理论研究了影响Sagnac干涉法信噪比提升能力和效率的各项因素。通过控制脉冲的空间分布和衰减片透过率，能够有效提高Sagnac干涉法的效率。Sagnac干涉法提升信噪比的能力与入射脉冲的信噪比有关：入射脉冲信噪比越高，信噪比提升的量级就越大。在SILEX-Ⅰ超短超强脉冲激光装置上建立了实验平台。3 TW压缩器输出的超短超强脉冲光经衰减片进入Sagnac干涉仪，非线性介质为5 cm长的熔石英材料，衰减片透过率为55%。当入射脉冲能量为6.6 mJ时，利用三阶自相关仪测量得到脉冲的信噪比从使用Sagna干涉仪前的10-6提高到了10-7，此时出射脉冲的能量为1.6 mJ，效率为24%。该方法对光束口径没有限制，能够用于大能量条件下短脉冲信噪比的提升。signal-to-noise ratio of short pulse

This paper demonstrates several factors that affect the signal-to-noise ratio(SNR) improvement ability and the energy conversion efficiency of nonlinear Sagnac interferometry. The efficiency can be improved by controlling the spatial distribution of pulse and the transmittance of attenuator. The SNR improvement ability is related to the SNR of input pulse: higher input pulse SNR enhances the SNR improvement. The experimental platform was established on SILEX-Ⅰ laser facility. The ultra-short pulse from 3 TW compressor was attenuated and sent into the Sagnac loop. The nonlinear medium was a 5 cm long fused silica material and the attenuator transmittance was 55%. When the input pulse energy is 6.6 mJ, the pulse SNR is improved from 10-6 to 10-7 by third-order autocorrelator. The energy of the output pulse is 1.6 mJ, with efficiency about 24%. This method has no limit to the beam diameter, and thus can be used for short-pulse SNR enhancement in the large energy conditions.