Wenjun He

Polarization properties of a corner-cube retroreflector with three-dimensional polarization ray-tracing calculus

The output polarization states of corner cubes (for both uncoated and metal-coated surfaces) with an input beam of arbitrary polarization state and of arbitrary tilt angle to the cube have been analyzed by using the three-dimensional polarization ray-tracing matrix method. The diattenuation and retardance of the corner-cube retroreflector (CCR) for all six different ray paths are calculated, and the relationships to the tilt angle and the tilt orientation angle are shown. When the tilt angle is large, hollow metal-coated CCR is more appropriate than solid metal-coated CCR for the case that the polarization states of output beam should be controlled.

Optoelectronic measurement system for testing the optical parameters of infrared seeker

We propose an optoelectronic measurement system for testing the optical parameters of infrared seeker, such as the position of the image plane, the size of the diffused spot, and the diameter of the scanning circle. The measurement method and operating principle of the optoelectronic measurement system have been introduced. The source of the stray light in the optoelectronic measurement system have been analyzed by using FRED software, and the stray light have been restricted effectively by a co-centered mica plate which closes to the substrate of pinhole. Experimental results show that the test error for the size of the diffused spot is less than ±0.01 mm, the test errors for the position of the image plane and the diameter of the scanning circle are less than ±0.02 mm.

Polarization-independent variable optical attenuator based on rhombic prism

An optical attenuator with special performances, such as wide spectrum, high precision, polarization-independent, and lager dynamic range, is the key device for testing the communicat ion link performance in free-space laser communicat ion systems. We propose a polarizat ion-independent variable optical attenuator based on rhombic prism. Two rhombic prisms are used to balance the polarization aberrat ions, and the incident surfaces of the rhombic prisms are perpendicular to each other. We control the incident angle of the rays, which incident the reflected surfaces of the rhombic prisms, between the Brewster angle and the critical angle, then the attenuation coefficient of the attenuator can be changed. The results of theoretical analysis and numerical simulation show that the designed attenuator is polarization independent, the wavelength range is from 790nm to 1550nm, the dynamic range of attenuation coefficient is from -40 dB to -3 dB, and the wavefront aberration is less than  /20@974nm.

Design method of coaxial reflex hollow beam generator

In view of the light energy loss in central obscuration of coaxial reflex optical system, the design method of a kind of hollow beam generator is introduced. First of all, according to the geometrical parameter and obscuration ratio of front-end coaxial reflex optical system, calculate the required physical dimension of hollow beam, and get the beam expanding rate of the hollow beam generator according to the parameters of the light source. Choose the better enlargement ratio of initial expanding system using the relational expression of beam expanding rate and beam expanding rate of initial system; the traditional design method of the reflex optical system is used to design the initial optical system, and then the position of rotation axis of the hollow beam generator can be obtained through the rotation axis translation formula. Intercept the initial system bus bar using the rotation axis after the translation, and rotate the bus bar around the rotation axis for 360°, so that two working faces of the hollow beam generator can be got. The hollow beam generator designed by this method can get the hollow beam that matches the front-end coaxial reflex optical system, improving the energy utilization ratio of beam and effectively reducing the back scattering of transmission system.

The principle of space coherent laser communication based on Costas phase-locked loop

The space coherent laser communication is a very potential mean for high-speed laser communication in the future, because the excellent receiver sensitivities can be achieved by coherent detection techniques. The best coherent receiver sensitivity amounts to -59.4dBm at a data rate of 10Gbit/s and a bit error rate of 10-9, which is obtained with phase-shift keying modulation in combination with homodyne detection. In this paper, we investigated optical homodyne detection based on Costas phase-locked loop in the space coherent laser communication system. We obtain optimum loop bandwidth of Costas phase-locked loop and the maximum permissible laser line width based on Costas phase locked loop.

Research on optimum local oscillator laser power of the space coherentlaser communication

The space coherent laser communication is a very potential and attractive mean as it allows higher speed communication between satellites. The space coherent laser communication makes use of local oscillator laser power to improve the power of received optical signal by mixing local oscillator laser and optical signal together. However, the power of the local laser oscillator can not be increased infinitely, too large but reduces the detection sensitivity. In this paper, starting from the principle of the signal-to-noise ratio of the space coherent laser communication, we found the optimum local oscillator laser power was 28.174mw, under the condition of the selected photodetector specific parameters. It is a great significant for high detection sensitivity and low data error of the actual coherent detection system.