To further study the application of Gaussian laser beams in underwater communication and information detection and the characteristics of the transmission process in different seawater environments, in this study, the most-common terrestrial suspended sediment particles in seawater were taken as an example. First, Mie scattering theory was combined with the Monte Carlo method to establish a 520-nm Gaussian laser transmission model in seawater containing suspended solids, and the effects of particle groups with specific diameters and densities on laser transmission were studied. Second, the variation in the normalized received power with the initial divergence angle of the laser at different detection distances was analyzed. The research results indicate the following. 1) When the diameter and density of suspended sediment particles in the Mie scattering model are changed, thereby changing the extinction coefficient, scattering coefficient, and asymmetry factor set in the simulation, the received power of the detection target decreases exponentially with increases in scatterer diameter, density, and transmission distance. 2) Within a certain range, the change in the initial divergence angle does not affect the power of the receiving surface, and this range decreases with increases in the scattering coefficient and transmission distance. The research method used lays a theoretical foundation for further analyzing the changes in Gaussian laser transmission characteristics in seawater containing complex particle groups (suspended bubbles, planktonic algae, and suspended sediment) and provides reference for related engineering estimates.

This study aimed to assess the transmission and communication characteristics of an helical Ince-Gaussian (HIG) beams in ocean turbulence channels. First, the relationship between the transmission performance (intensity distribution, phase distribution, scintillation index, centroid drift, and overlap) and the transmission distances of an HIG beams passing through ocean turbulence was simulated based on the random phase screens and the power spectrum inversion method. Next, communication bit error rate was analyzed based on the log-normal intensity probability density function. Further, the performance of the HIG beams under different beam parameters (ellipticity, order, and degree) was analyzed and optimized to achieve optimal transmission and communication performance. The simulation results revealed that the HIG beams exhibit better anti-turbulence ability at different distances compared to the Gaussian beam. In a 100 m ocean turbulence channel (ε = 10-5 m2∕s3, XT = 10-5 K2∕s, ω = -0.15, η = 10-3 m, L0 = 10 m), the scintillation index, the centroid drift and the bit error rate were reduced by 58%, 53%, and 3 orders of magnitude, respectively. Further, the transmission and communication performance of the HIG beams decreased with the increase in turbulence intensity, and the performance improvement ability of the HIG beams also decreased compared with the Gaussian beam. The bit error rate improved by about 4 orders of magnitude under relatively weak turbulence, while it improved by about 1 order of magnitude under relatively strong turbulence. When the outer scale of ocean turbulence increased, the centroid drift of the HIG beams increased slightly, while the other parameters were almost unaffected. After optimization, ellipticity, order, and degree can improve the communication and transmission performance of HIG beams,and the order is the most sensitive parameter. The simulation results may provide a theoretical basis and a technical reference for the application of HIG beams in underwater optical communications.

Spatial optical couplings in atmospheric turbulence channels are associated with low efficiencies and difficult alignments, hence, in this study, a research scheme for coupling a turbulent signal beam into optical waveguides through a grating was proposed and the influence of atmospheric turbulence on spatial light and optical waveguide coupling parameters was analyzed. Moreover, a highly efficient spatial optical coupling waveguide chip was designed by optimizing the structural parameters of the grating. Additionally, three sets of Si/SiO2 mirrors were introduced to reduce the downward coupling loss and further improve the grating coupling efficiency. Simulation results show that for the spatial light affected by atmospheric turbulence, the coupling efficiency of the incident grating coupler at 1550 nm was 74% (50.5%, without adding the mirrors) when the grating period, etching depth, and lower cladding thickness were 660 nm, 100 nm, and 1.45 μm, respectively, indicating the efficient coupling of spatial light in the atmospheric turbulent channels. The findings of this study will be of great significance in improving the communication efficiency and photoelectric integration in the field of free-space optical communication.

In order to improve the accuracy of ocean-land waveform classifications of airborne green lasers in complex ocean-land environments, an ocean-land waveform classification method based on multichannel weighted voting [i.e., multichannel weighted voting convolutional neural network (MWV-CNN)] is proposed. First, the multichannel green laser waveforms collected in the deep and shallow channels are input into the proposed one-dimensional convolutional neural network (1D CNN) module through a multichannel input module. Second, each 1D CNN module processes each channel waveform separately to obtain the predicted scores for each channel waveform belonging to the ocean and land categories. Finally, the predicted score of each channel is treated as weight, and a multichannel fusion module is used to determine the final waveform category via weighted voting. The measured data in the coastal waters of Lianyungang, China are verified by experiment using Optech CZMIL. The results indicate that the overall classification accuracy, Kappa coefficient, and overall accuracy standard deviation of MWV-CNN are 99.45%, 0.982, and 0.02%, respectively, and as compared with traditional ocean-land waveform classification methods, the proposed method exhibits better classification accuracy and robustness, thus providing a new effective way for realizing ocean-land waveform classification of airborne green laser with high accuracy.

This study presents a high-gain broadband balanced homodyne detector, utilizing cascade amplification to generate continuous-variable quantum random numbers. The innovative approach of distributed parameter circuit analysis and optimization simulation is introduced into the circuit design of the broadband balanced homodyne detector. The objective is to enhance the transmission attributes of the ultra-high-frequency circuit. This is realized by optimally combining different elements and selecting key electronic components, guided by system stability indicators. Hence, a balanced homodyne detector was developed with a bandwidth surpassing 1.65 GHz and gain flatness of ±2 dB within the 0.2?930 MHz range. This study proposes a novel design perspective for broadband balanced homodyne detectors. The enhanced features of the detectors facilitate a more efficient derivation of continuous-variable quantum state random entropy sources, thereby propelling the rate enhancement and practical advancement of continuous-variable quantum random number generators.

The PbSe quantum dot-doped ring-core fiber is successfully prepared using a modified chemical vapor deposition method. The fiber has a double-clad structure, with a refractive index difference of approximately 2.2% between the ring core and the inner cladding. The types and contents of elements in the fiber are verified via electron probe microanalysis. The crystal structure of PbSe quantum dots is examined using a high-resolution transmission electron microscope, and the Raman spectrum is measured. The results proved that PbSe quantum dots were doped successfully into the ring-core fiber. This provides an important reference value for preparing semiconductor quantum dot-doped fiber. The PbSe quantum dot-doped ring-core fiber is the foundation for the vortex mode amplification system. The first- to third-order vortex amplifying modes are realized at 1550 nm. When the pump power is 634 mW, the on-off gains of all modes are greater than 13 dB, and the differential mode gains are less than 2.45 dB. This experimental system is expected to promote further research on vortex mode broadband amplification.

A graphene-based reconfigurable microstrip array antenna suitable for the terahertz band was designed in this study. The design combined the unique advantages of grapheme for impedance matching and electrical controllability in the terahertz band and the characteristics of high radiation efficiency of the reconfigurable microstrip array antenna. The array antenna unit embedded a graphene patch in the radiant patch as a switch and changed the switch's on-off and off-off states by adjusting the applied bias voltage of graphene. The antenna unit and the array antenna have an operating frequency of 5.012 THz. The antenna unit exhibits strong gain characteristics and anti-interference performance, and can realize the pattern of adjustment to 12°?24° at the working frequency. The 2×2 microstrip array antenna composed of the antenna unit can realize the pattern reconfiguration function of 0°?13°. The simulation results show that the maximum gain of the array antenna is 12.5 dBi and the maximum beam width is 51.4°. In addition, the array antenna exhibits good directivity and anti-interference ability.

High precision inter-satellite velocity measurement technology is one of the key technologies for realizing integration of satellite laser communication measurements and autonomous navigation. We propose an inter-satellite coherent optical communication link velocity measurement method based on modulated code element Doppler measurement. The method adopts a one-way unidirectional approach to obtain phase-continuous code element Doppler signals by using the phase and symbol information of code element symbol synchronization and verdict at the receiver side and by removing the phase modulation information in the baseband sampling data. This can aid in realizing the real-time high accuracy of satellite relative motion velocity while completing inter-satellite communication. The simulation results verify that this method can achieve the relative velocity measurement from 0 to 11.625 km/s at a communication rate of 1 Gbit/s and bit error rate (BER) of 10-9. Furthermore, the velocity measurement uncertainty exceeds 10.00 mm/s.

A new wind turbine blade damage detection method is proposed to address the challenges surrounding imprecise positioning and the inability to monitor the turbine under operating conditions, which is a shortcoming of traditional wind turbine blade damage detection. The proposed method uses optical frequency domain reflectometry(OFDR) to measure the surface strain of the wind turbine blade. Subsequently, fast Fourier transform is taken for the strain value and its fundamental frequency amplitude is taken to obtain the blade surface strain distribution. On this basis, the position, length and width of the blade damage are calculated. According to the relationship between the strain and damage degree, the damage degree judgment formula is fitted, and the blade damage degree is identified. Based on OFDR, a cantilever beam damage detection experiment is designed to simulate the instantaneous state of the cantilever beam vibration, and the damage location is identified according to the strain distribution, which verifies the feasibility of the proposed damage identification method.

Phase-sensitive optical time-domain reflection (Φ-OTDR) technology is a distributed fiber-optic sensing technique with the advantage of high-precision vibration monitoring. It can be used to detect disturbance events in the field of perimeter security. Traditional recognition methods require the manual extraction of vibration signal features and cannot retain a time correlation, leading to information loss. To solve this problem, a disturbance event recognition method based on GAF-HorNet, which does not require a feature extraction step, is developed. A one-dimensional vibration signal is converted into a two-dimensional image through a Gramian angular field (GAF), and HorNet is used to train the model and perform recognition and classification. To verify the performance of the algorithm, four classical algorithms are selected to train the model for comparative experiments. The experimental results demonstrate that the average accuracy of the proposed algorithm is 93.56% for six types of signal: background noise, stone knocking, stone stroking, branch stroking, pulling, and climbing. Compared with previous methods, the method proposed has better recognition rate and false alarm rate performances.

A new system based on optical external modulator frequency multiplication is proposed to generate W-band linear frequency modulated (LFM) signals for high-resolution ranging. The LFM signals from the arbitrary waveform generator (AWG) are modulated to the sideband of the optical carrier through the optical modulator. The photoelectric conversion is completed in the photodetector (PD) to generate quadruple frequency W-band LFM signals, whose center frequency and bandwidth are four times the original LFM signal. This broadband LFM signal is emitted to free space for target detection. For distance measurements, the two targets are separated by 50 cm, and the measured value is 48.8 cm with an error of 1.2 cm. The distance between the two objects is set to 40 cm to demonstrate the reliability of the experiment. The measured value is 38.9 cm, and the error is 1.1 cm. The system overcomes the “electronic bottleneck” that is difficult to directly generate high-frequency signals in the electrical domain and achieves high-resolution ranging via photonics-aided generation of the broadband LFM signal. Thus, the proposed method provides a solution for future ultrahigh-resolution LFM continuous-wave radar systems.

A miniaturized, wide-band, high-sensitivity fiber Bragg grating (FBG) vibration sensor is proposed. The millimeter-scale FBG is used to design the sensor structure. The "lever hinge" structure is used as the strain transfer beam, and the center of gravity of the entire mass block is adjusted by hollowing out the end of the mass block, which improved the natural frequency of the sensor. This structure increases the natural frequency of the sensor with a slight decrease in sensitivity. In this study, a vibration sensor with a volume of 15 mm × 15 mm × 15 mm is designed to satisfy the miniaturization requirements of sensors on space cameras, and structural design and finite element simulation analysis were performed. The structural optimization of the sensor is completed, considering the working frequency band and sensitivity. The sensor is fabricated by millimeter FBG writing and sensor packaging. A vibration test system is built to test and analyze the characteristics of the sensor. The results show that the natural frequency of the sensor is approximately 1250 Hz, the sensitivity exceeds 83.3 pm·g-1 when the excitation frequency is 750 Hz, the lateral anti-interference ability of the sensor is excellent, and the cross-sensitivity is lower than 4%.

A liquid level sensor based on a single mode-peanut-seven core-peanut-single mode fiber structure is developed. The sensor uses the "peanut structure" as a fiber coupler to improve the coupling efficiency of the single-mode fiber and seven-core fiber. The first fiber "peanut structure" is used to excite the cladding mode, and the second fiber "peanut structure" couples the cladding mode with the core mode to produce interference. Because a phase difference between the cladding and core-based modes appears as they transmit through the seven-core fiber, when the liquid level of the environmental solution changes, the phase difference changes, eventually changing the transmission spectrum. In this study, the liquid level and temperature response characteristics of the sensors with seven-core fiber lengths of 24, 28, and 32 mm were experimentally studied. The experimental results show that with the increase of the liquid level, the transmission spectrum of the sensor shows a blue shift. The liquid level sensitivities of the three sensors are -0.4069, -0.2739, and -0.1653 nm/mm, and their liquid level measurement ranges are 24, 28, and 32 mm, respectively. In the water temperature range of 35?90 ℃, the transmission spectrum of the sensor shows a red shift with an increase in temperature. The temperature sensitivities of the three sensors are 0.0885, 0.0740, and 0.0879 nm/℃. The experiment shows that the sensor has the characteristics of high sensitivity, low cost, and simple fabrication, indicating that it has a good application prospect in the petrochemical industry and other fields.

Two-dimensional (2D) spatial position of a vibration source in an optical distributed acoustic sensing (DAS) system can be determined based on a phase-sensitive optical time-domain reflectometer. However, due to interference and noise, this approach may acquire inaccurate arrival time information of the first arrival wave of the vibration source at different positions of the optical cable, resulting in large positioning errors. In this study, we propose a method of estimating the first arrival wave of the vibration source in a DAS system based on bilateral filtered edge detection. First, the spatio-temporal 2D signals collected by the DAS system were converted into a gray-scale map, and then the bilateral filtering method was used to reduce the noise. The edge features in the gray-scale image were extracted using a Canny operator-based edge detection method to obtain the first arrival time of the source. The proposed method can simultaneously consider the overall temporal and spatial characteristics of spatio-temporal 2D data and improve the accuracy of low signal-to-noise ratio signal of first arrival time pickup. Results show that for low signal-to-noise ratio signals affected by interference and system noise, the average error for pickup arrival time does not exceed 3 ms, pickup accuracy is higher than that of the traditional method; the algorithm takes only 0.1 s on average, and pickup time consumption is low.

A method of infrared beam collimation adjustment based on the Moire fringe is proposed based on the Talbot image of the grating and its relationship to beam collimation under spherical wave illumination. When the grating is moving, the change in the Moire fringe direction is observed and measured by an infrared array charge-coupled device (CCD) to adjust the beam collimation. As a result, fast and convenient collimation of the infrared beam is realized. The results show that, when the grating moves, because the distance is the same, the optical path changes of 0-order and ±1-order light waves differ. The fringe shows periodic vertical axis movement and periodic contrast change, but the fringe direction remains unchanged. The fringe movement and contrast change do not affect the collimation accuracy. This method overcomes the difficulty of an invisible infrared beam and achieves simpler, faster, and more convenient collimation correction than the traditional collimation method.

With the advancements of micro and nanotechnology, the preparation and application of micro-optical components have become hot research topics. Biological compound eyes have the advantages of a large field of view, small size, and good dynamic characteristics. Hence, a microlens array, which is a commonly used bionic compound eye optical element, has a wide range of applications. Herein, an electroinkjet printing-based process is proposed to prepare a multi focal length curved microlens array to resolve the problem of out-of-focus blur caused by a mismatch between the focal length of the curved substrate and the plane image sensor. A planar multi focal length microlens array was prepared based on electrojet printing, and then the antistick treatment and inverted mold were used to obtain the lens die. Finally, a multi focal length curved microlens array with an overall radius of 6 mm was prepared via negative pressure bending and glue injection. The array has a focus range of 4.9?6.23 mm and the total direction angle is larger than 60°.

GH3536 superalloy has excellent corrosion resistance and elevated-temperature strength, and is commonly used in the manufacturing of elevated-temperature components such as combustion chambers and gas turbines. Additive and subtractive hybrid manufacturing (ASHM) technology combines the advantages of high flexibility in additive manufacturing and good surface quality in subtractive manufacturing, which is an effective way to manufacture high performance GH3536 parts. Since ASHM engages the alternating of additive manufacturing and subtractive manufacturing, it is important to determine the optimal process parameters and suitable type of tools to improve the surface quality of GH3536 parts. The samples are prepared by selective laser melting with different process parameters. The relative density of the samples are measured by precision balance to obtain the optimal parameters for GH3536. Scanning electron microscopy and electron backscattering diffraction are used to observe the microstructure of GH3536 samples with optimal parameters. The samples of ASHM are machined with three different types of tools, i.e. ball end milling, round nose milling and flat end milling. The surface morphology is studied after the machining. The results show that with the laser power of 400 W and the scanning speed of 1750 mm/s, there are no obvious defects in the samples and the relative density reaches 99.93% which are the optimal process parameters in additive manufacturing. The surface roughness of the GH3536 samples processed by the round nose milling achieves 0.211 μm. This study provides guidance to the determination of process parameters and tools' type of ASHM for GH3536 parts.

Laser interference direct writing device constructed with MEMS (microelectro mechanical systems) micromirrors has advantages such as small size, fast writing speed and simple optical path. However, it is necessary to adjust the exposure time to achieve uniform exposure effect during scanning. We introduce the optical path composition and control method of this type of laser interference direct writing device. The lookup table method is used to optimize the generated exposure pattern and exposure time parameters, reducing the pixel diameter variation from about 84% to about 6%. It solves the problem of uneven exposure time in the application of laser interference direct writing devices based on MEMS micromirrors.

According to the cleaning demand of cold rolled oil on DC04 cold rolled strip surface, we use COMSOL Multiphysics software to establish the temperature field distribution and oil stain removal process model of nanosecond pulse laser cleaning oil stain on DC04 cold rolled strip surface. The results show that when the spot radius is 80 μm and the laser energy density reaches 3.48 J/cm2, the oil can be basically removed. Then, a nanosecond pulsed laser is used to clean cold rolled oil on the surface of cold rolled strip steel. The results show that when the laser energy density exceeds 3.48 J/cm2 and the laser spot overlap rate is 50%, the oil pollution can be removed, which is consistent with the simulation results. In addition, the influence of laser spot overlap rate on laser cleaning effect is also studied. The results show that the laser energy density should be increased to 4.47 J/cm2 when the spot overlap rate is reduced to 37.5%. Therefore, nanosecond pulsed laser can effectively clean the cold rolled oil on the surface of DC04 cold rolled strip without causing obvious damage to the surface of the strip, which provides a reference for determining the process parameters of nanosecond pulsed laser to clean other kinds of materials.

By using COMSOL Multiphysics software to simulate a high-power mobile laser cleaning experimental platform with wavelength of 1064 nm, repetition rate of 20?100 kHz and power of 1000 W, visualized analysis of the laser cleaning process is carried out. The effects of the peak power density and cleaning speed on the changes of the temperature field and erosion morphology of the pollutant layer and substrate are investigated. To validate the findings, scanning electron microscope and roughness testers are utilized to study the laser cleaning effects under different peak power densities and overlapping ratios. The results show that with the increase of the laser cleaning time, the temperature variation during the laser cleaning process on the rust layer followed Gaussian distribution. The theoretical cleaning threshold and damage threshold for cleaning 45-grade steel found to be 1.9×107 W/cm2 and 10.0×107 W/cm2, respectively. Within these thresholds, the cleaning efficiency and the cleaning effect improved with an appropriate reduction of the cleaning speed as the peak power density increased. The best cleaning effect achieved with peak power density of 6.0×107 W/cm2, cleaning speed of 300 mm/s and corresponding overlap ratio of 70%. These findings are significant for enabling the industrial parameterization of kilowatt-level laser cleaning experiments.

A pair of fluorescent molecules capable of producing fluorescence resonance energy transfer (FRET) were used as donor and acceptor dyes. The polarization properties of FRET optical microfluidic lasers were investigated based on the G-quadruplex structure of deoxyribonucleic acid (DNA) molecules using a Fabry-Perot (F-P) microcavity as an optical resonance cavity. In the experiment, five solutions of DNA of varying K+ concentrations (whose molecular ends are each labeled with a pair of fluorescent dyes that can produce FRET) were studied and excited with linearly polarized pump light, and the ratio of the slope of the laser threshold curve of the acceptor in the parallel polarization direction (parallel to the pump light polarization direction) and the slope of the laser threshold curve (SER) in the vertical polarization direction (vertical to the pump light polarization direction) was used as the detection signal of the laser polarization of the acceptor. Findings indicate that as the K+ content in the DNA solution increases, the pumping threshold of the acceptor laser decreases, energy conversion efficiency improves, and the slope ratio of the acceptor laser reduces, leading to decreased polarization.

In this study, using a nonlinear-polarization-rotation (NPR) mode-locked fiber laser with positive dispersion as a testbed, the polarization characteristics of the pulse are analyzed in both complete mode-locked and composite mode-locked states. The switching from dissipative soliton (DS) and noise like pulse (NLP) can be achieved by making simple modifications to the polarization controllers (PCs). Under a fixed pump power, only adjusting the PCs can obtain a composite mode-locked state caused by the spontaneous switching of pulse states. By comparing and analyzing the polarization characteristics of the pulses in the two mode-locked states, it is observed that the synchronization of the longitudinal modes corresponds to the complete synchronization of the orthogonal polarization components. Whereas, the composite mode-locked of the longitudinal modes in partial synchronization corresponds to the partial synchronization of the orthogonal polarization components. It is proved experimentally that the orthogonal polarization component controls the synchronization between the longitudinal modes. This work is of significant importance to understanding the emergence of complex dynamics in mode-locked lasers and developing stable laser dynamics technology.

A tunable multi-wavelength Brillouin-erbium-doped random fiber laser with a half-open cavity is proposed and experimentally demonstrated. It uses the backward Rayleigh scattering in the long single-mode fiber to provide random distributed feedback, and the stimulated Brillouin scattering and erbium-doped fiber to provide laser gain. In this simple laser device, stabilized 13-order Stokes light and 5-order anti-Stokes light can be obtained. By adjusting the wavelength of Brillouin pump, the random laser wavelength tuning in the range of 1550.5?1565.5 nm is realized. In addition, the wavelength fluctuation range of 1?10 orders' Stokes light is 0?0.008 nm, and the corresponding peak power fluctuation range is 0?2.28 dB, which prove that the laser has high wavelength and power stability. The results show that the laser has the advantages of simple structure, large numbers of spectral line orders, wide tunable wavelength range and high stability, which makes it has broad application prospects in many fields, such as dense wavelength division multiplexing optical communication systems, microwave photonics, precision metrology, fiber sensing and so on.

To solve the problems of wear and corrosion failure in cold-working die steel during long-term service, Ni60 coatings with different WC contents are prepared on 12CrMoV substrate using laser cladding technology. The forming characteristics, microstructure, mechanical properties, and corrosion resistance of the coatings are characterized using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, friction and wear testing machines, and electrochemical workstations. The results indicate that the additive amount of the WC can change the solidification characteristics of the melt pool, thereby reducing the width of the coatings and increasing the depth of the coatings. When the additive amount of the WC is 30% (mass fraction), the hardness of the coating is 853 HV0.3, and the average friction coefficient is only 0.467. It has excellent mechanical properties, but the toughness of the coating decreases, leading to the formation of pores during the solidification process, which reduces the corrosion resistance of the coating. When the additive amount of the WC is 10% and 20% respectively, the size of the grain structure is refined, the grain boundary area is reduced, and it has excellent corrosion resistance. When the additive amount of the WC is 20%, the corrosion current density of the coating is only 3.65 × 10-5 A/cm2, and the mechanical properties are only slightly lower than the coating obtained with 30% WC additions. Therefore, this study explored suitable WC/Ni60 coatings for wear and corrosion environments, determined the optimal additive amount of the WC, expanded the application range of WC/Ni60 coatings in mold steel, and has guiding significance for engineering practice.

To adapt the requirements of high power and narrow pulse width of detection laser in the active detection application for the eye-safe laser, a method for improving the performance of 1550 nm pulse laser diode transmitter module using equivalent circuit model analysis is proposed. The equivalent circuit model is established based on the specific laser parameters, and the model is introduced into the pulse drive circuit of the transmitter module. The key factors affecting the output characteristics of high power, narrow pulse laser are obtained through simulation analysis. The optimized two package lasers are connected to the pulse laser transmitter module to test the output laser pulse. The measured results are consistent with the simulation results, it is proved that the equivalent circuit analysis method can be used to evaluate and optimize the performance of the laser transmitter module. Finally, the optical pulse with the maximum output power over 20 W and the pulse width less than 10 ns is obtained that realizing laser output with high power and narrow pulse.

A dense and crack free Ti-48Al-2Cr-2Nb alloy (TiAl alloy) with a height of 30 cm is prepared using laser melting deposition (LMD) method with preheating process, and the internal defects, microstructure, phase composition and mechanical properties of the alloy are studied. The micro/nano CT (computed tomography) testing results show that the density of the TiAl alloy formed after preheating is 99.996% and the number of pores is significantly less than that of the TiAl alloy formed without preheating. The microstructure of the sample is lamellar structure, metastable Weinstein structure, and feathery structure observed by optical microscopy and scanning electron microscopy. Only slight segregation of Cr and Nb elements is observed through energy spectrometer equipment. Electron back scatter diffraction experiment is conducted on the sample, and the main phase composition of the sample is γ phase, containing a small amount of α2 and B2 phase. The average kernel average misorientation (KAM) value of TiAl alloy formed after preheating is slightly higher than that of the alloy formed without preheating. In addition the hardness and tensile properties of the dense and crack free alloy are tested, the alloy has a microhardness of 350 HV0.5, a tensile strength of 497 MPa, and an elongation of 0.49%. Its tensile properties are higher than those of traditional casting TiAl alloy. Therefore, the preheating process has important guiding significance for the LMD formation of high-density and crack free TiAl alloys.

A compact, discrete path Nd:YAG Innoslab laser amplifier system with novel eight-pass arrangement is developed. An electro-optic Q-switched oscillator using Nd∶YVO4 crystal as gain medium is used as the seed laser. With a seed laser power of 2.7 W at a repetition rate of 2 kHz, the amplified laser power of more than 13 W is achieved successfully with the pulse width of 15.5 ns, and the corresponding extraction efficiency is 14.6%. The experimentally measured laser beam quality factors are less than 1.7 and 1.5 in the x and y directions, respectively. Self-lasing and amplified spontaneous emission (ASE) are not observed at the maximum pump power with discrete-path laser amplifier configuration.

In view of the incomplete coverage of the photoelectric properties of the cubic phase CsPbBr3 material under the same model, the influences of hydrostatic pressure on the structure and photoelectric properties of the material are studied in depth based on first principles. The results show that when the hydrostatic pressure increases from 0 to 7 GPa, the band gap of CsPbBr3 decreases from 1.80 eV to 0.74 eV, and the bond length of Cs—Br and Pb—Br decreases by 0.31 ? and 0.22 ?, respectively, which indicate that the coupling effect between atoms increases. The static permittivity, static refractive index and static reflectivity of CsPbBr3 increase by 10.3%, 5.0% and 12.0% under 7 GPa pressure, respectively. The transition degree and migration rate of electrons increase. When CsPbBr3 falls into the low-energy region, the pressure can reduce the edge energy of the imaginary part of the dielectric function, extinction coefficient, absorption coefficient, conductivity and loss function from 0.94 eV to 0.69 eV, the conductivity increases by 17.7% and the extinction coefficient averagely increases by 11.5%. The pressure increases the loss function by 20.6% on average when CsPbBr3 falls into the high-energy region. In addition, the pressures in the UV-Vis and near-infrared regions can increase the absorption coefficients of CsPbBr3 to 1.1 and 4.7 times of the original value, respectively, and therefore can strengthen the absorption capacity of light. These properties can expand the application of the material.

TiC nanoparticles reinforced AlMgSc composites are prepared based on selective laser melting (SLM) forming process, and the phase composition, microstructure and mechanical properties of TiC/AlMgSc composites are studied. The results show that TiC/AlMgSc composites with high density (99.73%) are obtained by using the optimized SLM forming process parameters. There is no reaction between TiC particles and AlMgSc matrix during SLM forming. TiC particles provide high-density effective nucleation points, which promote the transformation of the composite structure to equiaxed grains and grain refinement, and weaken the texture strength. After adding TiC particles, the tensile strength of the composites increased by 9.9% to 611 MPa, and the elongation decreased to 10.02%. The fracture mechanism of the composites is mainly ductile and brittle mixed fracture, and TiC clusters with a size of 3?8 μm remain on the fracture surface and adhere to the aluminum matrix.

In this study, a terahertz metamaterial filter based on laser-induced graphene (LIG) is proposed. The electrical properties of the LIG under different laser parameters are investigated, and the transmission performance of the filter is measured using terahertz time-domain spectroscopy. The transmittance of the filter is 74.2% at 0.55 THz when the period of the filter unit is 500 μm. By changing the period of the filter, the center frequency can be increased to 0.65 THz. Furthermore, the characteristic of the filter amplitude is polarization-dependent. As the angle θ between the polarization direction of the incident terahertz waves and the x-axis increases, the transmittance of the filter decreases gradually. This simple and low-cost LIG method is expected to be used to prepare various terahertz metamaterial devices, which can be applied in many fields such as terahertz sensing, detection, and communication.

Three-frequency ratio technology is important for sodium Doppler lidar to detect the temperature and wind field in the mesosphere. To realize this technology, three emitted lasers with 589 nm wavelength (f+, f0, f-) should be frequency stable, the frequency switching speed should be fast and the two frequencies (f+, f-) should be frequency locked to 630 MHz relative to the central frequency (f0). In order to meet the above technical requirements, a scheme based on optical phase-locked loop (OPLL) is proposed to realize three-frequency ratio technology. The OPLL is used to realize frequency offset locking. The frequency offset locking range is ± (200~2500) MHz, the minimum step is 200 kHz and the jitter of the beat signal is within ±50 Hz. By setting the frequency shift value and changing the polarity of the error signal, the wavelength of the slave laser is constantly changed, and the three-wavelength output is realized. The PID (proportional, integral, derivative) circuit is optimized to improve the stability of the beat signal, reduce the frequency switching time and the frequency cutting time is less than 10 ms. The experimental results show that the OPLL system can realize fast switching and locking of three frequencies and meet the technical requirements of three-frequency ratio technology.

In high-power laser applications, it is common to use reflecting mirrors for controlling the beam, such as beam expansion, redirection and wavefront correction. However, various types of reflecting mirrors in the control system will absorb some of the light energy, forming a non-uniform temperature field, which cause deformation of the reflecting mirrors and ultimately affect the quality of the reflected beams. Since the support method and temperature field jointly determine the deformation of the reflecting mirrors, it is necessary to study the optimal support method for reflecting mirrors in the design of beam control systems. Based on thermoelastic mechanics, the methods to reduce the thermal deformation of reflecting mirrors using different mirror support methods are proposed, the temperature field and deformation of the reflecting mirrors under several common support constraints are quantified and simulated. The total deformation of the mirror, the relative deformation of the spot area, and the wavefront aberration introduced by the relative deformation of the spot area are compared. The results show that the support method with a small area constraint on the back of the reflecting mirror has the smallest relative deformation, and the support method with a rigid constraint on the back of the reflecting mirror has the largest relative deformation. The relative deformation of the mirror with a rigid constraint can be effectively reduced by about 98.4%. The experimental and simulation results are very close in terms of the relative deformation of the mirror in the beam spot area, and the wavefront images are essentially identical. These results provide theoretical support for the selection and design of mirror support in beam control systems.

Underwater laser communication has significant technological advantages over traditional underwater wireless communication methods such as acoustic, long-wave, and very-long-wave communication. However, the underwater environment makes the signal spot vulnerable to deformation and flicker, thus hindering the establishment and maintenance of a reliable optical link. To overcome this problem, we devise an underwater spot tracking software design approach based on Qt and MATLAB mixed programming. The approach adopts the Mean Shift iterative algorithm for underwater spot target recognition and localization. A mixed programming method of MATLAB and Qt is used to create the software interface, build a water tank experimental platform, and import the spot photographs. Spot target recognition and movement trajectory drawing are realized using the software, thus verifying the effectiveness of the algorithm. The final result is essentially consistent with the actual spot trajectory, and the maximum error offset is 7.28 pixel.

To meet the requirements of multichannel fluorescence correlation spectroscopy with a wide dynamic range, a digital correlator based on field programmable gate array (FPGA) technology was designed and implemented. The hardware structure was designed and implemented using a register-level hardware description language. Based on the characteristics of photon pulse counting signals, the multi sampling time correlation and time-division multiplexing methods were used to calculate the correlation function, which substantially improved computing efficiency and optimized hardware resource utilization. The time-division multiplexing of cross correlation was extended to triple correlation, and the corresponding method was extended to adapt triple correlation. Ultimately, a real-time computing triple correlator based on FPGA was realized. The calculation method of symmetric normalization ensured the accuracy of the correlation function. The designed photon correlator was implemented based on a single Xilinx Zynq-7100 FPGA chip, which performed various functions, including the real-time correlation of three channels auto-correlation, three channels cross-correlation, and one channel triple correlation, with the time resolution of 40 ns and dynamic range of 1.57 × 107.

Aiming at the problem of establishing the mathematical model of the electromagnetic-driven micro-electro-mechanical system (MEMS) micromirror applied to the laser radar, the discrete model of the electromagnetic-driven MEMS micromirror is established by combining the mechanism analysis method with the input-output method. A recursive least squares method with variable forgetting factor is proposed to identify the model parameters of electromagnetic-driven MEMS micromirror. By making the forgetting factor dynamic, the problem of "data saturation" is solved, so that as much input and output data as possible can play a role in parameter identification, and the accuracy of parameter identification is improved. Through the simulation and experimental verification of this method, the results show that the error of the model obtained by recursive least squares identification with variable forgetting factor is reduced by 9.2% compared with traditional recursive least squares identification.

The intensity envelopes and propagation characteristics of Lommel-Gaussian beams are investigated numerically based on gradient-index medium. The intensity expression of Lommel-Gaussian beams is provided. The zero-free region of Lommel-Gaussian beams decreases with decreasing spot of Gaussian beams, that is, the truncation effect of beams is more obvious. The spatial scale decreases with increasing half-cone angles and the hollow region of beam center increases with increasing topological charges. The spatial distribution and symmetry can be modulated by changing the asymmetric parameters. The intensity distribution of beams gradually changes from circular symmetry to axial-symmetry double-crescent pattern with increasing amplitude of asymmetric parameters and the symmetric axis of double-crescent pattern is rotated clockwise with increasing argument of asymmetric parameters. When the Lommel-Gaussian beams are propagating in a gradient-index medium, within a transmission cycle, the relative intensity distribution of beams has no change, only the beam scale has a periodic focus change. But in free space, the beam quickly evolves into two light spots. All results are helpful to study the application of Lommel-Gaussian beams.

Blind quantum computation refers to the delegation of complex computation from a client with limited quantum capabilities or complete classical abilities to a server possessing ample quantum power. This reduces computational demands from the client. To reduce the economic pressure of the client and improve the execution effectiveness of blind quantum computation protocols, this paper introduces two enhanced measurement-based universal blind quantum computation protocols utilizing single-particle measurements. These protocols cater to quantum inputs featuring either real or complex coefficients. Each protocol involves two participants: the client, responsible for quantum state measurements and the exchange of classical or quantum information, and the server, tasked with preparing quantum states without measurement requirements. These protocols stand in contrast to the existing blind quantum computation approaches wherein the client solely undertakes measurements. The proposed protocols considerably reduce both the client's quantum and delegated costs while maintaining correctness, universality, and the concept of blindness.

Kernel method has a wide range of applications in machine learning. The combination of quantum computing and kernel method can effectively solve the problem of increasing computational costs in classical kernel method when the feature space becomes larger. Researches show that the minimized quantum circuits based on kernel method can be reliably executed on noisy intermediate-scale quantum devices. Some classifiers based on the quantum kernel method that have been proposed so far still have certain defects in terms of fully mapping data and circuit architecture. Therefore, we propose a compact quantum classifier based on polynomial kernel functions. First, a polynomial kernel function is introduced to increase the classification iteration rate of nonlinear data, thereby improve the classification efficiency. On this basis, a compact amplitude encoding is further proposed to encode the data labels corresponding to the quantum state. Compared with the existing quantum kernel method classifier, the number of coding bits of the quantum circuit of the proposed model can be reduced from 5 qubits to 3 qubits, and the two-qubit measurement in the existing method is simplified to a single-qubit measurement in the proposed model. In addition, the model achieves the optimal variance of the quantum circuit parameters in the measurement stage, which can effectively save computing resource overhead. Experimental simulations show that the expected value in the proposed classifier model is closer to the theoretical one, and higher classification accuracy is obtained. At the same time, the model has a low degree of entanglement, which effectively reduces the overhead of the entire preparation work.

Atomic spin squeezing uses the interaction between light and neutral atomic ensembles to reduce the uncertainty of the atomic spin component, therefore reaching a sensitivity beyond the standard quantum limit in quantum precision measurement, which is expected to play an important role in the fields of time and frequency metrology, gravity precision measurement, fundamental physics tests, gravitational wave detection and dark matter exploration. This paper introduces the concept and criteria of atomic spin squeezing, and analyzes the methods for generating spin squeezed state through atom-light interaction in neutral atomic ensembles, and reviews the recent results and achievements and the application research progress of atomic spin squeezing in quantum precision measurement.

Compared to fully commercialized nitride blue light light emitting diode (LED), the external quantum efficiency (EQE) of current Aluminum gallium nitride (AlGaN) based deep ultraviolet LED is still at a relatively low level. This review first introduces the current development status of AlGaN based deep ultraviolet LED and analyzes the reasons for low EQE. Then, the research progress in improving the EQE direction of AlGaN based deep ultraviolet LED in recent years is elaborated from three aspects: carrier injection efficiency, carrier radiation recombination efficiency, and light extraction efficiency. Finally, the current challenges and future development opportunities of AlGaN based deep ultraviolet LED were discussed.

Fluorescence interference is a major challenge in Raman spectroscopy, as strong fluorescence will seriously affect the detection of Raman spectroscopy signals. This paper introduces several differential Raman spectrum restoration methods (integration method, curve fitting method, deconvolution method, etc.) of shifted excitation Raman difference spectroscopy for defluorescence technology, and discusses its principle, implementation, and performance characteristics. In addition, the application of differential Raman spectroscopy in food, medicine, agriculture and other fields is analyzed in detail, which shows that shifted excitation Raman difference spectroscopy has broad application prospects.

The research process of optical functional glass materials involves long research and development cycles and low efficiency. Greatly hindered the development of optical glass materials. The emergence of machine learning technology has greatly promoted the development of glass materials science. By learning the laws contained in the data, learning and predicting new data from the huge and complex glass data has accelerated the research and development process of optical functional glass. This paper summarizes and demonstrates several types of machine learning algorithms involved in the prediction of optical glass and briefly introduces them. On this basis, it focuses on summarizing the important applications of these theoretical algorithms in glass research, including accelerating and improving traditional glass research methods, assisting glass composition-property correlation prediction, and suggestions for optical glass formulation design. Finally, the application prospects and future development trends of machine learning in optical functional glass research are analyzed and forecasted.

Compared with traditional optical lenses, liquid lenses have the advantages of fast response, large zoom range, and high controllability, which are widely required in various fields, such as vision correction, microscopes, cellphone cameras, endoscopes, and bionic optics. This paper summarizes the technical developments in liquid lenses and briefly describes their working principle at home and abroad. Furthermore, it analyzes the related processing methods, performance indices, and application prospects of some typical liquid lenses. Finally, this work provides an outlook on the future development trend to provide useful references for further research on liquid lenses.

In the era of artificial intelligence and big data, the demand for data storage, transmission, and processing capabilities has surged. Thus, the prerequisites for data transmission, including bandwidth and communication speed, have experienced an escalation. However, owing to the influence of dielectric materials and transmission rate, the electrical interconnections in system-level packaging present strong phenomena, such as loss, reflection, delay, and crosstalk, which cannot meet the requirements of increasing bandwidth and communication speed. Consequently, advanced packaging technology and photoelectric co-packaging technology encapsulate optical modules and electrical chips within the same package, thereby reducing the interconnection length between them and parasitic effects. Furthermore, it has numerous advantages, such as wide band, anti-electromagnetic interference, low transmission loss and power consumption, and hence, it has become a research hotspot in recent years. This article discusses the basic concepts and advantages of optoelectronic co-packaging, introduces typical 2D, 2.5D, and 3D technologies and the latest developments at home and abroad, and analyzes the challenges that must be addressed as a new generation packaging technology.

The existence of three atypical environments involving irregular particles, nonisotropic particles, and nonuniform media is quite common. However, the transmission performance and operating distance of optical signals are badly affected due to particle scattering and absorption in the three atypical environments. For instance, low-visibility environments, such as fog, haze, and clouds, can reduce the safety of aircraft, cars, and ships, making it difficult to search and navigate in turbid waters. However, using polarization characteristics to characterize the transmission process in these atypical environments can provide feasible solution for extracting high-quality light signals and increasing operational distances. In this study, we explore the polarization transmission characteristics in three situations: irregular particles, nonisotropic particles, and nonuniform media. We analyze the domestic and international development of various nonspherical particles, present relevant data from the equivalent multilayer concentric particle model, and explain the effectiveness of addressing issues such as haze-scattering characteristics. Furthermore, we conduct a classification study on nonuniform media and analyze the impact of the medium on light transmission. By summarizing the development progress and current research status regarding scattering polarization characteristics of polarized light in the three atypical environments, we aim to clarify the importance of studying polarization transmission characteristics in such settings. Finally, we look forward to the development trend of polarization transmission problems in the three atypical environments.

Semiconductor saturable absorption mirror (SESAM) is the most commonly-used passive mode-locking device in ultrafast laser technology. Owing to its advantages of self-starting, low insertion loss, high integration, and flexible design, SESAM has a wide range of applications and excellent commercial prospects. This study introduces the mode-locking principle and current development status of SESAM and summarizes the current epitaxial structure, growth mode, and parameter performance of SESAM. It also provides a detailed description of its latest progress in mode-locking in solid-state, semiconductor, and fiber lasers. Moreover, the performance characteristics and future-development direction of various types of mode-locked lasers are presented.

InGaAs single-photon detectors are extensively used in laser 3D imaging, long-distance high-speed digital communication, free-space optical communication, and quantum communication. Different packaging formats, including coaxial packaging, butterfly packaging, and pin grid array packaging, have been designed for unit, line array, and small panel array devices. The impact of the temperature on the efficacy of InGaAs single-photon devices and the methodologies for controlling component temperature are discussed. Detailed comparisons and analyses of high-precision coupling methods for optical components such as microlenses, lenses, optical fibers, etc. to the semiconductor are provided. For high-frequency signal output, the lead type, wiring method, packaging structure design, and other issues are reviewed, and the development trend of the InGaAs single-photon detectors is forecasted.

Surface enhanced Raman scattering (SERS) is a non-contact, non-destructive and high-sensitivity spectral analysis technique. SERS has the capability to detect molecular fingerprint and has been widely applied to the subjects of materials science, chemistry, physics, geology and life science. Compared with the traditional rigid substrates, the flexible SERS substrates can conduct in situ and on-site real-time detection of analytes on non-planar surface. However, there are still some challenges in designing and fabricating the flexible SERS substrates with high-sensitivity and reproducibility. Therefore, we provide an overview of the recent advances in flexible SERS substrates. We discuss the fabrications, performances, applications and future prospects of five different types of the flexible SERS substrates, and provide some guidance for the research of SERS substrates.

Since the in-depth research on the theory and technology of luminescent materials, luminescent materials have been widely used in white LED lighting, optical imaging, optical storage, optical communication, optical fiber laser, and other fields. In recent years, it has been found that the luminescent materials prepared by introducing phosphorus as co-doped elements show unique advantages in optical properties, which has become the key factor to solve the bottleneck of luminescent properties of many luminescent materials. In this paper, the preparation methods and optical properties of phosphosilicate luminescent glass was reviewed. Several mainstream preparation methods of luminescent materials and their phosphorus doping technology were introduced, as well as the spectral characteristics of various luminescent ions in the coordination environment of P5+, which shows the great advantages of phosphosilicate luminescent glass and optical fiber in the fields of optical communication and optical fiber laser. Finally, the application prospect of a variety of phosphorus doped active special optical fibers is prospected.

Typically, graded-index multimode fibers feature certain spatiotemporal nonlinear effects such as geometric parametric instability (GPI), which gradually expands the spectrum of transmitted laser light under certain conditions and eventually evolves into a supercontinuum. This paper introduces the concept of GPI and its physical connotations; moreover, the status of research on GPI-induced visible supercontinuum generation in graded-index multimode fibers is reviewed, and an analysis on the influence of fiber and pulse parameters on the output spectrum is presented. In addition to this, realizing an all-fiber structure and using short wavelength lasers as pump sources constitute key future research directions. Overall, the GPI-induced generation of the visible supercontinuum is expected to break through the power limitation of the supercontinuum generated by small core traditional photonic crystal fibers.

Differential absorption lidar (DIAL) is an important equipment for the detection of noxious gases. It has a high demand for the wavelength and linewidth of the laser sources. In recent years, optical parametric oscillation and amplification (OPO/OPA) technology has made breakthroughs in medium and long-wave infrared laser, showing great potential in obtaining high-quality long-wave laser. The characteristics of different nonlinear crystals are collected. The performance of long-wave laser obtained by some crystal optical parametric oscillators is generalized, including output power, pulse energy, tuning range and output linewidth. Combined with the theoretical gain linewidth calculation and recent experimental research, the main problems in realizing narrow linewidth are analyzed and summarized, furthermore, the future technical route furthermore,the development direction are prospected.

As a common stem vegetable in daily life, potatoes not only contain rich carbohydrates but also contain minerals, lutein and other active substances beneficial to human health. Studies on the nutrients and solanine contained in the skin, flesh and sprout of potatoes are of great significance for food safety and potato quality assessment. First, the spectra of skin, flesh and sprout of potatoes are obtained by laser-induced breakdown spectroscopy (LIBS), and the nutrient elements and solanine in different parts of potatoes are analyzed. Second, the difference in spectral peak intensity between metallic and non-metallic elements in different parts of the potatoes is observed. Finally, the reason for the difference is discussed in terms of the local thermal equilibrium condition and the ratio of ion to atom densities by the calculation of the temperature and electron density of the laser-induced plasma. Results show that LIBS is a reliable and effective in situ and online test methods for the analysis of various elements in different potato parts.

To study the nitrogen fixation reaction path in micro-channel gas-liquid two-phase dielectric barrier discharge (DBD), we propose a method to determine DBD characteristics using emission spectra. Based on the experimental results obtained for gas-liquid two-phase DBD nitrogen fixation, the characteristic parameters and active particle composition of DBD plasma are derived using the measured emission spectra, facilitating an in-depth analysis of the DBD nitrogen fixation reaction path. The experimental results indicate that the proposed method can accurately determine the vibration temperature, rotation temperature, and active particle composition of N2 during the DBD nitrogen fixation reaction. This approach circumvents the plausible effects of traditional intrusive measurement methods on the nitrogen fixation reaction of DBD. Therefore, this study offers a novel, reliable, and practical method for investigating the gas-liquid two-phase DBD nitrogen fixation reaction path.

Metal elements in lubricating oil can directly reflect the wear status and position of the mechanical structure, and analyzing them quantitatively is an effective means of realizing fault warning and diagnosis. Based on laser-induced breakdown spectroscopy (LIBS) technology, the correlation coefficient method and threshold setting are used to narrow the range of feature wavelengths rapidly. The feature wavelengths are extracted accurately by the iterative predictive weighted partial least squares (IPW-PLS), uninformative variable elimination (UVE), and competitive adaptive reweighted sampling (CARS) methods. Finally, based on partial least squares (PLS) method, a quantitative analysis model of metal elements in lubricating oil is established to analyze metal elements in lubricating oil quantitatively. The experimental results show that the proposed CCPS method can improve the efficiency of characteristic wavelength selection and reduce the running time by more than 50%. The correlation coefficient RP2 and root-mean-square error prediction (RMSEP) values of CCPS-IPW-PLS are 0.9945 and 25.1678 μg/g, respectively. The RP2 and RMSEP values of CCPS-UVE are 0.9790 and 52.7363 μg/g, respectively, and the RP2 and RMSEP values of CCPS-CARS are 0.9939 and 25.0996 μg/g, respectively. These results prove the accuracy and efficiency of the proposed method. The approach provides a new way to perform the rapid, portable, and accurate detection of lubricating oil.

The harvesting period of spring tea significantly affects its economic value and consumer preference. To quickly identify different harvesting periods of spring tea, we employed laser-induced breakdown spectroscopy (LIBS) combined with machine learning algorithms. This approach was used to identify the before-brightness tea and before-rain tea of Mt. Lushan fog tea and Dog bull head tea. One hundred spectra were collected for each type of tea leaves and tea infusion, and the training and test sets were randomly divided in a ratio of 3∶2. The LIBS spectra were pre-processed with baseline correction and then 11 sets of spectral data were preferentially selected, and input into the linear discriminant analysis (LDA), support vector machines (SVM), K-nearest neighbor (KNN) and ensemble machine learning (EML) classification models for analysis, respectively. Findings showed that combining tea leaves and tea infusion data effectively identified the spring tea's harvesting period. This fusion approach exhibited superior stability and robustness. Specifically, the LDA model achieved recognition rates of 98.60% and 99.38% in the test sets for Mt. Lushan fog tea and Dog bull head tea, respectively. Therefore, this study demonstrates the feasibility of integrating LIBS with machine learning algorithms to discern different harvesting periods of spring tea.

At present, producing clean gas through anaerobic digestion is one of the main means to treat food waste. As food waste contains sulfur, H2S gas will inevitably be generated during anaerobic digestion. H2S gas is inevitably generated during anaerobic digestion due to the presence of sulfur in food wastes. The produced H2S can lead to corrosion in pipelines and environmental pollution. Thus, it is essential to measure its volume fraction online. Traditional H2S volume fraction measurement methods, such as methylene blue spectrophotometry, iodometry, and electrochemical methods, involve complex operation, slow measurement speed, and can easily be affected by other gases. In addition, these methods cannot be used to guide the timely adjustment of the working conditions of the desulfurization system. Therefore, we develope an approach combined the ultraviolet absorption spectroscopy and continuous wavelength integration method for the online measurement of H2S volume fraction. The linear relationship between the characteristic value of the absorption spectrum integration and H2S volume fraction is obtained by selecting a 210?230 nm band as the characteristic band, with a fitting degree >0.999. To measure the volume fraction of H2S, we prepare 200×10-6?1200×10-6 of H2S standard gas in a laboratory, and the maximum error of the measured value is 3.1%. Finally, the measurement device is applied to the anaerobic digestion of kitchen wastes, and the field test is conducted. The results demonstrate that the instrument can accurately monitor the change in H2S volume fraction of biogas during the anaerobic digestion process.

For the development and utilization of Rosaceae plant resources, it is of great significance to collect information on different Rosaceae plant species and clarify their family and generic relationships. In this study, leaves, petals, and stamens of different Rosaceae plant species are analyzed through Fourier transform infrared (FTIR) spectroscopy combined with principal component analysis (PCA), hierarchical cluster analysis (HCA), and soft independent modelling of class analogy (SIMCA). The results revealed that the leaves, petals, and stamens of Rosaceae contained polysaccharides, proteins, lipids, calcium oxalate, lignin, and other components, while the petals and stamens contained phenols in addition. The FTIR spectra of different types of leaves are found to be similar, but the absorption peak intensities in the range of 1660?1000 cm-1 differed significantly. Upon using this range for PCA, the first two principal components could achieve more than 97% of the cumulative variance contribution rate. Using HCA, 11 species of the plant could be correctly classified at the subfamily level. Combined with the SIMCA discriminant model, in the classification of Rosaceae plants with different leaves, petals, and stamens, the correct classification rate reaches 96.08% with the full spectral data in the range of 4000?400 cm-1, and 100% accuracy can be achieved with the data in the range of 1800?800 cm-1. The results reveal that FTIR spectroscopy combined with statistical analysis and discriminant modeling is a suitable method for accurately classifying different species of Rosaceae plants at subfamily and genus levels.

Shoe soles leave trace evidence that can easily be extracted at crime scenes. The Fourier transform infrared spectroscopy, combined with statistical analysis, is highly significant for testing and identifying physical evidence from the sole. In this study, five sole samples that are primarily made of cis-butadiene rubber are selected for identification. The original spectra of the soles that the main materials are the same are identical and difficult to effectively distinguish; therefore, the fingerprint region spectra in the approximate range of 1800?650 cm-1 are selected for the second-derivative analysis and two-dimensional correlation spectral analysis. The results show that the differences in the spectra of the second derivatives are not significant between samples, whereas the number, position, and response order of the cross peaks in the two-dimensional correlation spectra differ; this can be used to distinguish different sole samples. Therefore, using two-dimensional correlation infrared spectroscopy, shoe soles are useful for identifying physical evidence. Thus, two-dimensional correlation spectroscopy has great potential for application in the field of forensic science.

Colloidal quantum dot materials have pertinent applications in optoelectronic devices such as solar cells and photodetectors. Photocarrier radiometry technology is used to determine the exciton transport characteristics of a PbS colloidal quantum dot film containing trap states. A theoretical model ignoring net carrier transport between quantum dots is established, and the effects of exciton transport characteristics on photocarrier radiometry signals are subsequently simulated and analyzed. Finally, by conducting a frequency sweeping photocarrier radiometry experiment with different excitation powers, combined with the established exciton transport model, a variety of material parameters such as the effective exciton lifetime, carrier capture rate, and decapture lifetime are extracted. The experimental results confirm the validity of the proposed theoretical model.

The influence of pulse time delay (PTD) caused by the large-diameter lens on the spatiotemporal characteristics of a broadband laser focal spot is studied to design a high-energy laser system. To this end, diffraction transmission theory of broadband lasers in lenses, which is used in high-energy petawatt laser system with multi-pass amplified structure, is employed. It is found that when the aperture of the broadband laser reaches 360 mm×360 mm, the maximum PTD caused by the lens is approximately 2.5 ps. The spatiotemporal coupling effect peaks when the pulse width is 0.5 ps under the Fourier-transform-limit bandwidth of 3.2 nm and the beam quality is 1 diffraction-limited (DL). The time waveform is distorted, and the focal spot size corresponding to 90% energy concentration is doubled. However, when the compressed pulse width is more than 1 ps or the far-field beam quality is ≥5 DL, the spatiotemporal coupling effect weakens, and the influence of the PTD on focus can be neglected. The research results provide an important theoretical basis for the lens chromatic aberration compensation and fosus performance improvement of domestic high-energy petawatt laser systems.