Denoising has long posed a significant challenge for security cameras, even with the denoising algorithms, on which modern security cameras heavily rely. These algorithms often lead to a degradation of image edges, especially in low illuminance conditions. To tackle this problem, a low illuminance image denoising algorithm is proposed, which aims to minimize the loss of edge information while reducing noise based on pixel value deviations. In light of the human visual system, we construct an image pyramid from the pixel values, allowing us to analyze local and global pixel value differences and mitigate the noisy influence on pixels of medium value. Experimental results show that the proposed algorithm removes the noise signal in nighttime road images, preserves edge details, enhances the overall image quality compared to the classic wavelet denoising algorithm, and improves the signal-to-noise ratio according to the Imatest SNR test.

In order to improve the sensitivity of low refraction chemical monitoring, a surface plasmon resonance sensor based on photonic crystal fiber with gold film in open loop was designed in this paper. The effects of open-loop radius, pore size and thickness of metal film on the sensitivity of the sensor were studied systematically by using COMSOL Multiphysics 5.6. Finally, a low refractive index sensor with a refractive index detection range of 1.26-1.31 was designed in the working band of 2 800-4 700 nm. The average sensitivity of the sensor is as high as 22 500 nm/RIU, and the highest sensitivity is 33 000 nm/RIU. It has a good application prospect in the detection of low refractive index substances such as sevoflurane, haloether and fluorine-containing organic compounds.

As a major category of plant dyeing, tea dyeing has a deep cultural heritage while having good environmental protection performance. In order to accurately describe the spectral changes of tea staining, this work studied the relationship between the spectral reflectance of rice paper dyed with tea and the tea concentration. First, a spectrophotometer was used to measure the spectral reflectance of rice paper in the 400 to 700 nm band which was stained by tea leaves. Prediction models were constructed by the spectral reflectance of rice paper and tea concentration based on the partial least squares regression model, BP neural network and continuous projection algorithm(SPA) selected feature band, respectively. Then the spectral reflectance was used as an input variable to predict the tea concentration. The results show that the partial least squares method, BP neural network and continuous projection algorithm select characteristic bands to establish a model to predict tea concentration through the spectral reflectance of tea dyed rice paper, which has high robustness and reliability. SPA-BP neural network model has the best performance: the average prediction accuracy rate is 98.40%, the coefficient of determination is 0.9910, and the root mean square error is 0.843 3. This shows that it is feasible to predict tea concentration through spectral data of tea dyed rice paper.

Spectral processing holds immense significance in the research and application of optics. Various devices and instruments have been developed for specific tasks, including spectral filtering, shaping, analysis, and wavelength demultiplexing. However, advanced multitasking spectral processing equipment has been lacking. In this work, we have designed a diffraction neural network for spectral filtering, comprising a phase-modulated diffraction layer and a detection layer. During the training process, wavelength parameters were incorporated to achieve the processing of broadband signals. By designing a tailored loss function, we gained control over the output spectrum. Taking the broadband signal in the visible light band as an example, we achieved both single and dual passband spectral filtering, with adjustable central band widths and relative intensities. This research demonstrates that optical diffraction neural networks can effectively handle broadband spectra, laying the foundation for tackling more complex spectral processing tasks in the future.

ortex beam carries orbital angular momentum and exhibits a helical phase, with a Poynting vector oriented at an angle to the optical axis. The angular component of the vortex beam's Poynting vector causes a rotational Doppler effect, which allows direct measurement of rotational velocity. The linear and rotational Doppler effects of vortex light can be used to detect both linear and rotational velocities of an object, providing a comprehensive view of its compound motion. On this basis, the target is detected using the vortex light superimposed with different orbital angular momentum modes. These different orbital angular momentum modes cause different frequency shifts, which, when combined with the frequency shifts resulting from the linear Doppler effect, allow us to measure the specific velocity components of the compound motion. In this paper, we propose a measurement model for compound motion using superimposed vortex beams and analyze how different motion states affect the detection results.

The method of simulating cone lens with spatial light modulator is the most widely used method to generate perfect vortex beams at present. However, the ring width of the generated beam can not be controlled in real time by this method. Here, we propose an approach to generate and control the perfect vortex beams based on computer-generated phase holography in Fourier space. Through theoretical analysis and experimental measurements, We demonstrate that the method presented in this paper enables real-time control of topological charge, radius, and thickness of the generated ring beam by using a coded phase mask. The method offers simple optical path, high beam quality, and simple operation with only one of optical path ajustment. Furthermore, the proposed method can also be used to generate and control other abnormal perfect vortex beams, such as elliptic perfect vortex beams. The experimental results are in good agreement with the theoretical results. Thus, the proposed method based on phase-only computer-generated hologram presents a versatile and simple way of generating and controlling perfect vortex beams.

An electromagnetic wave absorber is a device that can absorb and annihilate electromagnetic waves, which is widely used in various fields of military, science and technology, and people’s livelihood. Absorbers based on metamaterials have received considerable attention due to their potent ability to absorb electromagnetic waves, ultra-thin characteristics, and design flexibility. In this paper, we design a broadband metamaterial absorber based on metal-dielectric-metal (MDM) structure, and analyze the absorption principle and physical mechanism, and simulate the parameters of the structure. The results show that the metamaterial absorber has an absorption rate higher than 80% for incident light from 490-1790 nm, with an average absorption rate of up to 90% and an optimal operating angle of 30°. In addition, the polarization-dependent tuning can be performed by modifying the symmetry of the cell structure. The proposed broadband metamaterial absorber is well suited for solar photovoltaic, optical communication, filtering and sensing applications.

In order to analyze the mechanism of chiral signal enhancement of spherical particles, the Mie scattering characteristics of spherical particles are studied based on the T-matrix method, and the mechanism of chiral signal enhancement is analyzed based on the regulation of incident beam with orbital angular momentum (OAM) and particle’s characteristic parameters. The wave front of tightly focused linearly polarized light is regulated, the dichroism of OAM is measured by regulating the sign of OAM carried by the beam, and the relationship between the order of OAM and the intensity of the chiral signal is studied. When the order of the OAM carried by the beam is matched with the size of the sphere, the scattering circular dichroism signal can be enhanced by 22.8 times compared to that of circularly polarized light. The influence of particle size and chiral parameters on OAM dichroism signal is also analyzed.

In order to meet the requirements of micro-electro-mechanical system (MEMS) two-dimensional laser scanning system for microscope objective with small entrance pupil diameter, large incident angle and large field of view, a near-infrared infinite conjugate microscope objective with an entrance pupil diameter of 1.1 mm and a large scanning angle of ± 18 ° is designed by using optical design software Zemax. The total length of the objective lens is less than 23 mm. The numerical aperture reaches 0.4 and the resolution is 1.26 μm. The working distance is 900 μm. The aberration correction is good.The designed microscope objective can meet the needs of use. The results show that the microscope objective can meet the requirements of MEMS two-dimensional galvanometer laser scanning system for portable skin detection instruments.

Nitrogen ions emit narrowband coherent emission under the pump of intense femtosecond laser pulses of different wavelengths (mid-infrared, near-infrared, or ultraviolet). The 428 and 423 nm radiation of the nitrogen ions obtained by excitation with 400 nm femtosecond laser pulses has received less attention and their properties are unknown. In this study, the polarization of the 428 nm emission and its dependence on the nitrogen gas pressure and the pump laser energy are systematically measured. It is found that the polarization of the 428 nm emission is the same as the linearly polarized pump pulses. Moreover, the radiation signal presents nonlinear dependence on the gas pressure and the pump pulse energy. Based on the modeling of the strong-field ionization and the coupling of different energy levels of nitrogen ions in presence of the laser field, the population distribution of the nitrogen ions is simulated numerically. It is revealed that population inversion between the relevant energy levels of the upper level state $ {\mathrm{B}}^{2}{\mathrm{\Sigma }}_{\mathrm{u}}^{+} $and the lower $ {\mathrm{X}}^{2}{\mathrm{\Sigma }}_{\mathrm{g}}^{+} $level can be robustly established for a relatively large range of pump laser intensity, which agrees with the experimental observation.

With a certain intensity, a femtosecond laser focusing in the air will generate an air plasma and induce a shock wave. In order to study the propagation process of the shock wave, an ultrafast time-resolved vortex filtering imaging technique is introduced in this paper, and the observed dynamic process of the shock wave is analyzed. The shock wave from air plasma was observed when pumped by a 1.5 mJ femtosecond laser focused into the air through a lens, and the dynamic evolution of the shock wave in the period from 3-15 microseconds was analyzed. The results show that the femtosecond laser plasma air shock wave diffuses outwards in an asymmetrical spherical shape, and the propagation velocity is different along the laser propagation direction and behind the laser propagation direction, which are 372 m/s and 341 m/s, respectively. This observation is different from the traditional point explosion model, namely the symmetric case. We give a reasonable explanation for this asymmetric dynamic process.

In order to further study the shape detection of optical frequency domain reflectometry(OFDR), and effectively calculate the shape and position of optical fiber in application scenarios such as deformation monitoring, this paper designed an algorithm to reconstruct three-dimensional shape using the optical fiber strain data measured by distributed optical frequency domain reflection technology. Compared with the existing algorithm, spline interpolation was added to the data processing, which improved the precision of shape reduction, and the simulation experiments were used to verify the algorithm. Firstly, a calculation method was designed to obtain the sampling values of curvature and bending direction of three-core optical fiber from the strain data, and the curve equation was constructed by combining the Frenet-Serret formula. Then the finite element analysis software was used to model and extract the S-shape strain data and the S-shape fiber was reconstructed in the three-dimensional space. The results show that the position error increases with the increase of fiber length. The root mean square error is 0.996 mm, and the maximum error per unit length is 0.0824%. The results show that the algorithm can recover the original curve well.

The vibration sensing technology based on optical frequency domain reflectometry (OFDR) has attracted a lot of research due to its superior electromagnetic interference resistance, good corrosion resistance, convenient installation and accurate positioning capability. Phase demodulation algorithm is the key technology of vibration sensing based on OFDR. There are many phase demodulation algorithms applied to OFDR vibration sensing, but they are more or less affected by modulation depth or light intensity. In order to reduce the impact of these two factors on the demodulation results at the same time, this paper proposes an improved phase generation carrier algorithm, which eliminates the nonlinear terms of the light intensity term and modulation depth term in the demodulation signal through mathematical calculation. Compared with the traditional algorithm from both theoretical and simulation aspects, the performance of the improved algorithm is verified, which can reduce the impact of these two factors on the demodulation results at the same time. The work of this paper can be used to improve the stability of the vibration sensing system.

Image semantic segmentation requires fine detail information and rich semantic information, but in the stage of feature extraction, continuous down-sampling operation will lead to the loss of spatial details of objects in the image. To solve this problem, a semantic segmentation algorithm based on double-branch structure is proposed, which can obtain rich semantic information effectively and reduce the loss of object details in feature extraction stage. One branch of the algorithm uses shallow network to retain high-resolution detail information which is helpful for object edge segmentation, and the other branch uses deep network for downsampling to obtain semantic information which is helpful for object category recognition, and then the effective fusion of the two kinds of information can generate accurate pixel prediction. Experimental results on Cityscapes and CamVid datasets show that the proposed algorithm achieves better segmentation performance under fewer parameters than existing semantic segmentation algorithms.

This paper mainly solves the problem of accurate positioning of reference points in deflection measurement of concrete structures. The fitting algorithm of Gaussian spot is derived. The existence of the parameter Krame-Rowe lower bound is proved, and the corresponding parameters are optimized by the Levenberg-Marquardt method. The experimental results show that the root mean square error attenuated by the center extracted by the Gaussian fitting spot localization algorithm based on nonlinear parameter optimization is 0 when the signal-to-noise ratio is 40 dB. As the contrast decreases, the extraction accuracy of the three methods deteriorates. The Gaussian fitted spot localization algorithm based on nonlinear parameter optimization is superior to other algorithms before the contrast drops to 25% of the original image, but this advantage disappears when the contrast continues to decrease. It shows that in the case of good contrast, it can not only ensure accuracy but also improve robustness.

Optical information processing technology has the characteristics of high speed and parallelism. The wavelength of light is short and the information capacity is large. At the same time, it has many attributes such as amplitude, phase, wavelength and polarization, which could be the carrier of multi-dimensional information. Therefore, optical encryption is of great significance in the field of information security transmission and is widely used in the field of image encryption. For multiple image encryption, this paper proposes a multi image encryption algorithm based on cascaded phase iteration and computational ghost imaging. This method can encrypt multiple images efficiently at the same time, which is simple, safe and reliable, and has less transmission data. The encryption effect of this method is evaluated by using correlation coefficient, and the effectiveness and security of this method are verified by simulation.

Microscopic techniques cannot resolve subwavelength scale structures due to the diffraction limit of optical imaging systems. Super-resolution imaging of single nanoparticles has been achieved by saturation scattering suppression imaging techniques, but when it comes to ensembles of nanoparticles, the coupling between nanoparticles needs to be considered. Far-field super-resolution optical imaging can be achieved on ordered gold nanorod arrays using a two-beam method beyond the diffraction limit. In this paper, a 5×5 gold nanorod array with an aspect ratio of 2 is designed, the thermal distribution of the gold nanorod array under continuous-wave laser is calculated by the vector light field theory and thermal diffusion theory, and the scattering imaging under dual-beam laser, i.e., pulsed excitation light and continuous-wave suppression light, is simulated. The simulation results show that the continuous-wave laser can effectively suppress the pulsed laser scattering of gold nanorod arrays, and the two-beam approach achieves super-resolution imaging with 80 nm resolution.

The main method for melanoma is photodynamic therapy (PDT), and the design of more efficient photosensitizers is the key point to melanoma therapy. To promote the therapeutic effect of PDT, a novel photosensitizer was designed. The substrate was the Protoporphyrin IX (PpIX), then the demethylated drug SGI-1027 and PpIX were encapsulated by the synthesized PMHC18-mPEG to form the SGI@PpIX-mPEG complex system. PpIX exposed to illumination causes cells to produce a large amount of reactive oxygen species (ROS), which would increase the content of the downstream protein Caspase-3. The demethylated drug increases the content of GSDME. Research indicates that the synthesized novel photosensitizer drug can not only generate reactive oxygen species to kill cancer cells, but also further lead to pyroptosis and enhance the effect of photodynamic therapy through the interaction between Caspase-3 and GSDME.

A long-term stability control scheme of the dynamic cavity length based on coupled optoelectronic oscillator is proposed. When the cavity length of the optical resonator changes, the resonant phase variation of two selected positions in the optical resonator is measured by the IQ mixer, and the optical delay line in the regeneration cavity is feedback-controlled to following compensation of the regeneration cavity length, and the controlled mode-locked output of the coupled optoelectronic oscillator with variable cavity length is realized, to convert the changing cavity length into the changing resonator frequency for measurement. After systematic experiments, the optoelectronic oscillator can output a variable locked microwave signal, and keep the side mode suppression ratio better than 47.26 dB, the power jitter less than 0.28 dB, and the lock phase error jitter within ±1.5° within 1 hour.

To address the challenges of complex process and poor substrate adaptability in current low-dimensional material transfer schemes, a fixed-site transfer method based on flexible polymer film polydimethylsiloxane (PDMS) is proposed in this paper. The deformation of PDMS flexible film is the basis for its close adhesion to different substrates. For different target substrates, only the corresponding substrate micro-adjustment system cover plate need to be replaced, and in combination with the three-dimensional displacement mechanical system, the universal fixed-point transfer of one-dimensional and two-dimensional materials is realized. This method avoid the strict conditions of vacuum adsorption and substrate heating during the transfer process, which effectively reduce the difficulty of the fixed-point transfer of low-dimensional materials and improve the transfer stability and versatility. In addition, this method also enable the construction of homogeneous junctions or other vertical structures of low-dimensional materials, thus greatly improving the structural richness of low-dimensional materials.

In order to further explore the new detection technology of terahertz based on cesium Rydberg atom, we studied the radiation lifetime after atomic transition and the sensitivity of system noise limitation under different transition modes (S1/2→P3/2、D5/2→P1/2、D5/2→P3/2) using simulation under four-level Rydberg atomic model. The simulation results show that the atomic radiation lifetime after transition increases with the increase of its energy level principal quantum number. Among the three transition modes of the model, the atomic radiation lifetime of S1/2→P3/2 is shorter than the other two transition modes. For the shot noise limited sensitivity, the sensitivity value of D5/2 →P1/2 transition mode is the smallest, that is, the detection sensitivity of the system will be the highest in this transition mode. This conclusion provides a reference for the Redburg atomic terahertz detection technology and lays a foundation for weak signal detection in the field of biology and materials.

Increasing the energy of terahertz pulses has been one of the research hotspots of ultrafast optics in recent years. In this paper, based on the numerical model of terahertz wave generated by two-color laser plasma filament in air, in the range of tunneling ionization, we analyze in detail the optimal parameter combination of terahertz wave generated by two-color laser field and the physical mechanism of its change, so as to obtain the strongest terahertz wave radiation energy. We analyze its physical mechanism. The electric field of the combination of two-color laser fields is asymmetric, and the rapid oscillation enhances the acceleration process of electrons, resulting in larger electron number density and stronger cumulative net current along the plasma filament. When the electron density and net current increase, the single point terahertz radiation is stronger, and the terahertz waves radiated at each point of plasma filament are coherently superimposed, so a stronger terahertz wave energy is obtained in the far field. These research results provide a detailed parameter analysis and theoretical basis for enhancing the radiation energy of THz wave under different laser generation conditions, and focus on the influence of unusual wavelength combination and different relative phases on the generation of terahertz wave by laser wire drawing, which is of great significance for greatly enhancing the radiation efficiency of THz in the future.

The ultrafast carrier and phonon dynamics of SnSe2 thin films grown by chemical vapor deposition are investigated based on a self-built ultrafast pump-probe experimental system. By measuring the carrier relaxation process of the SnSe2 thin films with the variation of pumping energy density, the results showed that the thin films had an ultrafast carrier thermalization process and a composite process on the picosecond to nanosecond time scale. Accompanied by the ultrafast excitation and energy relaxation of photogenerated carriers, the SnSe2 thin films underwent lattice thermalization and generated coherent acoustic phonons of specific frequencies. The properties of the coherent acoustic phonons generated by the SnSe2 thin films were revealed by analyzing the variation of the acoustic phonon oscillation signal with the pumping energy density. The results of this study provide reference value for the study of the application of SnSe2 thin films in the field of optoelectronic devices.

Spatiotemporal optical vortices (STOVs) carrying transverse orbital angular momentum are a new type of optical pulse wave packet, and attract more and more attention from researchers around the world. In this paper, we present a method of generating linearly polarized STOVs with controllable polarization states on the focal plane of a high numerical aperture lens. The incident wave packet is pre-split to overcome the spatiotemporal astigmatism caused by the focusing lens to the STOV. The three dimensional spatiotemporal distributions of the highly confined STOVs with different polarization states are simulated based on Richards Wolf vectorial diffraction theory to analyze their intensity and phase characteristics. The obtained horizontally polarized, vertically polarized and 45° polarized highly confined STOVs manifest the feasibility of the presented method.

The focus of this paper is the sub-wavelength imaging of gradient index photonic crymstals. The gradient index photonic crystals is a parallel plate composed of silicon and circular air holes. The gradient change of photon crystal refractive index is realized by adjusting the structure of each column of pores. The focusing process of the gradient index photonic crystals is simulated by finite-different time-domain (FDTD) algorithm. The results showed that proper modification of the optical path difference could greatly optimize the focusing effect. Furthermore, changing the focal length of photonic crystals and the structure of the central air hole could also optimize the focusing effect. By combining the above three elements, the gradient index photonic crystal was finally designed which could realize sub-wavelength focusing. The half-width of the focused spot was 0.3447 λ , which was located at 1.45 λ outside the photonic crystal. To improve application performance, a dynamic focal length adjustment system was designed on the gradient index photonic crystals. The focal length range of 1.1374 λ～2.6264 λ could be adjusted without changing the structure of gradient index photonic crystals. Meanwhile, the half-width of the focal spot was less than 0.4 λ.

The ideal perfect vortex beam is a special beam whose intensity distribution does not change with the change of the topological charge. Compared with ordinary vortex beam, it can greatly improve the application efficiency in particle manipulation and optical fiber transmission. In order to explore the free space propagation characteristics of the perfect vortex beam, this article uses Hank transformation to calculate and analyze the effects of the topological charge, the initial surface ring radius and the ring width on its diffraction characteristics in detail, it is found that the perfect vortex beam does not have the characteristic of non-diffraction, and the halo will broaden with the increase of the diffraction distance and gradually transform to the Bessel function. When the radius of the initial surface increases or the width of the ring decreases, the diffraction effect increases, and the effect of the ring width is greater than the ring radius. Compared with the previous two cases, the topological charge has less influence on the diffraction effect. The research in this paper is expected to provide a useful theoretical reference for the further application of the perfect vortex beam.

In this paper, terahertz photoinduced force microscopy (THz PiFM) is designed and built, which realizes the near-field photoinduced force nanoscopic imaging measurement in the terahertz band for the first time. Based on the atomic force microscopy, the system uses the sensitive detection ability of the probe to the force, and realizes the terahertz near-field microscopic imaging without detector. The system detected the light field gradient force generated by the near-field dipole interaction between the probe and the sample. The near-field nanoscopic imaging characterization of monolayer MoS2 grains excited by visible light was carried out, and the mechanism of near-field optical signal enhancement at the grain edge was analyzed. The results show that THz PiFM has a highly sensitive detection capability for carriers in two-dimensional materials. Compared with the traditional terahertz near-field microscopy imaging technology, THz PiFM does not require terahertz detector, and is a new low-cost, high-performance terahertz near-field microscopy imaging technology, and can achieve superior spatial resolution and imaging signal-to-noise ratio.

Electronic endoscope is an important equipment in the modern medical instruments. With the increase of production, automatic welding of endoscope signal line has become an inevitable trend. A field programmable gate array (FPGA) image processing system for welding spot detection of endoscope lens module was designed to accurately and efficiently capture the welding spot coordinates of endoscope lens module. In the whole system, OV5640 is used as the image acquisition device to collect the image data of the target board. Image processing is carried out by Verilog HDL hardware description language for welding spot detection and defect discrimination algorithm. The hardware test results show that the system can collect the coordinates of solder joints in real time and detect the defects between solder joints. The maximum error of the collected coordinates is less than 0.1mm. the detection accuracy is high, and the real-time performance is high. The system has a wide application prospect.

In order to make the orbital angular momentum (OAM) mode generated in the optical fiber more integrated, a method to generate the orbital angular momentum mode using photonic crystal fiber (PCF) is proposed. By designing a special PCF, the transmission speeds of the eigenmodes of the odd and even modes are different, and thus a π/2 phase difference is formed after transmission for a certain distance to produce an OAM mode. The PCF is composed of a central air hole, a silica ring layer and an outer cladding layer. The outer cladding layer is composed of two layers of circular air holes. The number of circles in each layer is 2n+2, corresponding to the n-order OAM mode. The finite element method was used to carry out three-dimensional numerical simulation analysis of the designed optical fiber, and the +2, +3, +4, and +5 orders of OAM modes were successfully generated. The PCF method for generating OAM modes meets the trend of future integration and miniaturization for optical fiber communication systems, and has potential application prospects in all-fiber mode division multiplexing systems.

Quantifying the geometric structure of packing particles is of great value for understanding the macroscopic mechanical properties of particle systems. In this paper, Cell was utilized to measure the geometric structure of disk particles in a two-dimensional silo. The probability distribution of Cell shapes satisfied the exponential function distribution and was independent of the system size. Furthermore, it was observed that under the condition of vibration driving, the triangular-shaped Cell had a surge, and the formation probability increased by 19%, while the probability distribution of the rest shapes of Cell still satisfied the exponential function distribution. The experimental results reveal the structural characteristics of ordered packing in disordered particle system at intermediate scale, and provide references for perfecting the theory of particle mechanics.

The emission characteristics of fluorescent molecules near the surface of noble metals have changed significantly due to the influence of surface plasmon resonance (SPR). They are widely used in the design of nano-devices such as fluorescent probes. The energy transfer mechanism between fluorescent molecules and metals is the basis for the design of such fluorescent probes. Therefore, in this paper, surface energy transfer (SET) and metal regulated spontaneous emission effect of single fluorescent molecules in the Au/SiO2/Ag core-shell nanostructure were theoretically simulated by using finite difference time domain (FDTD) method. The SET between fluorescent molecules and the hybrid plasmonic mode was studied. The results showed that due to the local surface plasmon resonance coupling between gold core and silver shell, the energy transfer efficiency between fluorescent molecules and metals shows a d10 relationship, which d is the distance from the fluorescent molecules to gold surface. That result is obviously different from the conventional FRET effect and the SET effect of single metal structure. It is expected to be applied in the development of nano light sources and biosensors.

Coherent Anti-Stokes Raman Scattering (CARS) is a stimulated Raman process, which has the non-resonant background (NRB), leading to peak shift and spectral distortion in the spectrum. In this letter, we use a femtosecond laser as the light source and a grating filter system generating narrow-band pump light. The femtosecond laser excites photonic crystal fiber, producing a supercontinuum spectrum as Stokes light. Two beams excite the samples simultaneously after modulated to circular polarized lights to produce CARS spectrums. We illustrate that circularly polarized light can effectively remove the non-resonant background in the CARS spectrum of anisotropic materials by simulation. Thus, the CARS spectrum has a similar spectral line shape to that of spontaneous Raman. The experimental results of CARS spectrums of polystyrene and liquid crystal samples generally agree with the calculations, proving that circularly polarized CARS spectroscopy is an effective method to remove the NRB of CARS spectrum.

Semi-floating gate field-effect devices based on graphene have been extensively studied due to their nonvolatile memory characteristics. In this paper, a graphene field-effect device with few-layer graphene as the channel, hexagonal boron nitride as the tunnel barrier layer, and graphene as the charge trapping layer is fabricated. Because of its unique semi-floating gate structure, the transfer characteristic curve has double Dirac points, which are systematically studied. At the same time, we get the stable retention characteristics of the device. Within 200 s, the device program and erase current ratio can be maintained at about 20 μA. Our research is helpful realizing two-dimensional optoelectronic devices based on the semi-floating structure.

Aiming at the problem of redundancy caused by the large amount of training sample data in the study of spectral reflectance, a sample classification method based on RGB information is proposed in this paper. Firstly, the color is clustered and the number of clusters is determined. Then, the BP neural network is used to reconstruct each spectral reflectance. The experimental results are evaluated by color difference, root mean square error and fitness coefficient, and compared with principal component analysis algorithm. From the experimental analysis, it can be concluded that the spectral reflectance reconstruction effect is the best when the number of clusters is 7. The average CIE2000 chromatic aberration is 0.836. The average root mean square error is 0.0149, and the average fitness coefficient is 99.82%. Finally, the color blocks with large reconstruction chromatic aberration are optimized. Experiments show that color clustering method can be well applied to spectral reflectance reconstruction.

Light source is the core component of projector display system. Laser light source has the characteristics of high brightness and long life, but it has the problems of high cost and speckle phenomenon. Combining laser with excited fluorescence as projector light source can effectively solve the problems. In this paper, the YAG phosphor and laser unit are combined into a hybrid light source. The influence of phosphor concentration and operation temperature on the luminous characteristics of the hybrid light source was investigated. The experimental results show that the brightness and chromaticity of the hybrid light source increase with the increase of the phosphor concentration, and the conversion efficiency of phosphor decreases with the increase of working temperature. The research results verify the feasibility of the laser-fluorescence hybrid light source for the projector, which not only reduces the manufacturing cost of the whole machine and solves the speckle problem of the laser light source, but also reduces the precision requirements of the optical components and improves the success rate of mass production.

The optical properties of metallic materials change with the thickness of the film thickness, resulting in the change of their spectral characteristics. If the film is deposited by thermal evaporation or sputtering, the neutrality of Ni80Cr20 film is poor when the thickness is too thin or thick. The theoretical calculation results show that increasing the proportion of chromium in Ni-Cr alloy can improve the neutrality of the thin film, while the proportion of nickel needs to be increased for the thick film. As for the opposite spectral characteristics of the thin and thick films, intentional fractionation and increasing the proportion of Ni are proposed to improve the spectral neutrality, respectively. The test result shows that the improved coating process is effective.

In this paper, the terahertz near-field response of monolayer MoS2 and WS2 grains prepared by chemical vapor deposition was investigated by terahertz scattering scanning near-field optical microscopy (THz s-SNOM). No resolvable terahertz near-field response was detected in the absence of visible excitation, indicating that the grains have a low doped carrier concentration. With visible light excitation, we were able to measure a terahertz near-field micrograph that exactly matches the grain profile due to the terahertz near-field response of the photogenerated carriers. Under the same photoexcitation conditions, the terahertz near-field response of MoS2 is stronger than that of WS2, it reflects the difference of carrier concentration or mobility between them. The results show that THz s-SNOM combines ultra-high spatial resolution and sensitive detection of photogenerated carriers. It is uniquely suited for micromechanics studies of the optoelectronic properties of two-dimensional semiconductor materials and devices.

Spin-exchange relaxation free（SERF）atomic magnetometer is a kind of ultra-sensitive magnetometer, and its miniaturization is very important for the application of magnetometer. The layout of optical path is the key factor that restricts its size and sensitivity. In this paper, a single beam miniaturized atomic magnetometer is designed. The magnetometer is a cylinder with a diameter of 21.2 mm and a height of 40.5 mm. Thermal simulation experiments are carried out on the magnetometer. The experimental results show that the design is reasonable in structure and easy for multi-channel measurement, and has practical application value in the field of biological magnetic field measurement such as magnetoencephalography and magnetocardiogram.

Based on the silicon dielectric cylindrical photonic crystal, the finite-difference time-domain (FDTD) method is used to investigate the inverse Goos-Hanchen (GH) shift of Gaussian beam at the photonic crystal interface. By adding a silicon lens on the lower surface of the photonic crystal, the influence of the incident angle of Gaussian beam, the curvature radius of the silicon lens and the temperature on the inverse GH shift of the photonic crystal is studied.The results show that the maximum inverse GH shift angle is larger than the geometric ideal total reflection angle. The addition of a silicon lens with the focus in the center of the photonic crystal surface can significantly enhance the inverse GH shift. When the curvature radius of the silicon lens is 170, the inverse GH shift increases by 1.7 times as much as that without the lens. The influence of temperature on the inverse GH shift of photonic crystal at different incident angles is studied. It is found that when the incident angle of Gaussian beam is 26 degrees, the inverse GH shift has a wide range of variation with temperature, and the linearity of variation curve is better, which is convenient for temperature monitoring.

In order to investigate the coupling effect of the two-layer array and the resulting upper and lower ring dipole modes, a microwave method was used to introduce a split resonant ring array structure in which the intermediate separator and the upper and lower surface were placed. Firstly, the upper ring dipole mode of the structure is excited by microwave, and then the dielectric plate is coupled to the lower ring dipole to realize the ring dipole cascade coupling, by adjusting the resonant ring up and down the number of array, the size of the resonant mouth, as well as the change of the medium plate in the middle of the dielectric coefficient. The excitation and coupling effects of ring dipoles in artificial localized surface plasmas by microwave frequencies can be studied. The results show that this mode can produce multi-peak ring dipole effect, which enriches the understanding of the coupling effect between artificial local surface plasmon ring dipole modes, and lays a foundation for the design and application of new sensors.

In this paper, the ultrafast optical response of chemical vapor deposition(CVD) grown ReS2 thin films is investigated by means of ultrafast time-resolved spectroscopy. The optical pump probe study shows that the ReS2 thin films have ultrafast carrier thermalization processes and sub-nanosecond scale compounding processes. Optical pumping terahertz emission tests show that the ReS2 films are capable of producing terahertz radiation with a spectral width of 2.5 THz under femtosecond laser pumping. The polarity of the terahertz radiation is reversed with the change of the pump light incidence angle. The analysis shows that the main physical mechanism of terahertz emission from femtosecond-pumped ReS2 films is the surface field effect. The microscopic mechanism elucidated in this study has important reference value for the application of ReS2 thin films in ultrafast and terahertz optoelectronic devices.

Integrated terahertz filter is one of the basic components of integrated terahertz communication system. In order to make the terahertz filter adjustable on chip, a terahertz tunable filter based on temperature control system is proposed. Compared with other terahertz filters, the proposed tunable on chip filter has the advantages of simple tuning method and small size, and can be well integrated with other terahertz devices on the chip. The temperature of the wafer is changed by the temperature control system, and the refractive index is changed by the thermo-optical effect of the silicon material, so that the coupling state of the microloop is changed, and the resonant peak of the THZ filter is shifted. In the process of heating the heating plate from 30 ℃ to 90 ℃, the center frequency of the resonant peak near 180 GHz of the terahertz tunable filter decreases gradually from 180.453 GHz to 180.224 GHz with a range of 0.229 GHz, the resonant depth changes gradually from -68 dB to -44 dB, and the half-height width changes gradually from the original 0.04 GHz to 0.246 GHz.

In order to study transient terahertz radiation from layered ZrTe5 (zirconium pentatelluride) excited by femtosecond pulses, terahertz time domain system was used to test and analyze the terahertz emission. By analyzing the relationship between terahertz electric field of layered ZrTe5 and intensity/polarization of femtosecond laser pulse, it was obtained that the main mechanism of terahertz radiation generation by layered ZrTe5. At the same time, the terahertz radiation intensity of layered ZrTe5 and intrinsic GaAs (gallium arsenide) under the same pumping conditions was also compared. Studies have shown that the layered ZrTe5 has narrow band gap structure, shallow absorption depth, larger residual energy of photogenerated electrons and higher carrier mobility, which has better performance than traditional semiconductors in terms of terahertz generation. The experimental research provides a reference for the discovery of efficient and highly integrated terahertz radiation sources.

Infrared gas sensor is often used in the detection of sulfur hexafluoride gas. By measuring the infrared absorption spectra of air and sulfur hexafluoride gas, we understand the spectral requirements of the filter based on non-dispersive infra-red (NDIR) gas sensor. Then, monocrystalline silicon is selected as substrate, and germanium and zinc sulfide are selected as high and low refractive index materials separately. Two kinds of film structures, narrow-band pass film structure and cut-off film structure, were designed. The infrared filter with central wavelength of 10.562 μm, bandwidth of 175 nm, peak transmittance of 80.2% and cut-off range of 2～18 μm (except the pass band) , was prepared by selecting reasonable process parameters. Finally, the filter met the engineering application by environmental test and sensor test.ental test and sensor test.

In order to study the influence of particle shape on the avalanche movement process of particles in the drum, we use the speckle visibility spectroscopy and image method to measure the intermittent avalanche movement of spherical particles and irregular particles with a diameter of 0.5 mm. The research results show that the avalanche process of spherical particles is different from that of irregular particles. Irregular particles will have two compaction phenomena, single compaction and double compaction, and the probability of occurrence of double compaction phenomenon is different under different filling degrees. The duration of single and double compaction also has a different proportional relationship with the filling degree. Additionally, it is found that the tilt angle of irregular particles is larger than that of spherical particles, and the larger the gravitational potential energy of the particle accumulation before compaction of irregular particles, the easier it is to produce double compaction.

Lead cesium perovskite nanocrystals have become ideal triplet sensitizers in photovoltaic and luminescent applications due to their high fluorescence quantum yield and quantum confinement effect. In this paper, three-monolayer CsPbBr3 nanoplatelets (NPLs) were used as triplet donors to achieve efficient triplet energy transfer (TET) from NPLs to 1-naphthalene carboxylic acid (NCA). CsPbBr3 NPLs were synthesized by ligand-assisted reprecipitation at room temperature. After binding with NCA, the steady-state fluorescence of NPLs was quenched substantially, the fluorescence lifetime was shortened from 6.743 ns to 0.995 ns, and the TET efficiency was as high as 85.3%. Compared with the large nanocubes, the quantum confinement is the key to obtain high-efficiency TET for CsPbBr3-polycyclic aromatic hydrocarbons (CsPbBr3-PAHs) complex system. The results indicate that CsPbBr3 NPLs can be used as triplet sensitizers in the fields of photon upconversion, photocatalytic oxidation-reduction reaction and room temperature phosphorescence based on TET.

In order to solve the problem of long-time operation of a fiber-based frequency comb, the control method of locking the repetition rate (fr) and carrier envelope phase offset frequency (f0) of optical frequency comb is improved. Two thermo-electric coolers (TEC), an upper one and an lower one, are used to control the temperature of frequency comb. By adjusting the TEC temperature, the stability of fr and f0 can be confined in the range of 10 and 600 Hz, respectively. Then, fr and f0 were further stabilized by the feed-back control of the optical path and the pump power, respectively. Finally, in 170-hour operation, the standard deviations of fr and f0 were measured as 0.83 and 280 mHz, respectively. The results show that the method can realize the long-term operation of the optical frequency comb and enhance its adaptability to the environment.

Aflatoxin B1 (AFB1) is a fungal toxin common in crops and it is the most toxic of all mycotoxins which can cause cancer. Thus, quick and effective detection of AFB1 is important for food security. Here, a simple and sensitive optical sensor based on surface-enhanced fluorescence (SEF) technique was designed to detect AFB1. We used nanoporous gold (NPG) as the substrate. The AFB1 aptamer (Cy5-DNA1) and AFB1 complementary aptamer (SH-DNA2) were successively assembled on the surface of NPG to form the optical sensor for AFB1. Competitive binding between AFB1 and Cy5-DNA1 released Cy5-DNA1 from NPG, leading fluorescence intensity of Cy5 to fall. AFB1 was detected by monitoring the variation of the fluorescnece intensity of Cy5 and the final detection limit was 10-7μg/L with a linear dynamic range 4 orders of magnitude.

The super lens with refractive index of -1 can achieve perfect imaging theoretically, but the photonic crystal with equivalent refractive index of -1 does not meet the conditions of permittivity ε=-1 and permeabilityμ=-1. The impedance of the photonic crystal does not match the free space, and the incident light at some angles cannot be coupled with the Bloch wave in the photonic crystal, resulting in the loss of these light information. It limits the imaging resolution. In order to improve the imaging resolution, a subwavelength grating is set on the surfaces of the photonic crystal and the coupling efficiency of the incident light to photonic crystal is improved. By adjusting the grating period, high spatial frequency components are involved in the imaging and the transmission of low frequency components is suppressed. With the subwavelength grating set on the surfaces, the imaging resolution of photonic crystal increases from 597 lp/mm to 850 lp/mm, which breaks through the diffraction limit.

In order to display the luxmeter of illumination and the induced voltage of illuminance, we design illuminometer based on a single chip microcomputer simulation, and the photoelectric conversion circuit, amplifier filtering circuit, A/D conversion circuit, display circuit and alarm circuit. The hardware circuit system is built. The debugging is completed. Experiments show that the system of illuminometer can display the induced voltage effectively.

CsPbBr3 nanoplatelets (NPLs) with different thickness (3-5 monolayers) were synthesized by ligand-assisted reprecipitation at room temperature to study the nonlinear optical absorption properties in the near-infrared-II window. The nonlinear three-photon absorption properties of CsPbBr3 NPLs were investigated by Z-scan technique using a laser with central wavelength of 1030 nm, pulse width of 6 ps and repetition of 25 kHz. The experimental results show that the nonlinear three-photon absorption cross section of CsPbBr3 NPLs is significantly increased due to the enhancement of quantum confinement effect with decreasing the thickness of NPLs. The three-photon absorption cross section of the 3 monolayers NPLs is 4.1 × 10-71 cm6s2photon-2. This study shows that CsPbBr3 NPLs have excellent nonlinear multiphoton absorption properties in the near-infrared-II window, and can be applied in the field of multiphoton fluorescence imaging.

In order to study the effect of gas density on the terahertz wave radiated by multi-color laser-induced air plasma filament, a theoretical model of terahertz （THz） generation from a laser-induced air plasma filament and the subsequent propagation process is established. Based on the model and simulation, the influence of gas density on terahertz radiation is studied. The results show that the gas density will affect the transient current distribution of laser filament and the propagation phase of THz wave, then affect the THz radiation intensity of laser filament, and make the THz radiation energy change nonlinearly with the gas density. The theoretical study is of great significance to the cognition of the physical process of laser filamentation.

In order to effectively enhance and continuously control terahertz wave, we propose a method of modulating the spatial distribution of terahertz wave through external spatial interference. Firstly, we compare the spatial distribution when placing hollow metal waveguides with that when not placing hollow metal waveguides by means of theoretical calculation. The impact on the spatial distribution of terahertz wave is exhibited when changing the propagation path of terahertz wave under external interference. At the same time, we acquire the spatial distribution of terahertz wave which can be continuously regulated by changing the relative position of hollow metal waveguide and laser filament. The results mentioned above provide a new way for continuous regulation of wideband terahertz wave. The results show that the energy intensity of the strongest point in the spatial distribution of THz wave is increased by 5.9 times, which can provide reference for the continuous regulation of broadband terahertz wave.

In this paper, a coupled resonant waveguide based on magnetic photonic crystal has been proposed. The resonant frequency can be controlled by tuning the position of cavities to realize the electromagnetically induced transparency in topological one-way waveguide. The corresponding characteristics are demonstrated based on the finite-difference time-domain method. Our study may provide an approach to realize optical delay and optical switches in the topological waveguide.

Optical microsphere resonator has the advantages of high quality factor (Q), low threshold, and easy to integrate. In order to make better use of microsphere resonator, high Qlaser can be obtained.In this paper, we successfully prepared perylene doped polystyrene microspheres by solvent-nonsolvent fast injection method.By using this method the diameter of the microspheres can be easily adjusted by changing the parameters of experiments. The microspheres have a smooth surface and intact morphological features, which facilitate whispering gallery modes generation in the sphere cavities.Under the femtosecond laser pumping, we can easily obtain the laser signals from either single microsphere or aggregated microspheres, which shows promising applications.

In this paper, a THz device based on single-layer metasurface has been designed to generate near-field plasmonic vortex with shifting functionality for increasing THz communication capacity. Based on the geometric metasurface, the shifting of near-field vortex of the device is simulated by FITD (the finite integration time domain). The corresponding results suggest that position shifting of the field distribution in the whole space can be achieved under the illumination of circularly polarized light. To a certain extent, the kind of functional devices can improve the THz communication capacity and can be used in 6G technology.

Two-photon (2P) stimulated emission depletion (STED) composite microscope has the potential to be widely used in clinical diagnosis of neurological diseases and brain science research. In this paper, based on the research of multi wavelengths selection, multi beams combination, key technical indexes testing research, the integrated development of composite microscopy prototype system and composite imaging are completed. The composite microscope can image the fluorescent labeled samples, which has the functions of red-green two-color fluorescence imaging, 2P green fluorescence imaging and STED super-resolution green fluorescence imaging. In terms of index, the imaging depth is 700 μm, and the resolution of STED imaging is better than 60 nm.

Near-infrared spectroscopy was used to study the mixed solution of transgenic oil/non-transgenic oil. The acquired original spectra were pretreated with multiple scattering correction (MSC), first-order derivative (FD), moving window smoothing (MWS) and savitzky-golay smoothing first-order derivative (SG1). The effects of different pretreatment methods on the discriminant analysis of transgenic oil/non-transgenic oil support vector machine (SVM) modeling were compared. The model after MSC pretreated has the best prediction effect, and the accuracy rate is 91.6%. In order to further improve the accuracy and stability of the model, the successive projections algorithm (SPA) is used to select the characteristic band. We input the 15 feature wavelengths after SPA selection into the SVM, and the prediction accuracy is 98.3%. The experimental results show that the near-infrared transmission spectrum combined with stoichiometry can achieve rapid and non-destructive detection of transgenic oil/non-transgenic oil, not only suitable for the identification of pure genetically modified oils, but also for the identification of non-transgenic oils that are mixed with genetically modified oils.

Single-walled carbon nanotubes are a new generation of transparent conductive materials. They have many special optical, electrical, and mechanical properties and can be widely used in many fields. In this paper, single-walled carbon nanotubes were prepared by arc method and further integrated with polymethyl methacrylate (PMMA) tubular waveguides. The terahertz transmission spectral characteristics of single-walled carbon nanotubes based on tubular waveguides were experimentally and simulated. The results show that single-walled carbon nanotubes can enhance the terahertz resonance of a tubular waveguide and increase the resonance extinction ratio effectively. Graphene and carbon black have little effect on the terahertz transmission spectrum of the tubular waveguide. Single-wall carbon nanotube-assisted integrated devices can be widely used in future terahertz science and technology.

In this paper, we built the optical systems of three age-related human eye models, including the Navarro, the Atchison and the Zapata-Díaz models using the Zemax software, and analyzed the changes of image quality at different ages and different accommodation status. Simulations included retinal image quality evaluations at both 3 mm and 5 mm entrance pupil diameters (EPDs). Accommodation amplitudes ranging from 0.5 D to 2 D were measured in the Navarro and Zapata-Díaz models. Image quality worsens with age or EPD in all the age-related eye models. Besides of the good imaging quality, the Atchison model eye is also consistent with clinical results. Navarro model performs better during accommodation. The results of this study can be valuable for the eye model selection in the field of optometry.

Two-dimensional (2D) transition-metal dichalcogenides have attracted much attention because of its small size and direct band gap properties, which can be used as an excellent luminescent medium in micro-nano optical structures. The 2D materials based micro-nano structure, such as optical microcavity and micro-nano sensor, are always obtained by the transferring method. However, contaminations and damage to the materials are hard to be avoided during material transfer, which will greatly affect the functionality of the structure. Direct growth of the 2D material on the micro/nano structure can solve this problem. WSe2 is deposited directly on the surface of 6 μm-diameter SiO2 sphere cavities by chemical vapor deposition (CVD) method, the compositional characterization of the materials on the microspheres proved that WSe2 was grown on the microspheres, and it was proved that it is feasible to deposit two-dimensional materials on the curved surface by chemical vapor deposition. This 2D material based cavity is expected to be good candidates in high-performance optical sensors and light source devices. It also provides a basis for in-depth study of the exciton characteristics of two-dimensional materials in the high-strain condition induced by curved surface.

The visual odometry uses visual cues to estimate the pose parameters of the camera motion and localize an agent. Existing visual odometry employs a complex process including feature extraction, feature matching/tracking, and motion estimation. The processing is complicated. This paper presents an end-to-end monocular visual odometry by using convolution neural network (CNN). The method modifies a classification CNN into a sequential inter-frame variation CNN. In virtue of the deep learning technique, the method extracts the global inter-frame variation feature of video images, and outputs pose parameters through three full-connection convolution layers. It has been tested in the public KITTI database. The experimental results show the proposed Deep-CNN-VO model can estimate the motion trajectory of the camera and the feasibility of the method is proved. On the basis of simplifying the complex model, the accuracy is improved compared with the traditional visual odometry system.

We design a terahertz monolayer graphene-based modulator using the property of voltage-tunable optical conductivity of graphene. In order to enhance the graphene-terahertz interaction strength, a metal-graphene hybrid structure is used to construct the modulator. The full-wave electromagnetic simulations show that the modulation depth is larger than 90% at 3.5 THz in the reflection operation mode. The prototype device is fabricated with planar semiconductor fabrication processes. The reflection spectra of the device are measured. The experimental data are in good agreement with the simulation results. The method is helpful for realizing high performance terahertz modulators.

The deflector obtains the directional propagation of electromagnetic wave, and plays an important role in sensing and optical communication. The chromatic problem causes the deflection angle varying with wavelength, which limits the application scope of the deflector. In order to achieve achromatic aberration, in this paper, we analyze the physical mechanism of the chromatic aberration and realize achromatic terahertz deflectors using the geometric and resonant compensation phase, which are composed by the all-dielectric metasurface. In addition, the simulations of the achromatic effect are carried out by the finite difference time domain (FDTD) method within a continue frequency range from 0.5 to 1.1 THz.

This paper presents a 16-slot continuous transverse stub (CTS) array antenna that can achieve high gain, high efficiency and lower transmission loss. The antenna can reduce losses and increase radiation efficiency by using series connection stubs. To improve the impedance matching and the directivity, the CTS unit is fed by a combination of a power divider and a radiator. The proposed antenna can exactly operate on dual-frequency. The designed CTS array antenna is simulated by HFSS. The simulated results show that S11 is less than ?10 dB from 75 GHz to 80 GHz and from 85 GHz to 89 GHz. The peak gain reaches 28.6 dB at 78.8 GHz and 28.4 dB at 87.5 GHz. Antenna aperture efficiency is higher than 50% and the main beamwidth of antenna is about 4.4°.

In order to improve the detection sensitivity of Raman spectrometer, a copper-based surface-enhanced Raman scattering film substrate was designed. A series of copper-titanium alloy films were obtained by controlling the magnetron sputtering parameters with Cu40Ti60 alloy target. The copper-based films with different structures were systematically studied. The effects of different sputtering parameters on surface enhanced Raman scattering (SERS） characteristics of the copper-based films were investigated. The optimal sputtering parameters for the preparation of SERS substrates were determined. The copper film obtained after dealloying has a porous structure and can form a high-intensity local electromagnetic field, that is, SERS "hotspots", thereby exhibiting excellent SERS enhancement performance. The substrate is low in cost and good in repeatability by magnetron sputtering, and can achieve sensitive detection and SERS enhancement factor up to 1.8×107. It is one of the ideal choices for high performance SERS substrates and has a high application prospect.

In order to study the influence of interface reflection on terahertz (THz) spectroscopy of double compression tablets, the THz time-domain spectroscopy (THz-TDS) was used to detect the single- and two-layer sand tablets made of different particle sizes, and the THz-TDS were obtained. The results show that the THz peak attenuation coefficient of the unit thickness of the double-layer sample was significantly smaller than that of the single-layer sample. Therefore, a coefficient should be added to study THz spectral response of double-layer samples to eliminate the loss caused by interface reflection of samples, and the coefficient was related to the characteristics of materials.

According to the accuracy requirements of aspheric components in the optical systems, the linear grating polishing trajectory of magnetic compound fluid polishing is designed to polish aspheric compoents. Based on the polishing trajectory and the aspheric equation, the coordinates of each polishing processing point are calculated. The coordinates of the center point of the polishing head are calculated according to each polishing point and the polishing head which is relative to the geometry of the workpiece. The model of high-height error between each polishing point is established, and the variation rule of the surface arch error of workpiece is simulated by the model. According to the variation rule of the surface arch error, the equal arch error control algorithm is used to achieve arch error consistency and improve processing quality.

In order to further reveal the mechanism of ultrasonic vibration assisted grinding, a prediction model of the ultrasonic vibration assisted grinding subsurface damage depth and fracture toughness was established. The single random-shape diamond grit indentation experiments without ultrasonic vibration and ultrasonic vibration assisted grinding experiments were designed. The indentation features of K9 optical glass in the two cases were investigated. A calculation method of equivalent fracture toughness suitable for two cases was proposed. The reliability of the model is verified by ultrasonic vibration assisted grinding experiments. The experimental results show that ultrasonic vibration can effectively increase the resistance of K9 optical glass to fracture, and the prediction model has a good consistency with the test results.