两级串联声光可调谐滤波器旁瓣抑制的研究

阐述了偏振依赖的共线型和偏振无关的准共线型声光可调谐滤波器的滤波原理，进而导出了两级滤波的转换特性表达式；通过理论计算说明了两级声光可调谐滤波器能够有效地抑制旁瓣；最后，将两个单级的声光可调谐滤波器级联成两级滤波器，进行了旁瓣抑制的实验.实验结果表明，旁瓣被抑制到-19 dB，并且3 dB带宽也得到一定程度的压窄.关键词：集成光学声光可调谐滤波器旁瓣抑制

Suppression of sidelobe levels using two cascaded single-stage acousto-optic tunable filters

Transfer function of single-stage acousto-optic tunable filter (AOTF) has sidelobes higher than -9 dB, and this large sidelobes level limits AOTF application. In this paper, the sidelobes of two single-stage AOTF's, which are polarization-dependent collinear and polarization-independent quasi-collinear respectively, are investigated, and the transfer function of double-stage filter is obtained. The calculations on single- and double-stage AOTF's have shown that the double-stage device can provide significant improvement in sidelobe suppression. In experiment, two single-stage AOTF's are cascaded, and filtering property of this double-stage device is measured. The experimental results show that the sidelobes of this cascaded AOTF is suppressed to -19dB，and the 3-dB bandwidth is narrowed to some outent.