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为在能量天平动圈位移测量中实现大范围纳米精度法-珀干涉绝对距离测量,提出了声光移频器双通道配置,实现了调谐范围为200 MHz的可调谐频差.通过分析声光移频器调制带宽与衍射效率的平衡与入射光束聚焦透镜的关系,确定透镜的最佳焦距范围;利用零级光斑分布特点准确定位入射光束,保证一级衍射光束质量.声光移频器在调制带宽内的实验单通道和双通道峰值衍射效率分别为79.54%,61.41%;声光移频器双通道配置输出的一级衍射光束与入射本征光束的拍频范围为440—640 MHz,是单通道调制带宽输出220—320 MHz的两倍,信噪比好.理论分析表明,声光移频器双通道配置方法实现的可调谐频差可测量腔长变化范围约为53 mm的折叠法-珀腔.
In order to realize the large-scale measurement of the absolute value of the nanometer-precision interferometer in the kinematic displacement measurement of the energy balance, a dual-channel configuration of the acousto-optic frequency shifter is proposed, which achieves a tunable frequency difference of 200 MHz in the tuning range. The relationship between the modulation bandwidth and the diffraction efficiency of the frequency shifter and the focusing lens of the incident beam is determined to determine the optimal focal length of the lens and the position of the incident beam is accurately positioned by using the distribution characteristics of zero order spot to ensure the quality of the first order diffracted beam. The experimental single-channel and dual-channel peak diffraction efficiencies in the modulation bandwidth are 79.54% and 61.41% respectively. The beat frequency of the first-order diffracted beam and the incident intrinsic beam outputted by the dual-channel configuration of the acousto-optical frequency shifter is 440-640 MHz, Which is twice the single-channel modulated bandwidth output of 220-320 MHz and has a good signal-to-noise ratio.Theoretical analysis shows that the tunable frequency difference obtained by the dual-channel configuration method of the acousto-optic frequency shifter can measure the folding length variation of about 53 mm Law - Perot cavity.