As the most representative directed energy carrier, the laser can be utilized for high-power and long-distance wireless power transmission. Conventionally, the wireless laser power transmission requires complex and expansive acquisition, tracking and pointing (ATP) system to deliver the laser to the receiver. Recently, there emerges the novel resonant laser power transmission technology. With the laser resonating between the power transmitter and the receiver, the beam is directed to the receivers automatically, without the necessity of the ATP system. The strengths and the weaknesses of the two different technologies are analyzed and compared, and the development is prospected. The development of alignment-free laser, which is the essential of the resonant beam wireless laser power transmission approach, is also summarized.

The traditional photoelectric dew-point hygrometer has some problems in the measuring process, such as unstable measuring pressure, unclean measured gas, easy contamination of dew point mirror surface and insufficient display, which reduce the measuring accuracy and limit the scope of application. The HP-U dew-point hygrometer is improved on the basis of the original photoelectric dew-point hygrometer, so that the measurement accuracy is higher, the application range is wider, and the display data is more comprehensive. Three display HP-U dew point hygrometer is equipped with gas detection chamber to eliminate the influence of gas pressure fluctuation on dew point temperature. The contrast photoelectric system is used to eliminate the influence of gas pollution impurities, and the measurement accuracy is improved. The dew-point mirror automatic cleaning device is set to clean the dirt and impurities on the surface of the dew-point mirror in time to ensure that the mirror is clean and improve the measurement accuracy. The measured gas temperature display instrument, dew point temperature display instrument, relative humidity display instrument are composed of three display system, which can read measurement data in real time, save time and effort, is simple and convenient. The nitrogen system is set up to blow the detected gas out of the gas detection room in time to ensure that the gas detection room is clean and free from pollution. Three display HP-U dew-point hygrometer plays an active role in promoting the development of photoelectric dew-point hygrometer.

An optical system of laser dazzler is designed. The optical system is composed of a collimating system and a zoom beam expansion system, which can continuously adjust the divergence angle of the output beam of the laser dazzler. The output laser wavelength of the fiber laser is 525 nm, the numerical aperture is 0.15, and the luminous surface is 100 μm×25 μm. After being collimated by the collimating lens, and then emitted by the zoom beam expansion system, the glare distance of 100~200 m is achieved, and the static glare area of the laser is 1 m×0.24 m. The narrow edge direction of the glare surface is scanned through the galvanometer to make the laser glare area of the above glare distance reach 1 m×5 m, which is applicable to the laser glare requirements of passes and passageways. The dazzling surface produced by the optical system outgoing beam has a small fluctuation in laser power density, which can effectively maintain the dazzling effect. The total length of the optical system is 63 mm, the structure is simple, it is conducive to engineering, and the application prospect is broad.

In order to optimize the user experience and meet the needs of convenient portability and high imaging quality of virtual reality displays, the reverse optical path design method is used, with software simulation and theory to design a virtual reality (VR) display system with aspheric structure, and image quality evaluation and tolerance analysis are conducted. Each monocular field of view has 4 aspheric lenses with a field of view angle of 90°, a pupil diameter of 6 mm, a pupil distance of 12.55 mm, a modulation transfer function greater than 0.25 at the Nyquist frequency (14 lp/mm), and a maximum distortion of 12.23%. The structure designed is compact, has high image quality, which met the design requirements of VR glasses-mounted display.

Mid infrared supercontinuum light source has the characteristics of ultra-wide spectrum, high coherence and high brightness, which is widely used in many fields. However, in the process of supercontinuum generation, modulation instability causes the transfer of energy between different fundamental solitons to form optical rogue waves. It is a low probability event with ultra-high intensity, great red shift and produced at the wavelength of supercontinuum spectrum. Its generation seriously affects the performance of supercontinuum spectrum. Therefore, the research on optical rogue wave control has become a hot topic. Because the dispersion oscillating fiber has flexible and adjustable dispersion and nonlinearity, which can effectively control the generation of optical rogue wave. Therefore, the effect of dispersion oscillating fiber on optical rogue wave in mid infrared supercontinuum spectrum is mainly studied.

A mid-infrared gas detection system based on barium gallium selenide crystal (BaGa4Se7) optical parametric oscillation (OPO) technology is developed. The BaGa4Se7 OPO pumped by a commercial 1 064 nm pulsed laser is used to achieve 3~8 μm tunable output. The system is further used to detect air, carbon dioxide and exhaled gas, and the change of mid-infrared energy near 4.2 μm is studied when the temperature and pressure changed. In addition to the above gas detection, the system can also be used to achieve more gas detection, calibration, as well as biological, environmental and other aspects of the research.

In this work, fiber Bragg gratings (FBGs) are inscribed in seven-core fiber (SCF) based on phase mask technology. The temperature sensing characteristics of seven-core fiber Bragg gratings (FBGs) at room temperature and low temperature are studied by experiments. The results show that the sensor has a temperature sensitivity of 9.98 pm/℃ and a linearity of 0.999 44 in the normal temperature range of 30 ℃~80 ℃. In the low temperature range of -60 ℃~20 ℃, the sensor has a temperature sensitivity of 8.77 pm/℃ and a linearity of 0.997 51. It can be seen that seven-core fiber Bragg grating has relatively stable response characteristics at both normal and low temperatures, but when the temperature decreases, the sensitivity decreases and the linearity becomes worse. The research results have reference value for the research of temperature sensing based on fiber Bragg grating.

A humidity sensor is proposed by coating aluminum oxide and polyvinyl alcohol film on the etched fiber Bragg grating by pulling technique. The strain generated by the hydro-philicity of the humidity sensitive film induces the central wavelength of fiber Bragg grating shifting, thus the environmental humidity monitoring is realized. In the experiment, the diameter of fiber Bragg grating is etched to 50 μm by hydrofluoric acid, the mixture ratio of aluminum oxide and polyvinyl alcohol solution is 9:1 and the coating thickness of humidity sensitive film is 80 μm. The experimental results show that the humidity sensitivity is 6 pm/% RH in the humidity range of 40% RH-58% RH, the humidity sensitivity is 32.3 pm/% RH in the humidity range of 58% RH-70% RH, the temperature sensitivity of the sensor is 14.2 pm/°C in the temperature range of 25~70 °C. The instability of the sensor is 0.0745% RH, and the human breathing testing shows that the response time and recovery time of the sensor are 1.94 s and 5.19 s, respectively. The sensor has advantages of simple fabrication, high humidity sensitivity, good stability, which indicates it has application potential.

In response to the initial YOLOv5 target detection algorithm's problems of inadequate extraction of defect features in complex targets, imprecise localization, low detection accuracy and high miss detection rate, an improved YOLOv5 steel surface defect detection algorithm is proposed, in which the anchor frame is calculated with the K-Means++ algorithm for anchor frame selection, so that the randomly selected clustering center tends to the global optimal solution as much as possible and the prediction frame is more accurate. The CBAM attention mechanism is added to give higher weights to the defects in complex images and enhance the attention to key information. The results after the experimental comparison show that the improved YOLOv5 algorithm has better detection performance.

In order to establish the influence relationship between surface roughness parameters and surface gloss, starting from the measurement method and principle of the latter, the extinction mechanism of rough surface is analyzed in detail, the glossiness calculation method is introduced, and the influence of the coherence length and the mean square deviation of surface height fluctuation on surface gloss is investigated. The results show that the surface gloss decreases rapidly as the mean square deviation of surface height fluctuation increasing in the range less than the wavelength. With the increasing of coherent length and incident angle, the surface gloss increases accordingly. The relevant methods and conclusions are of fundamental significance for the subsequent establishment of the relationship between the gloss and the fine structure characteristics of the surface, so as to achieve the adjustment of the gloss by controlling the fine structure.

According to the market demands of developing low-cost optical fiber pressure and flow meters, an effective method of integrating a limited number of ordinary narrow-band light sources into a small wide-band light source is proposed. Research results show that multiple narrow-band light sources with different wavelengths, which meet certain conditions, can be changed into a small broadband light source by coupling multiple optical fiber couplers. By adjusting the internal current of the narrow-band light source and changing the output light intensity, the spectral flatness of the small-scale broadband light source can be effectively improved. With the help of mathematical algorithm, the judgment basis for the optimal spectral quality of the small broadband light source is proposed theoretically. By using the spline fitting function, the program can be written, and the output light intensity of a single light source can be automatically adjusted by controlling the current effectively. Research results show that the small broadband light source developed by this new technology has the characteristics of low manufacturing cost, small volume, high spectral flatness and adjustable intensity, and the spectral width can reach 2~3 nm. The simulation testing shows that the proposed method is effective.

With the continuous improvement of optical prism manufacturing level, more and more cube and right angle prisms with second order accuracy are used in optical systems. The introduced cube glued prism is an optical part of our company, see Fig.1, the overall dimension of the glued prism is 54×54×54 mm, and the bonding drawing requires double aberration S≤10″,in order to meet the technical requirements of double aberration of the glued prism, the first and second parallel aberration of a single right angle prism should be controlled within 5″. Through the application of relevant process control methods and separator polishing precision machining technology, the machining accuracy and production efficiency of parts are effectively guaranteed.