzyme-free PEC detection of H₂O₂, achieving a sensitivity of 227.76 μAmM^-1cm^-2 in the concentration range of 0–588 mM and a detection limit of 7.14 μM (Signal/Noise=3). The excellent sensing performance of the CuO@SiNWs is attributed to the large specific surface area provided by SiNWs and the CuO possess desired H₂O₂-catalytic activity while providing a great number of active sites. In addition, the CuO@SiNWs demonstrates satisfactory optical absorption. This work demonstrates that enzyme-free and highly sensitive H2O2 detection can be achieved by hybrid nanostructure, providing an alternative route to H₂O₂ sensing.

A domestic space-borne transportable FP cavity is designed. The cavity length is 100 mm with the shape of a cube. Spacer is made of ultra-low expansion glass. This cavity is four-point mounting and heat insulated from external environmental fluctuation. To judge the performance of this cavity, an ultra-stable laser based on this cavity was constructed, the frequency noise of which is below 30Hz/√ Hz, which can fulfill the requirements of the Taiji-2 mission.

This article presents a novel method to simultaneously measure the six-degree-of-freedom (6-DOF) absolute position and attitude based on light spots. The proposed system consists of a measurement unit and a moving target: the measurement unit contains a laser, three cube corner retroreflectors (CCR), three CMOSs, and some beam splitters; the target is a cube with three CCRs installed on each of its three orthogonal planes. In the measurement unit, the laser is split into three reference lights as well as three measured lights which are detected by three CMOSs after returning from six CCRs. Based on the vector analysis of the optical path, the relationship between 6-DOF position and attitude of the moving target and the output coordinates of three CMOSs is established. This method is capable of simultaneously measuring translational motions along as well as rotational motions around three orthogonal axes and achieving the absolute positioning of the target, which has overcome the shortage that the measurement systems based on laser interference can not measure absolute position and attitude. The accuracy of this method has been verified by Monte Carlo stochastic simulation and sinusoidal trajectory simulation in the range of the target’s motion. The simulation results show that the errors of position are less than 0.5 μm and the errors of attitude are less than 2.3 ″, which indicates the algorithm error is no more than the minimum pixel size of CMOS. This 6-DOF absolute pose simultaneous measurement method with simplicity and high precision has great potential for application in various precision machining fields.

Photoelectrochemical (PEC) sensors have the advantages of high sensitivity, low background noise, and fast response time, and are suitable for environmental monitoring, biomedical, and chemical industries. In this work, a photocathode whose photoresponses weaken with increasing concentration of the substance is proposed and used for Cr(VI) sensing, and a wide concentration range (0.04−16 µM) for Cr(VI) can be detected by just using one NiO film, with a sensing sensitivity of 0.69 lgC µAµM^-1 cm^-2 (where C is the concentration) and a low detection limit of 0.01 µM. The successful detection of Cr(VI) was achieved through the signal-weakening photoelectrochemical responses, as evidenced by the decrease in the photocathode signal with increasing Cr(VI) concentration. This can be attributed to the steric hindrance effect caused by the in-situ formation of Cr(OH)₃ precipitates. Our proposed scheme can be successfully used for the monitoring of Cr(VI) in drinking water, as the world health organization requirement of 0.96 µM is included in the linear detection range.

Binocular stereo vision technology has good application prospects and practical value in industrial production, autonomous driving, quality inspection, and many other aspects, and is an important research direction in computer vision. Strain measurement based on binocular stereo vision is different from traditional strain measurement methods, and has advantages such as convenient operation, high accuracy, and global dynamic measurement. This article focuses on the strain measurement technology of binocular stereo vision, and studies the camera calibration, stereo matching, 3D reconstruction, and SGBM algorithm in stereo matching of binocular cameras. By constructing a binocular camera strain testing system, the distance between the corresponding point AB before and after the strain of the target object is measured, thereby achieving the measurement of the strain of the target object. The strain of the target object obtained from the experimental test results is 47.53%, the theoretical tensile strain is 48.54%, and the relative error is controlled within ± 2%.

The tunability of optical transmittance spectra can be available by mounting one of the mirrors of the Fabry-Perrot cavity on a movable structure. The F-P filter prepared by adopting MEMS process can realize the advantages of miniaturization, array, and high output. The size of the MEMS F-P filter can be reduced to a few hundred micrometers. This feature introduces a new problem for the characterization of optical performance, that is, the incident light needs to be focused onto the mirror with a size of a few hundred micrometers. However, in the actual test, the incident light with a hundred-micron spot is usually a convergent beam with a certain cone angle. It is found that through theoretical analysis, compared to parallel incident light, the convergent light beam passed through the F-P cavity leads to the decrease at peak transmittance and the broadening of full width at half maximum. The reason for that was the converging light with a cone angle passing through the F-P cavity had different incident angles and caused diverse optical path difference. As a result, the light emitting from the cavity with various wavelength would appear in the transmission spectra. In summary, the test results under the converging light could not truly reflect the performance of the F-P cavity and the influence of the cone angle of incident light beam on the performance characterization of MEMS F-P filter was analyzed by theoretical arithmetic and simulation.

All-perovskite tandem solar cells (TSCs) show an effective way to overcome the efficiency limit of single-junction perovskite solar cells (PSCs). Low-bandgap mixed tin-lead perovskite bottom subcell is a critical component in all perovskite TSCs, which are currently limited by the relatively low efficiency and poor stability of the bottom subcells. Here in this work, we use multifunctional taurine material to dope and modify the PEDOT:PSS hole transport layer (HTL) for better optical transmittance and charge transporting properties, enabling efficient low-bandgap PSCs with highly improved open circuit voltages and short circuit current densities. Taurine has a suitable refractive index to reduce light reflection loss when introduced at the interface of PEDOT:PSS/perovskite film. Moreover, taurine improves the energy level alignments and facilitates charge transfer dynamics in the low-bandgap PSCs when doped into the PEDOT:PSS HTL. Finally, the synergistic effects of the interface modification and bulk doping of PEDOT:PSS with taurine leads to significantly enhanced efficiencies of over 22% and 26% for low-bandgap PSCs and all-perovskite TSCs, respectively.

In this paper, we presented the inscription and sensing characteristics of eccentric fiber Bragg gratings (EFBGs) through femtosecond laser. This kind of fiber grating is caused by localized refractive index modulation that deviates from the center of the fiber core. EFBGs were prepared in SMF-28 single-mode fiber by 800nm femtosecond laser point-by-point writing method. The temperature and refractive index sensing properties of the prepared EFBG were investigated. The experimental results show that both the Bragg wavelength and cladding mode resonance wavelength of EFBG increase linearly with temperature and show extremely high-temperature robustness. The temperature sensitivity of Bragg resonance is 14.4 pm/℃. As the SRI increases, the Bragg peak remains unchanged and the cutoff wavelength of EFBG cladding mode resonance red-shifts with a sensitivity of 649.29 nm/RIU.

Aiming at the requirement of accurate simulation of near-space atmospheric infrared background radiation, this paper simulates near-space infrared atmospheric background radiance according to atmospheric parameters detected by satellites. The multi-channel infrared radiometer SABER (Sound of the Atmosphere using Broadband Emission Radiometry) carried by TIMED satellite (Thermosphere, Ionosphere Mesosphere Energetics and Dynamics) is used to acquire atmospheric profile. Combined with limb observation model and atmospheric background radiance calculation model, the transmittance and spectral radiance of infrared atmospheric background were simulated. The spectral radiance of atmospheric background under the standard atmospheric model and satellite atmospheric profiles was compared to analyze the difference between the two atmospheric parameter. In the infrared band, the atmospheric profile has a great impact on atmospheric background radiance. For the accurate simulation calculation of infrared background spectral radiance in different regions, the influence of atmospheric profile parameters should be taken into account.

The non-equilibrium ultraviolet radiation characteristics of plume and shock are closely related to flight parameters such as vibration-rotation temperature, where temperature is the most important thermodynamic quantity for calculating non-equilibrium radiation. CN is the main product of aircraft reentry into the atmosphere and the ablation of carbon-based composite materials, and has very high emission efficiency, making it one of the best molecules for high-temperature gas temperature measurement. In this paper, the two-temperature model and the line-by-line method are used to calculate the CN ultraviolet spectral radiance, and the spectral structure of the violet band is analyzed. The effects of vibration temperature and rotation temperature on the spectral intensity and spectral shape of ultraviolet radiation under thermodynamic non-equilibrium conditions are discussed. According to the relationship between the band tail of CN violet band v=0 peak and the vibration temperature and rotation temperature, a method to invert the rotation temperature using the the slope of CN spectral relative intensity

An hollow-core terahertz fiber applying anti-resonant Bragg structure as the basic unit is proposed. Simulations results shown that the proposed THz fiber shows both the transmission characteristics of a conventional anti-resonant structure and a Bragg fiber. The confinement loss of which could be two-three orders of magnitude lower than that of an anti-resonant structure fiber consists of a single anti-resonant ring, and the total loss is one order of magnitude lower, the transmission loss of the proposed THz fiber could be 0.5 dB/m or less with a relative wide bandwidth of 0.15 THz.

Conventional enzyme-based glucose sensors have good selectivity and sensing performance, but the disadvantages of the enzyme itself (enzyme activity is susceptible to pH and temperature) lead to a limited number of uses and result in high costs. Therefore, photoelectrochemical enzyme-free glucose sensors have attracted research interest in recent years. In this work, the TiO₂/CuO heterojunction was constructed and photoelectrochemical enzyme-free glucose sensing was realized. The sensing sensitivity of the TiO₂/CuO heterojunction photoelectrode prepared by magnetron sputtering and thermal annealing process was 864 μAμM^-1 cm^-2 in the range of 1–9 mM with a detection limit of 58.6 μM at 0.2 V, exhibiting satisfactory stability as well as interference resistance. This better sensing performance mainly comes from: 1) the absorption of photogenerated carriers generated from sunlight by TiO2 films, which participate in glucose redox; 2) the conversion of the metal valence state (Cu²⁺/Cu³⁺) of the P-type semiconductor CuO under alkaline conditions can promote glucose redox; 3) the heterojunction formed by CuO and TiO₂ reducing the compounding of photogenerated carriers thus improving the photoelectric conversion efficiency. The heterojunction formed by CuO and TiO2 greatly facilitates the surface carrier transfer of glucose oxidation reaction. This work provides a new way for enzyme-free glucose sensing and promotes the development of glucose detection technology.

In non-steady and high-speed flowing high-temperature environments, local thermal non-equilibrium phenomena are widely present. Therefore, if the Boltzmann distribution, which uses a single temperature to describe the energy level distribution of molecules, is adopted, a large error may exist. To solve this problem, a two-temperature / three-temperature model is often used to calculate the spectral radiation characteristics of OH in local thermodynamic non-equilibrium states. In this paper, taking the BSUV-2 aircraft at a flight altitude of 100 km as an example, The OH radiation characteristics in shock waves with a wavelength range of 305nm-315nm were calculated using the two-temperature model. By comparing the relative spectral radiance of experimental spectra and calculated spectra of OH, the optimal calculation range of vibrational temperature was determined to be 2000K-4000K. This method of measuring rotational temperature has significant advantages in low-resolution situations. After determining the rotational temperature, by simulating and calculating the normalized OH spectral radiance corresponding to different vibrational temperatures in the wavelength range of 270nm-340nm, it was found that the maximum intensity peak G1 is not affected by temperature, while the second largest intensity peak G2 has a linear relationship with temperature. Therefore, we can use the ratio of G1 to G2 to invert the range of rotational temperature. This study shows that using a two-temperature thermodynamic non-equilibrium model in local thermodynamic non-equilibrium states can achieve temperature inversion and accurately describe the spectral radiation characteristics of OH molecules, providing an important reference for related research fields.

The 1319 nm laser is widely used in sodium beacon, optical communication and laser medical fields, and also a potential pump source for 4.3 μm output. In this work, we reported a laser diode partially end-pumped Nd:YAG slab laser operation at 1319 nm. A stable plano-concave cavity was adopted. The maximum continuous output power of 24.33 W was obtained for the absorbed pump power of 222 W, exhibiting an optical conversion efficiency of 10.96% and a slope efficiency of 23.06%. The beam quality was measured to be M2 = 1.19 in the vertical direction.

An experimental scheme based on interferometry is designed to measure the orbital angular momentum spectrum of vortex beam perturbed by turbulence. The orbital angular momentum spectrum of vortex beam can be calculated by using four light intensity images. The laser beam is modulated by a spatial light modulator to obtain a vortex beam, and then passes through another spatial light modulator loaded with a turbulent phase perturbation hologram to interfere with the reference beam. The orbital angular momentum spectrum of the vortex beam can be obtained by making use of two interference patterns and the intensity patterns of the vortex beam and the reference beam. The results show that the experimental scheme can measure the orbital angular momentum spectrum of the vortex beam affected by turbulence.

In the traditional Fourier single-pixel imaging (FSPI), compressed sampling is often used to improve the acquisition speed. However, the reconstructed image after compressed sampling often has a lower resolution and the quality is difficult to meet the imaging requirements of practical applications. To address this issue, we proposed a novel imaging method that combines deep learning and single-pixel imaging, which can reconstruct high-resolution images with only a small-scale sampling. In the training phase of the network, we attempted to incorporate the physical process of FSPI into the training process. To achieve this objective, a large number of natural images were selected to simulate Fourier single-pixel compressed sampling and reconstruction. The compressed reconstructed samples were subsequently employed for network training. In the testing phase of the network, the compressed reconstruction samples of the test dataset were input into the network for optimization. The experimental results showed that compared with traditional compressed reconstruction methods, this method effectively improved the quality of reconstructed images.

Defocus blur in images is often the result of inadequate camera settings or depth of field restrictions. In recent years, with the emergence and advancement of deep learning, learning representation-based methods have achieved remarkable success in the field of image defocus enhancement. In this paper, a rapid axial scanning system was proposed for efficient acquisition of defocused-enhancement datasets. A multi-focus image sequence with different focus depths of a same scene is captured, and it is utilized to generate a full-focus image (ground truth) through image fusion, to build a set of defocused enhancement datasets. Multiple defocused-enhancement datasets can be obtained based on this approach. Experimental results confirm the feasibility and effectiveness.

An optimization algorithm for binary amplitude-only hologram (BAOH) based on the point source method (PSM) with the holographic viewing window (HVW) by using particle swarm optimization (PSO) is proposed. We convert the 256 grayscale levels of each pixel of the original image into an 8-bit binary format and sequentially extract the effective bits of each pixel to generate eight frames of binary original images. Then we introduce random constant phases to be optimized on the wavefront phase of the point source to superimpose the wavefront and generate a grayscale hologram with Burch encoding and binarize it. PSO algorithm is used to search for the optimized constant phase (OCPs) corresponding to each point source wavefront to generate an optimized BAOH. The grayscale representation of the reconstructed image is achieved by sequentially loading eight frames of BAOH on the digital micromirror device (DMD) while controlling the pulse width doubling the illumination of the laser. Simulation results show that the speckle noise of the reconstructed image using the proposed method is significantly suppressed compared with that using the random phase method (RPM), which demonstrates the feasibility of the proposed method.

In recent years, multicolor lasers have shown high potential for applications in many fields, such as white light source generation, biosensor or bioimaging, and optical communication, etc. Here, we use an optofluidic microbubble resonator (OFMBR) filled with a highly nonlinear liquid to obtain multicolor stimulated scatterings. By filling OFMBR with carbon disulfide and pumping it with nanosecond pulsed laser, a broadband visible supercontinuum spanning from 532 nm to 630 nm is generated due to the stimulated Raman scattering and stimulated Raman-Kerr scattering. This study opens the way towards potential application of multicolor or white light generation using optical nonlinear liquids.

In recent years, three-dimensional (3D) display technology has developed rapidly, and it is widely used in education, medical, military and other fields. 3D holographic display is regarded as the ultimate solution of 3D display. However, the lack of 3D content is one of the challenges that has been faced by 3D holographic display. The traditional method uses light-field camera and RGB-D camera to obtain 3D information of real scene, which has the problems of high-system complexity and long-time consumption. Here, we proposed a 3D scene acquisition and reconstruction system based on optical axial scanning. First an electrically tunable lens (ETL) was used for high-speed focus shift (up to 2.5 ms). A CCD camera was synchronized with the ETL to acquire multi-focused image sequence of real scene. Then, Tenengrad operator was used to obtain the focusing area of each multi-focused image, and the 3D image were obtained. Finally, the Computer-generated Hologram (CGH) can be obtained by the layer-based diffraction algorithm. The CGH was loaded onto the space light modulator to reconstruct the 3D holographic image. The experimental results verify the feasibility of the system. This method will expand the application of 3D holographic display in the field of education, advertising, entertainment, and other fields.

Phase technology is widely utilized in the field of optics. By applying phase technology, the required pattern can be obtained by remodeling the light field in the focal area of the objective lens, which has significant value in laser manufacturing, biomedicine and optical imaging. Gerchberg-Saxton algorithm is commonly used in imaging systems to restructure the light field, which is achieved by converting light intensity distribution of the Fourier plane optical field into the phase distribution on the focal plane through the inverse Fourier transform. Nevertheless, for a high numerical aperture objective lens, the accuracy of the relationship between the phase and the intensity of the light field may be compromised by depolarization effects, which causes the Fourier transform unable to accurately generate the required lattice pattern from the known light intensity distribution. To obtain the intensity of the light field and phase information during the optical transmission process from the rear focal plane to the front focal plane of the objective lens, we utilize the Debye diffraction in place of the Fourier transform in the Gerchberg-Saxton algorithm. Image skeletonization is a morphology-based image processing technology used to extract the backbone structure and shape information in the image, which extracts the main structure of the image and generates a more simplified representation by eliminating redundant information in the image. Image skeletonization technology has applications in many fields, including computer vision and medical image processing, among others. In this paper, we demonstrated the generation of lattice patterns from arbitrary images in the strong focusing of light field using Debye diffraction theory and image skeletonization technology.