基于多路复用体全息光栅的角度放大器设计

为设计基于多路复用体全息光栅的角度放大器, 建立了多路复用角度放大器(MAM)模型, 从效率均衡性和角度分布均匀性两个方面归纳了其设计规则; 研究了光刻过程中的误差对MAM性能的影响; 分析了实际发散光束对MAM性能的影响. 研究表明:控制光栅空间频率和光栅倾斜角可以实现需要的MAM角度分布, 控制光栅厚度和折射率调制深度可以实现MAM最佳衍射效率; MAM最大复用路数不超过10路; 增大光栅倾角或者记录光与工作光波长之比有利于抑制参考光角度误差带来的MAM出射角分布误差, 减小光栅厚度有利于抑制厚度误差与折射率调制深度误差对衍射效率的影响; 当远场发散角大于光栅角半宽时, 最佳衍射效率下降到50%以下且角度选择曲线失去局部最小值; 增大空间频率或者光栅厚度可以减小所需的折射率调制深度, 增多MAM可复用路数, 但是不利于效率均衡性设计和抑制发散光束的影响.

Design of angular magnifier based on multiplexed volume holographic grating

In order to design an angular magnifier based on multiplexed volume holographic grating, the physical model of multiplexed angular magnifier (MAM) is established. The design principle is summarized from two aspects, namely, uniform angular distribution and optimum diffraction efficiency. The effect of production error on MAM is studied. The effect of beam divergence on the performance of MAM is investigated. The results show that the desired angular distribution of MAM is achieved by controlling the spatial frequency and the tilted angle of the grating while the optimum diffraction efficiency is achieved by controlling the thickness and the amplitude of refractive index modulation of the gratings. The 10 VHGs can be multiplexed in the MAM at most. The raising of the grating tilted angle or the ratio between the wavelength of recording beam and working beam can weaken the effect of angular error of reference beam on the output angle distribution of MAM, and the reducing of the thickness is beneficial for reducing the effect of error of thickness and refractive index modulation on diffraction efficiency. When the beam divergence is greater than the angular half width, the optimum diffraction efficiency falls down to 50% or lower and the local minimum values disappear. The raising of the spatial frequency or thickness of the gratings can reduce the desired amplitude of refractive index modulation and multiplex more VHGs, but is not beneficial for achieving uniform diffraction efficiency distribution and weakening the effect of divergent beam.