Optical switch is an important component of integrated optical circuit. In this paper, an on-chip 2×2 directional coupler reconfigurable optical switch based on one kind of chalcogenide phase change materials (Ge2Sb2Se4Te1) used in the L and C bands was proposed. The switch can be switched by changing the phase state. The optical switching device was designed by means of Mode and FDTD Solutions in the simulation software Lumerical. The results showed that the insertion losses (ILs) were more than -0.36 dB and the crosstalks (CTs) were less than -24 dB in the amorphous state of Ge 2Sb2Se4Te1 with a coupling length of 24.9 μm in the band from 1500 nm to 1625 nm. The ILs were more than 0.44 dB and the CTs were less than -30.46 dB in the crystalline state. Multi-physics simulation software COMSOL was used to simulate 532 nm wavelength laser heating Ge 2Sb2Se4Te1. The results showed that a 25 ns short Gaussian pulse with a peak power of 45 mW could transform the material from a crystalline state to an amorphous state. Applying multiple Gaussian pulse arrays with a peak power of 20 mW, a period of 1 μs and a duty cycle of 0.03% could bring it to the crystalline state. Simulation results showed that the designed optical switch can quickly switch optical path in the communication band by laser heating.

With the rapid development of communication technology, the bottleneck appears in the traditional microelectronics industry. More and more people hope that integrated optical circuit can achieve new breakthroughs. Silicon photonics has attracted much attention because of its advantages in materials and manufacturing technology. Among them, the silicon coupler, as an important silicon passive device, is the key to achieve beam coupling and beam splitting on chip. Multimode interference (MMI) couplers are commonly used as integrated optical devices because of their advantages such as low loss, large process tolerance and large bandwidth. In this paper, based on the self-imaging principle of MMI, guided mode propagation analysis (G-MPA) is used to analyze the mode field distribution in MMI, and a taper multimode interference coupler based on 470 μm high resistance silicon wafer in terahertz band is successfully designed. The coupling efficiency of 93.8% is achieved by FDTD simulation and optimization of its parameters.

In traditional information hiding algorithms, embedding rate and image visual quality are mutually restricted, so the relationship between them cannot be balanced. Therefore, in this paper, a high fidelity scheme combining reversible information hiding method and irreversible information hiding method is proposed, which takes advantage of the high embedding rate of the irreversible information hiding method and the high peak signal-to-noise ratio (PSNR) of the reversible information hiding method in the aspect of image visual quality, so as to embed more secret information with less distortion. In addition, the scheme can also find the relative optimal embedding rate, the balance point between the restored image PSNR and the PSNR containing the dense image according to the specific application scene, so as to adapt to different application requirements. Experimental results show that the proposed scheme has higher embedding capacity and better image visual quality than the existing schemes.

In order to improve the accuracy of the eye tracking algorithm and ensure a certain image processing speed, this paper proposes to combine the deformable convolution method to improve the feature distribution extraction level. The fixed-size sampling in the standard convolution makes it difficult for the learning network to adapt to the geometric deformation of the image. In order to solve this limitation, the deformation modeling ability of deformable convolution is used to add a certain offset variable to the position of each sampling point in the convolution kernel. So as to achieve the extraction of potential features, the single frame of the original image is described. According to the current research, the deformable convolution has made preliminary applications in the field of computer vision. After comparing with the advanced eyeball positioning tracking detection network experiment, the accuracy of the deformable convolutional YOLO network can reach 0.685, and the average image processing speed can reach 42 frames per second, which is better than the original YOLO network and the advanced eyeball and location tracking detection network.

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 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.

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 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.

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.

Ni80Cr20 alloy film shows a good neutral transmission in visible light. The quartz crystal sensor in the coating machine has a system error, which results in the actual thickness being different from the standard value. To solve this problem, a new manufacturing method for controlling film thickness of neutral density filters was proposed in this paper, which is bombarded the membrane surface with low energy ion beams. Make the relative error of optical density value is controlled within ±2%, and the absolute error is not more than ±0.01. The error of the thickness of the film is controlled at the atomic layer scale, which meets the requirements of the use of the filter in the spectral system with high precision. It is verified that the neutral density filter still has good optical properties and surface flatness after ion beam etching in this experiment. The technology of ion beam bombardment etching becomes a new and reliable method to control the thin film thickness.

An apparatus for simultaneously inspecting adjacent surfaces defects of thermoelectric cooler (TEC) components based on polarization beam splitting imaging is proposed. The optical design of the apparatus for simultaneously inspecting adjacent surface defects of TEC components is discussed. The proposed apparatus employs polarization beam splitter and polarization camera and meets the conditions of equal-optical-path imaging for both top and side surfaces. The experimental investigations on defects inspection with equal-optical-path polarization imaging system are conducted. The results indicate that the proposed inspection technique with polarization splitting equal-optical-path imaging is capable of simultaneously inspecting the adjacent surfaces defects and the optical apparatus can well meet the performance requirements for inspecting adjacent surfaces defect of TEC components. The inspection resolution can reach 110 lp/mm when equal-optical-path confocal imaging is met, but the inspection resolution reduces to below 45 lp/mm when the defocus is around ±0.20mm. It was noted that the developed technique has obvious advantages of rather good imaging quality, easy adjustment of imaging system, simplified and reliable optical configurations , and improved defect inspection performance.

Ultra-high sensitivity magnetic field measurement is of great scientific and economic significance. Precision measurement of physical quantities using atomic spin effect has become an important means in the field of experimental physics in recent years, among which spin-exchange relaxation free（SERF）atomic magnetometer has attracted much attention because of its ultra-high sensitivity. The alkali metal cell is the sensitive core of SERF atomic magnetometer, and the type of atomic source determines the limit of sensitivity. This paper summarized research results of the SERF atomic magnetometer in accordance with the alkali metal atoms source classification summary, analysis of the research methods, the research progress and the breakthrough obtained in practical application, the development requirement and challenges of SERF atomic magnetometer.

In order to judge the authenticity of the drug and to check the purity of the drug, and to overcome the shortcomings of the long time consuming, sample loss and complicated operation in the current qualitative and quantitative detection of chemical drugs, a fast, quasi determinacy and quantitative method for drug detection based on terahertz spectroscopy is proposed. Based on the terahertz absorption spectrum, the characteristic peak frequency points and the area difference of loratadine and racecadotril were extracted. The qualitative and quantitative detection of the drugs was carried out by using these information. In quantitative detection, stability and accuracy of terahertz spectrum are high. In the establishment of concentration gradient, the linear fitting correlation coefficient reaches 99.8%. Meanwhile, principal component analysis (PCA) was used to detect other drugs. The results showed that the accuracy of qualitative detection was 100%, and the error of quantitative detection was less than 0.01. These results can provide reference for the rapid, accurate and nondestructive testing of the following drugs.