Piston aberration in isoplanatic error does not affect imaging quality and requires no calibration; therefore, effective anisoplanatic error should eliminate piston aberration. The approach to compute the piston-removed isoplanatic angle is proposed in this study, which involves measuring double star wavefront error with Shack-Hartmann wavefront sensor. First, the value of the anisoplanatic error in various atmospheric environments is computed using Sasiela and Van Dam analytical expression for angle anisoplanatic error. Thereafter, the process of wavefront error measurement in an actual adaptive optics system with different atmospheric conditions is simulated and the anisoplanatic error is computed using phase screen method. The numerical simulation findings and theoretical calculations are similar. Meanwhile, the correspondence between wavefront error and piston-removed isoplanatic angle is computed. Finally, the anisoplanatic error of double stars is estimated and the piston-removed value of the isoplanatic angle is computed in Lijing 1.8-m astronomical telescope. The finding is confirmed using the approaches of differential image motion and stellar scintillation. The experimental findings exhibit that the piston-removed isoplanatic angle differs slowly in the temporal dimension and rapidly in the spatial dimension, and the importance of the piston-removed isoplanatic angle will be lost with long distance. Based on the approach, the correspondence between wavefront error and piston-removed isoplanatic angle in other atmospheric models and telescopes could be computed and it offers a basis for the location of the beacon.

Underwater visible light communication (UVLC) technology based on a light-emitting diode is a type of underwater wireless communication approach that simultaneously realizes the functions of illumination and communication. UVLC can effectively solve many disadvantages of underwater acoustic communication, such as large delay, small bandwidth, and high energy consumption. However, it reduces the signal-to-noise ratio (SNR) of the receiving plane due to the attenuation of light propagation caused via various media in seawater, degrading the communication quality of the system. Additionally, the concentration of the underwater medium changes as the depth varies, causing the change in the light propagation absorption and scattering coefficient, which affects the parameter setting of the error-correcting coding. In this paper, we use the Monte Carlo approach to implement vertical UVLC channel modeling by operating on the Matlab simulation platform to obtain SNR that contributes to the design of an error-correcting coding scheme based on the polar codes, ensuring that the data transmission is reliable at different channel conditions by adjusting coding parameters. The simulation result shows that the proposed scheme can achieve error-free transmission at different SNRs by adjusting the code rate. Therefore, the proposed scheme can ensure the reliability of the UVLC system by adjusting the coding parameters obtained from the actual channel environment.

The optical nondestructive extraction of fingermarks plays an important role in investigating and solving cases. Paper is a common carrier in various cases, which is a permeable object under most situations, and extracting potential oil fingermarks from it is difficult. This study explores the optical nondestructive extraction method of potential oil fingermarks on various paper types through experiments. A total of 7 kinds of paper in three categories of smooth, semi-smooth, and rough textures are selected as trace carriers, and a total of 6 kinds of oil fingerprints in four categories of oil, vegetable, mineral, and essential oils are selected as detection materials. Optical inspection of 42 samples is conducted based on a full-band CCD photographic system, and the extraction results are compared with those obtained under natural light. The experimental results show that the extraction effect of the 254 nm short-wave ultraviolet reflectance photographic is superior to that of natural light. However, their fingerprint extraction results differ because of the differences in the reflection properties of the marks bearing objects and oil. The conclusion provides basic data for fingermark extraction on site.

In the disciplines of focal field modulation, optical micro-machining, optical micromanipulation, and optical communication, the new optical field modulation technology has made significant achievements. In this study, we propose a composite light field modulation scheme based on the Bessel beam that realizes a distant super-diffraction limiting focus using the Bessel beam’s intrinsic angle spectrum and the annular aperture’s sharp edge diffraction. The theoretical and experimental results reveal that the bottle beam formed using the axicon-lens system has a focusing property and that the high-frequency components can be enhanced using the annular aperture’s sharp edge diffraction, resulting in super-diffraction properties bottle beam. The local focused light field is separated from the surrounding side lobe light field and is expected to be applied in far-field super-resolution microscopic imaging and optical tweezers.

In high precision laser ranging, simulation of intersatellite ultra-long distance propagation plays a crucial role. The lasers’ propagation distance between satellites takes hundreds to millions of kilometers; due to wavefront aberration and the diffraction effect in the detection approach, the lasers’ propagation cannot be directly simulated using the classical Gaussian beam tracing approach. A mode expansion method is used in this study to simulate the ultra-long distance intersatellite diffraction propagation. The simulation accuracy is confirmed by comparing with the analytical approaches and Fraunhofer diffraction integral. The mode order influence and ratio of the initial Gaussian beam waist radius to the aperture radius on the simulation accuracy are examined. Thus, this numerical simulation approach with both computation accuracy and efficiency is offered for the high precision simulation laser ranging in space.

In this paper, the performance of microwave photonic link is analyzed based on Taylor series expansion method. In order to improve the accuracy of theoretical analysis of microwave photonic link, this method analyzes the application range of Taylor series expansion method based on the Taylor series and the modulation coefficient. The results show that when the modulation coefficient m is in the range of 0-1.74, the average peak value calculated by Bessel function expansion method is 5-6 dB higher than the experimental data, while the average peak value calculated by Taylor series expansion method is 1-2 dB higher than the experimental data, which is closer to the theoretical calculation results.

To examine the monitoring performance of optical frequency domain reflectometry (OFDR) and ultra-weak fiber Bragg grating (UWFBG) technologies in the bridge steel structure, this study focuses on the bending measurement experiments of H-shaped steel beam. Four optical fibers are arranged along the full length of the steel beam and distributed strain measurement investigations are performed under heavy and light load conditions for the four-point loaded bending deformation of the steel beam. The findings reveal that both OFDR and UWFBG technologies indicate remarkable monitoring performance in the distributed strain measurement of the steel beam. Compared with the findings of the strain gage, the average measurement errors of the OFDR technology and UWFBG technology under heavy load conditions are within 3 με and 2 με and under light load conditions are within 2 με and 1 με, respectively. The test findings for the 0.9 mm tight-buffered fiber and the bare fiber are similar, demonstrating that the tight-buffered fiber does not minimize the fiber's strain transmissibility. In addition, the spatial resolution of UWFBG measurement findings can be enhanced through experimental design, and the degree of improvement depends on the grating density of the laid fibers and relative grating spacing between adjacent fibers.

In this paper, the rigid polyvinyl chloride material support and hanger structural pipeline is modeled by finite element analysis software, and the mechanical simulation is carried out by applying a static continuous load vertically downward from the center. Sensing fibers are arranged in a straight line along the axial direction on the top, bottom, and sides of the simulated pipe, the strain on the outer surface of the pipe is transferred to the sensing fiber by sticking the sensor, and the Brillouin optical time-domain analyzer is used to monitor the strain change of the pipeline under different loads. The results show that the axial direction of the pipeline to the bottom and top are tensile positive and compressive negative strains, respectively, and the strain of the side midline is unchanged. Moreover, the strain in the middle of the pipeline is the largest, whereas that towards the two ends of the pipeline gradually decreases, and the strain at 0.6 m tends to 0. Additionally, the strain sensitivity at the bottom of the middle section of the oil and gas pipeline is 3.3 and 5.5 times that at the top and support end, respectively.

Because optical frequency combs with a large number of comb lines and high flatness are difficult to generate and the channelization efficiency of them is low, a microwave photonic channelized receiver based on signal polarization multiplexing is proposed. By using two 2-line local optical frequency combs with different frequencies to demodulate the radio frequency signal in the orthogonal polarization state, 16 subchannels with a bandwidth of 1 GHz can be received simultaneously. Experimental results show that the image rejection ratio and the third-order spurious-free dynamic range of the system can reach 24 dB and 95.2 dB·Hz2∕3, respectively. The proposed receiver can simultaneously receive a large number of subchannels and have a high channelization efficiency; thus, it has great application potential in broadband wireless communication, radar, and electronic warfare systems.

When the bearing has various faults, the vibration signal's variance distribution in various frequency bands is not balanced. In order to extract the features of various fault signals efficiently and for the frequency components generated from the bearing fault signal's wavelet packet decomposition, this study proposed a variance equalization method of nonlinear equalization. The higher discrimination degree of fault characteristics can In order to extract the features of various fault signals efficiently and for the frequency components generated from the bearing fault signal's wavelet packet decomposition, this study proposes a variance equalization method of nonlinear equalization. The higher discrimination degree of fault characteristics can be achieved. Based on the data from Case Western Reserve University's bearing data center's collected bearing vibration in the experiment, the variance parameters extracted from a normal, inner ring fault, outer ring fault, and rolling element fault bearing signal under four speeds are investigated using this approach. The results reveal that the variance parameters of various fault signals after equalization have better discrimination. It can efficiently differentiate the types of bearing faults.

This paper proposes a digital holographic phase demodulation approach based on the transport intensity equation (TIE), which is solved with a discrete cosine transform. Simulative and experimental findings reveal that the new approach successfully accelerates the unwrapping process with no loss of accuracy compared with the traditional approach based on fast Fourier transform. The new approaches' efficiency can still be enhanced after choosing a suitable extending scheme for the computation of the axis derivative of intensity. The proposed new TIE-based phase unwrapping approaches can lead to the real-time uses of the phase measurement with high processing speed and precision.

In this paper we report a compact and robust regenerative amplifier developed as the pump laser for a high repetition rate terahertz parametric amplifier. With properly chosen pump source and carefully designed cavity, Nd∶YVO4 crystal, and laser beam collimator, a maximum output pulse energy of 480 μJ has been achieved at the repetition rate of 10 kHz. The output laser has a nearly Gaussian transverse profile and a narrow bandwidth of 0.2 nm. Long-term monitoring shows an root mean square power fluctuation of about 1%. These characteristics satisfy all requirements for high repetition rate terahertz parametric amplifier.

The 0-2π vortex phase plate is introduced to measure the phase retardance of the wave plate. By constructing a functional relationship between the phase delay of the wave plate and the azimuth angle of the hollow elliptical spot of the emitted light, the phase delay is simulated and calculated. Furthermore, the demonstration and analysis of the wave plate test method are realized. Theoretically, the measurement range of the phase retardance of the wave plate is expanded to 270°, and the theoretical measurement error does not exceed ±0.71%.

Based on the working characteristics of the pulsed laser diode (LD) end-pumped composite crystal, a finite element thermal model of the pulsed LD pumped YAG/Nd∶YAG composite crystal was established using the heat conduction theory to solve the thermal effect caused by the LD end-pumped crystal. The effects of pump power, undoped crystal thickness, and pulse width on the temperature field and thermal deformation of the composite crystal were quantitatively analyzed. The results show that when the thickness of the doped crystal is 8 mm, the thickness of the undoped crystal, pulse width, and repetition rate is 3 mm, 3 ms, and 100 Hz, respectively. Furthermore, the radius of the pump spot collimated and focused by the optical coupling system is 300 μm when a pulse with a pump power of 80 W is applied. In the LD end-face pumped composite crystal YAG/Nd∶YAG, the highest temperature and maximum thermal deformation available at the center of the end-face pumped are 66.84 ℃ and 0.12 μm, respectively. It is thought that the composite crystal can effectively reduce the high-temperature rise of the crystal and the thermal deformation of the end-face of the crystal. This conclusion provides theoretical guidance for realizing the high power output of a Nd∶YAG laser.

The experiment employs 45 steel and Fe45 as the base material and cladding powder, respectively, to develop three factors and five levels of the test scheme, and evaluate the cladding layer's macroscopic size, to solve the challenge that the cladding layer morphology is difficult to control in a laser cladding process, First, the backpropagation (BP) neural network's initial value was optimized using a genetic algorithm (GA), and GA-BP neural network model was developed. The laser process parameters were taken as input and cladding layer morphology as output to train and test, and the prediction accuracy was examined. Second, the prediction model was developed using regression analysis, BP neural network, and GA-BP neural network, and compared with the actual cladding layer morphology. The findings demonstrate that the GA-BP neural network model's error optimized by the genetic algorithm was about 3%, the maximum error of the BP neural network prediction model was 7.38%, and the maximum error of the regression analysis prediction model is 15.5%. It can be seen from the comparison that the results of the GA-BP neural network prediction model are the closest to the actual. Thus, the GA-BP neural network prediction model has a certain regulating value for enhancing the quality of the cladding layer.

In order to explore the comprehensive characteristics of the linewidth of the lasers, the theoretical analysis of the linewidth of the wavelength-tunable narrow linewidth lasers is carried out. In this paper, the delayed self-heterodyne measurement system based on the non-equilibrium Mach-Zehnder interferometer structure is built to investigate the steady-state and dynamic linewidth characteristics of wavelength-tunable narrow linewidth lasers. In order to balance the speed and accuracy of linewidth measurements, linewidth tests at different receiver bandwidths are implemented. For the linewidth spreading problem arising from continuous laser wavelength tuning, the linewidth measurement error is compensated by controlling the stepping amount while maintain the stability of the output power. This study can not only improve the study of laser linewidth characteristics, but also has important significance for the study of optical frequency-domain reflectometry technology.

High-power free space chaotic laser is generated by a 1530 nm wide-ridged high-power semiconductor lasers (SL) with optical feedback. The multi-transverse-mode output beam result in the suppression of time-delay signature (TDS), eliminating the TDS's interference on the chaotic laser ranging. As the SL drive current increases, the TDS is gradually suppressed, but the relaxation oscillation signature is suppressed only in some current range. The current range and corresponding output laser power at different transmission/reflection ratios of beam splitter are investigated in detail. A chaotic laser with average power of 440 mW, the autocorrelation main peak half-height width of 0.07 ns, and the peak side lobe level of -6.3 dB is generated. This paper provides a chaotic laser source with simple structure, low cost, and high performance for chaotic laser ranging.

Laser welding is the key technology of new energy battery manufacturing. To ensure the full absorption of pump light and laser light conversion efficiency, 976 nm semiconductor laser pump technology is used, and the length of gain fiber is shortened to increase the laser stimulated Raman scattering threshold. And a novel gain fiber coiling method is provided to suppress the mode instability and improve the output beam quality. The output power of single-mode (M2≤1.1) laser is 2.25 kW, the Raman suppression ratio reaches -38 dB, and the length of energy transmission fiber (14 μm core diameter, numerical aperture is 0.07) reaches 7 m. The output laser has high brightness, small spot diameter, and high power density, which can effectively reduce the thermal effect during welding and avoids weld defects and spatters.

High-strength aluminum alloys are widely used in the aerospace industry owing to their excellent specific strength and plasticity. Additive manufacturing technology, which has developed rapidly in recent years, provides a new method for preparing high-strength aluminum alloys. Here, the Al-Mg-Sc-Zr alloy is prepared using selective laser melting (SLM). The microstructure and mechanical properties of the alloy are characterized and studied by X-ray computed tomography, optical microscope, scanning electron microscope, electron backscatter diffraction (EBSD), and a tensile test at room temperature. The results indicate that the forming quality of the Al-Mg-Sc-Zr alloy formed by SLM is good, the porosity is only 0.0013%, and the maximum pore size is 126 μm. The microstructure of the alloy comprises coarse- and fine-grained regions: the inside of the melt pool is a coarse-grained region, while the boundary of the melt pool is a fine-grained region. The Al3(Sc,Zr) particles at the boundary of the melt pool provide numerous nucleation sites for the precipitation of Al grains, resulting in a remarkable grain refinement effect. The average grain size is 3 μm, and the average grain size in the fine-grained region is only 0.6 μm under the smaller scanning step of EBSD. The Al-Mg-Sc-Zr alloy formed by SLM has excellent tensile properties and low anisotropy. The tensile strength of the horizontal specimen is slightly higher, and its yield strength, tensile strength, and elongation rate reach 465 MPa, 508.2 MPa, and 14.07%, respectively. The characteristic of rapid cooling of SLM and the Sc and Zr elements enables the Al-Mg-Sc-Zr alloy formed by SLM to have good forming quality, refined grain structure, and nanosized Al3(Sc,Zr) particles. The resulting fine grain strengthening and precipitation strengthening are the main strengthening mechanisms of the alloy's tensile properties.

Small layer thickness is commonly used for printing in the selective laser melting (SLM) process to improve the forming quality of the parts. However, it has a negative impact on production efficiency and is not commercially viable. To solve the contradiction between good forming quality and high SLM production efficiency, 316L stainless steel specimens with different powder layer thicknesses were prepared using optimizing process parameters. The technological parameter of the relative density, roughness, mechanical properties, and microstructure of the formed parts was studied under different powder layer thicknesses. When the forming conditions of three layer thicknesses (30 μm, 45 μm, and 60 μm) are compared, it is discovered that the layer thickness has little effect on the relative density of SLM samples under the optimized process window condition. Moreover, the relative density can reach more than 99.90% under different powder layer thicknesses, and there are no obvious defects in the microstructure. The dimensional accuracy, surface roughness, and mechanical properties of the samples are mainly affected by the layer thickness. The tensile strength gradually increases as the layer thickness increases, while the dimensional accuracy and roughness decrease. The forming efficiency of 60 μm powder thickness is increased by 35. 71% compared with 30 μm powder thickness.

It is proposed to grow VO2 nanoparticles on the surface of porous silicon using a chemical vapor transport deposition method to form a porous silicon-based VO2 nanoparticles composite structure for improving the sensitivity of porous silicon to NO2 gas at room temperature. The size of VO2 nanoparticles is altered by varying the VO2 deposition pressure and research is conducted on its effect on the gas sensitivity of the porous silicon-based VO2 nanoparticle composite structure at room temperature. The microscopic morphology, phase, and crystal structure of the composite structure are characterized and analyzed using a field emission scanning electron microscope, X-ray diffractometer, energy spectrometer, and transmission electron microscope. The experimental results demonstrate that the composite structure obtained at the deposition pressure of 330 Pa has the highest room temperature sensitivity (13.15) to the mole fraction of 5×10-6 NO2, which is 5.95 times the sensitivity of porous silicon, and has good selectivity. The excellent NO2 gas sensitivity is due to the surface activity enhancement of VO2 nanoparticles with small particle size and the formation of a wider depletion layer between the smaller VO2 nanoparticles and porous silicon, thus improving gas sensitivity. This research will help to improve the application of porous silicon in NO2 gas sensor.

This study begins from the tunnel lighting's brightness uniformity, which takes the evaluation standard of detailed rules for highway tunnel lighting design as the constraint condition, and a light distribution model of lamps based on tunnel structural parameters is created using the point by point approach. The simulation tunnel scene is constructed using DIALUX, the tunnel structure parameters are brought into the lamplight distribution model, and a suitable lamp light distribution curve is computed, the designed lamps' lighting performance is confirmed using experiments. The findings demonstrated that the lighting fixtures created with this model can guarantee the tunnel environment's average illuminance, average brightness, brightness uniformity, and longitudinal brightness uniformity match the national evaluation standards. Furthermore, the lighting quality is compared and examined by adjusting numerous tunnel parameters in the experiment (light distribution mode, lamps' installation elevation, and installation spacing), and it is concluded that the designed lamps provide the best lighting quality and energy savings under the initial tunnel parameters. The efficiency of the tunnel lamps light distribution model is confirmed and demonstrates that the model has good application and popularization value in the tunnel lamp design field.

We propose a surface plasmon metal-insulator-metal (MIM) waveguide structure comprising a H-type resonator and an independent branch. The Fano resonance and optical sensing characteristics of the structure are examined by using finite element analysis. The findings reveal that the structure can achieve Fano resonance, and the maximum refractive index sensitivity and quality factor are 1078.33 nm/RIU and 1259.2, respectively. The effects of structural geometric factors on Fano resonance are examined, and independent changes of the Fano resonance line and wavelength are obtained. The suggested plasmonic MIM waveguide structure in this work has potential applications in integrated photonic devices and nanooptical sensors.

Photodetectors operating in the visible and near-infrared bands are an indispensable part of various applications, such as optical communications, deep space exploration, and biomedical imaging. We introduce metal nanostructures on a thin layer of graphene to improve the performance of photodetectors. We use COMSOL to establish multiple sets of models for simulation comparison. The results show that at a period (P) of 250 nm and particle diameter (D) of 112.5 nm, the addition of pyramid nano-metal particles and a triangular cross-section grating enhances the light absorption of the graphene photodetector in the visible and near-infrared bands. In the wavelength range of 0.5-5 μm, the nanoparticle grating structure can further improve the absorption performance of the device. The results indicate that particle coverage is the key factor affecting the light absorption efficiency.

Important information such as amplitude, frequency, phase and polarization was encoded in the interference pattern. One important phenomenon that has not been studied in detail is the interference of two Gaussian beams with any polarization state. It is necessary to find a relation between polarization of light and interference pattern. In this paper, a fiber Mach-Zehnder interferometer was used to produce light with spatially varying polarization. A general expression for the light intensity distribution is derived for interference of two Gaussian beams with arbitrary polarization. The theory is validated by experiment. The research shows that various interference patterns can be generated as the polarization is changed. Two Gaussian beams with the same polarization states can interfere and clear interference fringes were observed. Two Gaussian beams with orthogonal polarizations can not interfere and no interference fringes are observed. In other cases, the fringe contrast varies between 0 and 1. This study is very helpful in understanding and applying the interference of polarized light.

The losses during the preparation, propagation, and detection of photons greatly limit the quantum computing advantages of Boson sampling. Boson sampling simulations with four photons and eight modes are realized based on the Clements model using the Markov chain Monte Carlo (MCMC) method to study the influence of photon losses on Boson sampling results in optical networks, and the simulation results are validated and distinguished from the Boson sampling with photon losses at the photon source using the Bayesian test method. The simulation results show that by introducing photon losses based on the optical network, the sampling results obtained using the MCMC method can effectively satisfy the Bayesian test. The number of samples required to satisfy the Bayesian test decreases gradually and tends to be stable when the interval of samples increases. Conversely, as the scale of the optical network increases, the MCMC method requires a larger interval of samples to quickly satisfy the Bayesian test. In this study, Boson sampling with photon losses in optical networks is successfully simulated using MCMC method, giving a clue for Boson sampling researches while considering the errors.

Fiber optic distributed acoustic sensing (DAS) based on phase sensitive time domain reflectometry can realize large-scale distributed acoustic detection, which has attracted the research attention in many application fields in recent years, such as oil and gas exploration, geological imaging, pipeline safety and perimeter security. In this paper, the sensing principle of fiber optic DAS is discussed, and the fading mechanism and performance bottleneck of single mode fiber DAS are analyzed. To solve these problems, the acoustic sensing mechanisms and performances of various scattering enhanced fibers are introduced. Furthermore, the recent technologies and applications of the microstructured scattering enhanced optical fiber-based DAS system are briefly reviewed, and the possible development directions of DAS technology in the future is prospected.

The mid-infrared 2 μm band solid-state laser has a wide range of applications in the fields of industry, military, medical, and scientific research. Single-doped holmium solid-state laser is an important method to produce 2 μm lasers. 2 μm lasers can also provide an effective pump source for mid-infrared optical parametric oscillator. This paper introduces the advantages of single-doped holmium solid-state laser, and summarizes the research progress of single-doped holmium solid-state lasers based on various substrates in the past decades. Finally, the future development prospect of single-doped holmium solid-state lasers is prospected.

One of the most important components of an infrared optical system is the infrared optical element. Owing to its wide transmission band, good achromatic and athermalization performance, and abundant raw materials, chalcogenide glass is an excellent infrared optical material. It has broad application prospects in the infrared field. However, when compared to other infrared optical materials, chalcogenide glass has a high thermal expansion coefficient and a low softening point temperature, making surface coating and film deposition difficult. In this paper, the surface processing and coating methods of the waiting-to-be coated chalcogenide glass surface are introduced, and the methods and research progress of depositing anti-reflection and protective coating on the surface of chalcogenide glass elements are reviewed. In addition, the current situation and existing problems of the surface processing and coating of the waiting-to-be coated chalcogenide glass surface, as well as the development trend of its optical surface preparation and cohesion are summarized.

Photon detection technology plays an important role in high-energy physics, astrophysics, medical imaging and other disciplines. Especially in radiation detection applications, it has been the ultimate goal of photodetector development in recent decades to achieve high-level sensitive detection of single photons. Silicon photomultiplier (SiPM) technology is an unprecedented attempt in the field of ideal solid-state photon detectors. With its excellent performance (high gain, low bias voltage, fast time response, magnetic field insensitivity, etc.), SiPM technology is attracting more and more researchers' attention. Focusing on the structure principle of SiPM, this paper reviews, classifies and summarizes the research progress of SiPM in the aspects of structure, performance and application in recent years.

The most mature and widely used method for describing the scattering characteristics of a target surface is to use the bidirectional reflection distribution function (BRDF). However, the key is how to quickly and accurately obtain BRDF characteristic parameters. In this study, the Cook-Torrance model is employed to model the scattering from a target surface, the black coating metal is detected using a 1550 nm laser, and the measured data are inversed using a genetic tabu search algorithm to obtain the unknown parameters in the model. Compared with the genetic algorithm and genetic simulated annealing algorithm, the algorithm optimizes the number of iterations, reduces the computation error, and obtains a theoretical value that matches the experimental value. This study offers a quick and accurate approach to calculating the unknown parameters in BRDF.

In this paper, a particle size measurement method based on continuous transmission extinction spectral is proposed. Based on Mie scattering theory and artificial bee colony algorithm for particle size inversion. The results show that the relative root-mean-square error (RRMSE) of particle volume frequency distribution curve is as low as 0.08% for unimodal distribution, and the RRMSE of particle volume frequency distribution curve is as low as 3.49% for bimodal distribution. Comparative experiments are conducted with the standard polystyrene latex particles numbered GBW120134, GBW120024 and GBW120041. The results show that the relative error of D50 particle size is within 10% for unimodal distribution, and the relative error of D50 particle size is within 20% for bimodal distribution.

Glucose concentration measurement is crucial in various fields, including biology and medicine. This study proposes an orthogonal mirror to eliminate the 180° flipping of the polarization that generally occurs following single reflections from a metallic mirror to enhance the resolution of the polarimetry for measuring glucose concentration. The relationship between the solution concentration and the phase difference of reference light and measurement light is established. Furthermore, the effect of multiple polarization rotation based on the orthogonal mirror is explored. Multiple polarization rotation increases the glucose concentration measurement resolution without increasing the sample length. Taking glucose solution as an example, the experimental results of four rotations demonstrate that the concentration measurement resolution is 8×10-6 g/mL in the range of 0-0.4690 g/mL with a maximum relative error of less than 0.54%. The proposed approach can be used for online and real-time glucose concentration detection for research on glucose abnormalities in the pathogenesis of autism spectrum disorders.

In this work, novel fluorescent carbon dots were prepared via the microwave method utilizing cortex magnoliae officinalis as a carbon source. The size, morphology, and elemental composition of the fluorescent carbon dots were characterized using transmission electron microscopy and X-ray photoelectron spectroscopy. Optical properties of the carbon dots were also characterized based on fluorescence and absorption spectra. Considering the fluorescent quenching of the carbon dots, a new method was developed for the detection of 2, 4, 6-trinitrophenol using the carbon dots as a fluorescent probe. Experimental results reveal that the average diameter of the fluorescent carbon dots is 5 nm, and the main components are carbon and oxygen. Further, the maximum absorption wavelength is 280 nm, and the maximum excitation wavelength is 320 nm; notably, a quantum yield of 0.14 is achieved. Under optimal experimental conditions, the logarithm of the ratio of the fluorescent intensities without and with samples and the concentration of 2, 4, 6-trinitrophenol exhibits a good linear relationship, with a linear range of 0.8-80 μmol/L. Further, the limit of detection is 160 nmol/L. Those results are expected to facilitate the rapid, sensitive, and efficient detection of 2, 4, 6-trinitrophenol in authentic samples.

Finite-difference time-domain (FDTD) methods often require smaller spatial discrete steps when calculating the nonlocal properties of metal nanostructures, which brings difficulties to the calculation when the model size is large. However, due to the introduction of longitudinal wave vector, the hydrodynamic model describing the properties of the metal nonlocal property is inconvenient for the calculation of semi-analytical methods such as the transfer matrix method (TMM). Therefore, a method combining FDTD and TMM to solve the absorptivity of nano-metal nonlocal thin films is proposed in this paper. The reflection coefficient and transmission coefficient of the metal are obtained by the FDTD method, and the equivalent dielectric constant of the nonlocal metal is obtained by inversion. Substitute the equivalent permittivity and model parameters into the TMM, and the electromagnetic properties of the complete structure are calculated. The results show that this method can solve the problem of insufficient memory caused by small grid of FDTD and the computational complexity caused by longitudinal wave vector in TMM, and calculations of reflectivity, transmittance, and absorptivity of layered nanostructures can be performed quickly.

As an important means of high-temperature protection for aero-engine turbine blades, the quality of aluminized coatings is closely related to flight safety. The thickness of the aluminized layer is an essential factor in evaluating its performance. However, it is not easy to measure it accurately by current nondestructive testing methods. For this problem, the X-ray fluorescence technology is combined with the extreme gradient boosting (XGBoost) algorithm, and the feature element extraction by Pearson correlation coefficient screening (PCCS) is used to build a prediction model for the thickness of the aluminized layer. The average relative error of the prediction results is compared with K nearest neighbor regression, linear regression, support vector machine, and random forest models. The results show that the PCCS-XGBoost model had the smallest average error of 1.60% in predicting thickness compared with other models. The study provides a new prediction method for nondestructive testing of the thickness of the aluminized layer.