Research On Multi-wavelength Laser Beam Combination Technology And Thermal Effect

High power and large aperture laser transmitter system is the hot and frontier research problem in the industry and military field. In order to meet the usage requirements of optoelectric apparatus, this paper proposes a laser beam combination transmitter method with multi-band and high power laser. It is a system combines with tracking and emission. After the laser on each band has been incoherent beam combination, the transmitter system will emission in the way of co-aperture. This system is a new laser transmitter method which has minimized weight, simple structure and well maneuvering performance and it can adapt to general operational requirements in different environment. In the high power laser system, the thermal effect produced by optical elements will lead to a quality reduction of the laser beam. In this paper, it takes the finite element software and Matlab software as tools, and uses the thermal/structural/optical integrated method for researching the aspects on beam combination system, laser thermal effect, environmental temperature thermal effect, and beam quality in the far field, etc.In the stage of beam combination design, firstly it studies different kind of incoherent beam combination methods, and then determines to take the way of band beam combination for solving all three band laser beam combination. The substrate of beam combination mirror will choose well infrared optical material Zn Se. Secondly, we derive the combination formula for laser and the formula for covering the object in far field. It uses Zemax software to simulate beam combination optical path combined with the accuracy formulas of beam combination, and offers support for selecting the key parameter of beam combination accordingly. Finally, it introduces optical path monitoring and correction system supporting with beam combination system. And it makes design analysis on the geometrical parameter of beam combination mirror and the mechanism of beam combination system.The Zn Se infrared material is sensitive to heat. The beam combination mirror with Zn Se material not only has surface distortion, but also has refractive index change due to the temperature difference. So this paper takes advantage of Thermal/structural/optical integrated method to make thermal-optical analysis for beam combination mirror and beam combination system. Firstly it builds the temperature rise and structural analysis model for beam combination mirror in different load cases. On this condition, it calculates the temperature distribution and surface deformation in different boundary conditions and load cases using the finite element software. The effects of convective heat transfer coefficient and frame heat conduction on numerical accuracy are studied, and the effects of different beam size and different beam combination mirror thickness on the thermal distortion are also simulated. Thus in this paper, it summarizes the thermal distortion rule of beam combination mirror. Secondly, it makes a thermal-optical analysis about beam combination system in practical application. It makes a concrete analysis about wavefront distortion due to the laser bias. It also calcculates the laser wavefront distortion in each band within 90 s of laser running, and the effect of temperature on far field laser beam quality in different environments is calculated. Finally, it proposes a temperature control method for beam combination. It will take the heat accumulation away in the intermissions of laser running.At last, it establishes the experimental platform of laser thermal effect and test platform of laser power in the far field, Firstly, the platforms test the laser irradiation thermal effect of beam combination mirror. The results shows that the results of thermal effect experiment are in good accordance with the results of simulation calculation. On the issues of high power laser systems are hard to test, it can be verified by using alternative light sources with low power laser and simulating calculated method. The experimental platform of far field laser makes use of the thermal imager-power meter to test the impact of laser system thermal effect on the far field laser, the thermal effect caused the decreasing of the far field laser power, but due to the data fluctuation of the test, it is also need further reduce the error.