Consistency Of Laser Coherent Synthesis Of Neutron Beam

The brightness of laser beam is an important parameter in industry and directed energy applications. A single laser emitter is typically limited in output power due to thermal effects, nonlinear effects, damage of gain medium and other effects. In order to improve the brightness of the laser beam, coherent beam combination technology has been paid more and more attention. The sub-beams’beam quality and wavefront aberration which would affect the quality of beam combination had been studied widely. In the experiment of coherent beam combination, we found that the sub-beams’intensity and wavefront errors different from the ideal beam will reduce the beam combining efficiency and quality. On the other side, the inconsistency between the sub-beams may be another factor which would reduce combining efficiency or synthetic beam quality. This paper attempts to carry out some exploratory research from a new perspective.First, the paper analyzes the basic principle of tiled-aperture coherent beam combination and filled-aperture coherent beam combination, and finds that it’s a necessary condition for sub-beams to meet each other. And the overall overlapping degree or consistency of sub-beams is the essence factor that affects the result of coherent beam combination. For example, when the beam cross section, intensity distribution and the phase in the beam combine region satisfies consistency conditions, we can get the best results and high combining efficiency.Then, the consistency of sub-beams in tiled aperture system has been studied in this paper. In tiled-aperture system, all the sub-beams tiled in an aperture. When the beams transfer to far field, they meet and overlap. The parameters in near field such as intensity distribution, optical axis and phase errors will affect the far field spot overlap degree. The areas of constructive/destructive interference are changed by inconsistency of far field spots’ position, intensity distribution and phase. Then the beam quality and the combining efficiency will change for the areas of constructive/destructive interference. Also, in the debugging process of beam synthesis device, we should ensure the consistency of axis, divergence angle parameters and phase. It’s a difficult work to detect these parameters accurately and conveniently. In this paper, the shearing plate is put forward to make sure these parameters consistent. The Shearing interference principle was studied by the way of numerical simulation and applied in the experiments. A coherent combining scheme for four slab laser is proposed. The sub-beam’s power is hundreds watts range. According to the experiment, we get the date which reflecting the result of beam combining and beam quality and verified the technology of tiled-aperture coherence beam combining. The combining effect can reach80percent of its ideal value, the beam quality BQ goes to1.26. The energy can reach51%in the Airy spot of the total energy.Third, the consistency of sub-beams in filled-aperture beam combine system has been studied. In this system, the sub-beams meet each other in near field through the beam combiner. At one output end, two sub-beams constructive interference, while two sub-beams destructive interference at the other end. The influence to the beam combining efficiency because of sub-beams’ consistency had been studied by theoretical research and numerical simulation. From the theoretical research and simulation, we get the analytic formulas and numerical curve. The paper also takes a filled-aperture coherent beam combine experiment which beam combiner is semi-transparent mirror. And in the phase locked loop system, the output light intensity is stabled, and the combining efficiency could be more than95%. The experiment verifies the feasibility of this technology.Finally, the research work is summarized. High power laser coherent beam combine technology research was prospected.