With urgent demand for an integrated information network and development of free-space laser communication technology, research on high-rate laser communication networking technology is vital. This study analyzed the technical difficulties related to space laser communication networking and proposed a laser communication networking solution. A wide-angle beam expander and dual-rotating prism group were incorporated into a multiaccess optical laser communication antenna. The wide-angle beam expander collects signal light from different directions; the dual-rotating prism group tracks different targets simultaneously. This paper presents an overall scheme allowing multiaccess free-space laser communications based on the optical antenna described and the associated relay optics and transceiver subsystems.
It is urgent to tracking and making a catalog for space debris, since they are such serious threats to spacecraft. Space-based detection possess a great of development potential for its low energy consumption, high precision and miniaturization and other features. This paper discussed the capability of space-based combined system that is laser ranging and imaging integrated communication system. With the diameter of 15cm of space debris, the limit distance of communication, ranging and imaging system are discussed. The result shows that the limit distance of communication and energy imaging is longer, and the main factor to limit the distance is ranging and diffraction limit of imaging system.
A mid-infrared optical parametric oscillator (OPO) with an idler wavelength of 3.85 μm at a repetition rate of 200 kHz is presented, and a high-repetition-rate electro-optic (EO) Q-switched Nd∶GdVO 4 laser with a double-crystal RbTiOPO 4 EO modulator is used as the pump source. The OPO is designed as an extracavity singly resonant optical parametric oscillator. The threshold value of the OPO system is only 1.3 W at 1.06 μm. When the MgO: periodically poled lithium niobate (MgO: PPLN) crystal is operated at 90°C and the pump power is 10.5 W with a repetition of 200 kHz, a maximum average output power of 1.82 W at idler wavelength of 3.85 μm and pulse width of 14.3 ns are obtained. The slope efficiency of the 3.85-μm laser with respect to the pump laser is 21.3%. The M 2 factors of the 3.85-μm laser are 1.84 and 1.76 in the parallel and perpendicular directions, respectively. The mid-infrared tunability of 3.7 to 3.9 μm can be achieved by adjusting the temperature of MgO∶PPLN crystal from 210 to 35°C.
266nm UV laser has a wide range of applications in various fields by its advantages in high single photon energy and
high resolution, which also has a development gradually moving in the direction of high power and high conversion
efficiency. In the process of high-power laser frequency doubling, BBO crystal inevitably absorbs part of fundamental
light power and frequency doubled light power, it induced the temperature rise along the direction of radiation in crystal
and destroyed the phase-matching conditions of BBO crystal that lead to phase mismatching. In order to improve
harmonic conversion efficiency as well as reduce the influence of output power and beam quality caused by phase
mismatching, in this paper we analyzed the process of phase mismatching, established the thermal-induced phase
mismatching model by using analytical expression of the nonlinear crystal temperature field equation which has been
given, and the three-dimensional phase mismatching distribution were obtained. There are three major contributions in
the paper. Firstly, the working process of the nonlinear crystal was analyzed, and the physical and mathematical models
of temperature distributions were established, and the BBO crystal three-dimensional temperature distributions were also
obtained. Secondly, a variety of factors that affect the temperature distributions within the BBO crystal were summarized.
For different 532nm waist radius and 532nm input power, they were numerical simulated use of MATLAB. Finally,
combined with the above analysis, the physical and mathematical models of phase mismatching caused by energy
absorption of BBO in forth harmonics generation were established, the phase mismatching distributions in the crystal
were simulated as well, especially the changes to phase mismatching distributions with different parameter were
analyzed. Combination of the multiplier theory, the influence of phase mismatching on frequency doubling conversion
efficiency was analyzed. The results indicate that the physical model which established in this paper can explain the
physical reasons in high-power laser frequency doubling system very well, such as the reduce in conversion efficiency
and output power and beam quality. All research results play instructive effect at the improvement of conversion
efficiency and the compensation for the phase mismatching for further research.