Abstract:We propose and make a compact yellow-orange laser of the Nd-doped yttrium vanadate (Nd:YVO4)/periodically poled Mg-doped lithium niobate (PPMgLN) module by Raman frequency-doubling at 589 nm. By reasonably designing the size of the Nd:YVO4 and 5 mol% PPMgLN crystals, cavity length and coating parameter, a compact 589 nm laser module with a total size of 3 mm×10 mm×1.5 mm is fabricated. In the laser module, the input surface of Nd:YVO4 crystal is end-pumped by an 808 nm laser diode (LD). Under the effect of linear resonant cavity structure, the output surface of PPMgLN crystal with a period of 9.48 μm generates 589 nm yellow-orange light. The experimental results show that the maximum output power at 589 nm is 390 mW at the pump power of 3 W with the optical-optical conversion efficiency of 13% and the stability of the output power is less than 2% within 3 h.

Abstract:Convolutional neural networks (CNNs) require a lot of multiplication and addition operations completed by traditional electrical multipliers, leading to high power consumption and limited speed. Here, a silicon waveguide-based wavelength division multiplexing (WDM) architecture for CNN is optimized with high energy efficiency Fano resonator. Coupling of T-waveguide and micro-ring resonator generates Fano resonance with small half-width, which can significantly reduce the modulator power consumption. Insulator dataset from state grid is used to test Fano resonance modulator-based CNNs. The results show that accuracy for insulator defect recognition reaches 99.27% with much lower power consumption. Obviously, our optimized photonic integration architecture for CNNs has broad potential for the artificial intelligence hardware platform.

Abstract:An optical fiber sensor composed of a dislocation Mach-Zehnder interferometer (MZI) cascaded with a fiber Bragg grating (FBG) is proposed, and it is used to monitor the electrochemical corrosion of metals in experiments. The dislocation interferometer is composed of two segments of single-mode fiber (SMF) and one segment of dislocation SMF. The contact surface is increased between the fiber and the environment, which helps to improve the interference sensitivity. The relationship between the dislocation amount and the refractive index sensitivity of the interferometer is discussed through simulation. In the experiment, the sensitivity of the interferometer reaches more than 10 000 nm/RIU, and the monitoring of metal electrochemical corrosion is also realized in 3.5% NaCl solution. The proposed measurement scheme has the advantages of small structure, low cost and high sensitivity. It has good prospects in chemical reaction monitoring.

Abstract:Avalanche photodiodes (APDs) have high output and high stability requirements for bias power in Geiger mode. This paper designs an APD with high boost ratio, high precision, low temperature drift, small size, and low power. Bias power supply, this module uses switching chip IC and flyback transformer to achieve high step-up ratio, realizes precise output control through precision operational amplifier and T-type resistor feedback network, and designs appropriate compensation network to improve system stability. The size of the module is 2.5 cm×2.5 cm, the output voltage is adjustable from 0 to 450 V, and the maximum ripple does not exceed 5.4 mV. By changing the control voltage, any type of APD in Geiger mode can be biased, and the maximum deviation of the bias voltage does not exceed 0.5%.

Abstract:In this paper, a novel dual-band photonic band gap (PBG) structure was proposed and applied to a dual-band microstrip antenna. The antenna resonates at 1.267 THz and 1.502 THz, exhibiting reflection coefficients of −58.177 dB and −49.462 dB, and gains of 3.173 dBi and 5.232 dBi, respectively. Compared with the microstrip antenna based on the homogeneous silicon substrate, the designed dual-band antenna based on the novel PBG structure shows improved impedance matching, radiation efficiency, and gain. The paper simulated and analyzed the impacts of different filling dielectric materials and the variations of dimensions, position, period, and corrugation depths of the dual-band PBG structure on the resonances of the antenna. It is expected that the proposed novel dual-band PBG structure has great application potentials, and such cancer diagnosis is done by utilizing the radiation characteristics of the antenna.

Abstract:WO3/Au composite film electrode was prepared by hydrothermal combined electrodeposition method. The samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), and the results showed that WO3/Au composite film was synthesized. Electrochemical and spectral measurements were carried out to obtain the electrochromic response time, reversibility, coloration efficiency (CE) and transmittance of the WO3/Au composite film. The photoelectrochemical properties of the samples were characterized by measuring photocurrent and photocatalytic degradation efficiency. The results show that compared with pure WO3 nanoblocks, WO3/Au composite film improves the electrochromic property, photocurrent and photoelectric catalysis activity. Among them, WO3/Au composite film prepared by depositing Au nanoparticles in 80 s showed the highest electrochromic property, photocurrent and photoelectric catalysis activity. Meanwhile, compared with direct photocatalysis (DP) and electrocatalysis (EC), the photoelectrocatalysis (PEC) activity of the composite film is the highest.

Abstract:This paper demonstrated a Q-switched erbium-doped fiber laser (EDFL) using an organic saturable absorber (SA) based on 8-HQCdCl2H2O material. The organic thin film was prepared using the casting process. The proposed Q-switched EDFL has a maximum repetition rate of 143 kHz, minimum pulse duration of 1.85 µs and the highest pulse energy of 167 nJ. The Q-switched peak laser was at a central wavelength of 1 531 nm with a 3 dB bandwidth of 3.52 nm and power intensity of 2.64 dBm.

Abstract:Aiming at the problem of poor accuracy consistency of large sections’ docking assembly, an automatic docking method using multiple laser trackers to measure the position and posture of the docking sections in real time was proposed. In the solution of the pose of the docking section, real-time pose measurement of the docking section was realized by establishing a global coordinate system and a coordinate fusion method of three or more laser trackers. In the automatic control of the docking process, the real-time communication protocol and the circular negative feedback control strategy of measurement-adjustment-re-measurement are adopted, and the fully-automated docking of large sections is realized. Finally, an experimental verification system was set up, and the docking of the large-scale section reduction models was realized under the requirements of docking accuracy, and the effectiveness of the automatic docking scheme was successfully verified.

Abstract:Light emitting diode (LED) light source degradation detection and lifetime evaluation usually use the data of light flux change as a basis, but the process of light flux measurement is complicated and tedious, requiring the use of an integrating sphere, and cannot be performed online. This is unfriendly to the detection of machine vision light sources used in production lines. To address this problem, this paper proposes and designs a method for online detection and lifetime evaluation of light sources by using a mini spectrometer to detect the intensity of light sources online, and evaluates the light degradation and lifetime of light sources based on the changes in light intensity during use. This determines whether the light source needs to be adjusted or replaced, avoiding misjudgment or missed judgment in production detection due to light source degradation. The experiment was conducted on LED under high-temperature accelerated aging. The light intensity data after aging was fitted by an acceleration and life evaluation model, and the fitting result showed that the error of life evaluation by this method was 8.37%. As a comparison, this paper also detects the changes in light flux of light sources during the experiment, and the average error between the decay of light intensity and the decay of light flux was only 0.102%. It has been validated that the error in evaluating the lifetime of light sources using this method is 10.71%, and the accuracy of the evaluation is about 90%. The results show that the method is accurate, reliable, and can be used as a basis for online detection and evaluation of LED light source degradation.

Abstract:Aiming at the accuracy challenge in obstacle detection for autonomous driving, we propose an improved you only look once X-S (YOLOX-S) model based on swin transformer-tiny YOLOX-S (ST-YOLOX-S) for obstacle detection, which could detect multiple targets, including people, cars, bicycles, motorcycles, and buses. Our method mainly comprises two aspects as follows. To improve the capability of local feature extraction and then obtain more accurate detection for obstacles under real-world vehicle conditions, the existing backbone of YOLOX-S is replaced with the swin transformer-tiny backbone. We reduced the number of channels between the swin transformer and path aggregation-feature pyramid network (PA-FPN) from [96, 192, 384, 768] to [192, 384, 768], to decrease the computational cost and then make the swin transformer-tiny more compatible with the PA-FPN. Conclusively, on the popular COCO dataset, the proposed ST-YOLOX-S improves the detection mean average precision (mAP) by 6.1% when compared with YOLOX-S. Among the five types of obstacles that appear in simulated actual vehicle conditions, our ST-YOLOX-S also achieves superior performance compared to YOLOX-S. Furthermore, our method achieves significant performance over the YOLOv3 on obstacle detection, which shows the effectiveness of the proposed algorithm.