光束特性对声光偏转相干光探测效率的影响

Effect of Beam Characteristic on Detection Efficiency for the Coherent Optical Detection System Based on Acousto-Optic Deflection

相干光探测中,信号光和参考光光斑匹配以及光束特性直接影响探测效率。应用Matlab软件对高斯光斑与平顶光斑的光强分布分别进行仿真,给出两种光斑的数学特征;以声光偏转效应的相干光探测为基础,建立高斯光斑与矩形光斑叠加模型,分析了光斑大小匹配、光轴平移对相干光探测效率的影响。研究结果表明,在保证两束光的准直性及总能量相等的情况下,矩形光斑的能量密度为高斯光斑中心位置的0.8倍时,可获得最佳重叠效率79.6%;非准直状态下信号光与本振光在光敏面的探测效率将会降低,但高斯与矩形混频时在偏离光轴±0.5mm内变化较平缓。

In coherent detection system, the matching of signal beam and local oscillator and the beam characteristic have important effects on the detection efficiency. The light-intensity distributions of Gaussian beam and flattop beam are simulated in Matlab respectively, and the mathematical feature of the two spots are provided. Based on the acousto-optic deflection effect, the effect of spot size matching and signal beam parallel moving along light axis on the coherent detection efficiency is analyzed by building overlay model between Gaussian beam and rectangle beam. The results show that, with the assurance of beam collimation and equivalence in the total energy of two spots, we can get the optimal overlapping efficiency of 79.6 % when the energy density of rectangle spot is 0.8 times as the central energy density of Gaussian spot. The non-collimation of the beams will reduce the detection efficiency when the signal beam is mixed with the local-oscillator beam on the optoelectronic sensor surface. But while rectangle beam is mixed with Gaussian beam, the variation of detection efficiency tends to become gentle when beams deviate from optic axis within ±0.5 mm.