Numerical method and analysis of computational fluid mechanics for photoelectric semiconducting detector

We propose a modified upwind finite difference fractional step scheme for the computational fluid mechanics simulations of a three-dimensional photoelectric semiconductor detector. We obtain the optimal l^2-norm error estimates by using the techniques including the calculus of variations, the energy methods, the induction hypothesis, and a priori estimates. The proposed scheme is successfully applied to the simulation of the photoelectric semiconductor detectors.

Multi-area detection sensitivity calculation model and detection blind areas influence analysis of photoelectric detection target

Multi-element array photoelectric detector is the core devices to form a photoelectric detection target with a large field of view.This photoelectric detection target brings about the problem of uneven detection sensitivity distribution in the detection screen.To improve the uneven detection sensitivity of this photoelectric detection target,this paper analyzes the distribution law of the uneven detection sensitivity of the photoelectric detection target using the multi-element array photoelectric detector,dissects the main factors affecting the detection sensitivity according to the photoelectric detection principle,establishes the calculation model of detection sensitivity of the photoelectric detection target in the different detection areas and proposes a method to improve the detection sensitivity by compensating the gain of each unit photoelectric detector.The analysis of simulation and experimental results show that the proposed method of photoelectric detection target can effectively improve the output signal amplitude of the projectile under the certain detection distance,in particular,the output signal amplitude of the projectile is significantly increased when the projectile passes through the detection blind area.The experimental results are consistent with the simulation results,which verify the effectiveness of the proposed improvement method.

An improved design for Al Ga N solar-blind avalanche photodiodes with enhanced avalanche ionization

To enhance the avalanche ionization, we designed a new separate absorption and multiplication AlGaN solarblind avalanche photodiode （APD） by using a high/low-Al-content AlGaN heterostructure as the multiplication region instead of the conventional AlGaN homogeneous layer. The calculated results show that the designed APD with Al0.3Ga0.7N/Al0.45Ga0.55N heterostructure multiplication region exhibits a 60% higher gain than the conventional APD and a smaller avalanche breakdown voltage due to the use of the low-Al-content Al0.3Ga0.7N which has about a six times higher hole ionization coefficient than the high-Al-content Al0.45Ga0.55N. Meanwhile, the designed APD still remains a good solar-blind characteristic by introducing a quarter-wave A1GaN/A1N distributed Bragg reflectors structure at the bottom of the device.

Miniature optical force levitation system

Optical levitation technology is a new levitation technology for trapping micro/nano-particles.By taking advantage of the mechanical effect of light,it has the characteristics of non-contact and high sensitivity.However,the traditional optical levitation system is large in volume,complex in adjustment,and greatly affected by the external environment.Herein,a miniature optical levitation system based on a laser diode,miniature lenses,and a micro-electro-mechanical system(MEMS) particles cavity is proposed.First,we analyze the output spot characteristics of the laser diode.Being compared the characteristics of different kinds of laser diodes,the type,wavelength,and power of diodes in the levitation system are determined.Then,the micro-particles cavity is fabricated based on the MEMS process.The MEMS process is widely used in the manufacturing of micro-electronic devices because of its advantages of small size,high precision,and easy mass production.The particle cavity processed in this way can not only ensure the advantage of small volume,but also possesses high processing repeatability.The volume of the entire package including the light source,focusing lenses,and MEMS cavity is just Φ10 mm×33 mm,which is the smallest optical levitation system reported,to the best of our knowledge.After the entire levitation system is designed and set up,one silica particle of 10 μm diameter is stably trapped in the atmospheric environment.Finally,the micro-displacement and vibration signal are detected by a four-quadrant photoelectric detector to evaluate the stiffness of the optical levitation system.