为实现弱信号对比度的高动态范围测量,基于二阶自相关理论,提出了一种实现纳焦级弱信号对比度高动态范围测量的方法。理论分析了能量(功率)、相位匹配和测量噪声对测量动态范围的影响,发现通过对测量噪声能量的光子计数进行探测、精确设置相位匹配过程中的非共线角,并采用聚焦和滤波方式对测量噪声进行抑制,可有效提升测量的动态范围。在此基础上,建立了一台弱信号高动态范围测量系统,利用神光II高能拍瓦激光种子源,实现了纳焦级弱信号1.0×10 11的高测量动态范围,这一数值与理论分析结果相符;同时,实现了种子源4.3×10 8对比度的准确甄别。研究结果对国内高能拍瓦激光系统对比度的提升具有重要意义。

To achieve the high-dynamic-range measurement for weak signal, a method of realizing contrast measurement in high dynamic range for nJ-level weak signal is proposed based on second-order autocorrelation. The effects of energy (power), phase matching, and measurement noise are theoretically analyzed. The dynamic range can be effectively enhanced via the photon-counting detection of the measurement noise, selection of non-collinear angle in phase-matching and suppression of measurement noise by focusing and filtering. Thus a high-dynamic-range measurement system is established for a weak signal. A high measurable dynamic range of 1.0×10 11 is achieved for the nJ-level weak signal when using the laser source of the Shenguang II high-energy petawatt laser, which is in agreement with the theoretical result. Furthermore, accurate screening is realized for a laser source having a contrast of 4.3×10 8. The obtained results are significant for improving the contrast of the high-energy petawatt laser system.