In order to improve the multi-pixel photon counter (MPPC) high-speed detection and improve the photon-number to distinguish features, we use the gated suppression MPPC, and combine the self-balancing and low-pass filtering technology to suppress the capacitive-spike noise of MPPC down to the thermal noise level, realizing the linear extraction and rapid recovery detection of photogenerated avalanche signal. The experiment result shows that the 200 MHz gated MPPC achieves the effective resolution of 14 photons of the 40 MHz repetition frequency lase with the average detected photon number is up to 6.8 per pulse. Compared with the passive suppression mode, the photon number resolution in the 200 MHz sinusoidal gated mode is obviously improved, which provides a reference for high-speed photon-number resolving detection.

In order to understand the transmission effect of the metal spring waveguide on terahertz wave, the transmission characteristics of terahertz wave by springs with different helix spacings have been studied experimentally. The experimental results show that when the pitch is larger as 3.5/4.4 mm (with wire diameter of 0.8 mm, outer diameter of 12 mm and length of 14 cm), the metal spring waveguide can propagate terahertz wave in a larger bandwidth with the additional ability of polarization maintaining. The terahertz transmission bandwidth of metal springs with pitch of 3.5/4.4 mm are both about 0.9 THz, and the lowest transmission loss are about 0.2 cm-1 and 0.27 cm-1 respectively at their peak frequencies. In addition, it has been proved that the terahertz mode was confined inside the air core rather than being guided by the metal helix. The above results are helpful for applications of the metal spring waveguide in the field of terahertz technology.

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.

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.

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.

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.

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.

To improve the sensitivity of optical waveguide sensor based on evanescent wave sensing, a kind of high-refractive-index film coated waveguide optical fiber sensor is proposed by simulation and verified by experiment. In this study, we propose an optical fiber-waveguide-fiber EF sensing platform, which composes of a Ta2O5 coated polymer waveguide sandwiched by two multimode optical fibers, to enhance the intensity of evanescent wave and increase the sensitivity of the sensor. Through simulation results, the Ta2O5 film thickness was optimized. We selected 70 nm, 100 nm and 150 nm thickness for the coating experiments. With the coating thickness of 100 nm, we achieved absorption spectrum limit of detection for Rh B of 1×10-8 g/mL. The sensor has the advantages of low cost, small volume, simple manufacture and high sensitivity, which can be widely used in various fields.

Aiming at the problem that the heat of high-power optical devices and equipment seriously affects their stability, performance and service life, an intelligent and efficient thermoelectric cooling system based on energy feedback is proposed. Based on high precision temperature control realized by the improved incremental proportional integral differential (PID) algorithm, energy recovery mechanism isused to promote the efficiency of the thermoelectric cooler (TEC) refrigeration. Photovoltaic (PV) power management strategy is used through PC monitoring and control of the two groups of efficient storage battery charging and discharging switch. At the same time, Python+PyQt5 is used to build a visual operation graphical interface. The results show that an experimental system for circuit information monitoring and temperature efficient control of TEC device is designed and realized. This study is expected to provide a feasible cooling scheme for high-power optical devices and systems.

In order to solve the problem of communication between the ground and the aircraft, which is called “black barrier”, the vertically polarized terahertz wave is used to realize communication. Using the discharge device to generate plasma to simulate the plasma sheath on the surface of the aircraft, and an all-fiber coupled terahertz time-domain spectrometer is used to generate 0-1 THz waves. This paper studies the transmission characteristics of vertically polarized terahertz waves in uniform non-magnetized plasma with different electron densities from an experimental point of view. The experimental results show that the greater electron density, the faster propagation speed of the vertically polarized terahertz in the plasma; as the electron density increases, the attenuation becomes smaller. This research provides an important experimental reference for realizing the communication interconnection between the ground and the aircraft.

To solve the problems of complex operations, poor repeatability, and contact damage in traditional micro-nano fiber diameter measurement methods, a new measurement system based on machine vision was developed. Firstly, the image was preprocessed and binary segmented in the system, and then the edge of micro-nano fiber was initially located by the Canny edge operator. After that, a sub-pixel detection method based on improved Zernike moment was used to accurately locate the sub-pixel edge. Besides, our system also proposed an algorithm combining Hough transform and the least square method to fit sub-pixel edge points, which improved the measurement accuracy of micro-nano fiber diameters to the nanometer level. The measurement results of micro-nano fiber diameter show that the system can achieve high automation with a measurement error of less than 3.51%, and the running time is 2.671 s. It can be applied to the high-precision and real-time measurement of micro-nano fiber morphology.

Improper treatment of herbicides can cause soil, water and air pollution, and will enter the food chain through the environment, which will affect human health. Atrazine, as a common herbicide, is often detected in the water environment around the world. At present, the main detection methods mainly depend on large instruments, which usually need complex pretreatment, and the skill requirements of operators are high, which is difficult to popularize. With the development of optical materials, terahertz has been expanded to more and more fields, and it is often used to identify the subtle changes of materials. The transmission spectrum of atrazine solution (0, 1, 10, 100, 1000, 2000 ug/L) was detected by terahertz spectroscopy and ultra-material. The transmission spectrum was normalized and analyzed by fitting. The experimental results show that the concentration of atrazine in the range of 1-2124 ug/L can be detected accurately by using terahertz spectroscopy and the super materials, which can effectively improve the sensitivity of pesticide detection.

An off-axis paraboloid with an off-axis angle of 45° and a diameter of 1 inch was used as the sample to compare the difference between the traditional null interferometric measurement results and the non-contact 3D aspheric optical surface shape measurement system Luphoscan. Zemax was used to simulate the influence of the adjustment errors of the six dimensions of the off-axis paraboloid on the measurement results. The expression of off-axis error in the two completely different measurement processes was analyzed, which solved the problem of the availability of Luphoscan measurement results. According to the simulation results, the null test interference optical path structure based on the dynamic interferometer was set up, and the six-dimensional adjustment standard process of the off-axis paraboloid was established, which could quickly eliminate the adjustment error and off-axis quantity error, and the repeatability test results reach the accuracy of pv=0.135λ.