双光梳非线性异步光学采样测距中关键参数的数值分析

Numerical analyses of key parameters of nonlinear asynchronous optical sampling using dual-comb system

双光梳异步光学采样的绝对测距方法具有量程大、测速快和精度高等特点,在几何量精密测量领域具有广泛的应用前景.特别地,结合异步光学采样和非线性强度互相关的倍频信号时域探测方法,可以有效避免测量过程中载波包络偏移频率对测距精度的影响.本文针对双光梳非线性异步光学采样绝对测距系统,对影响其测距精度的理论模型和关键参数进行数值模拟研究.对双光梳异步光学采样的理论模型进行分析后,分别研究了双光梳光源参数(重复频率和重复频率差)、倍频信号精细拟合及脉冲时间抖动对测距精度的影响.数值分析结果表明:选择合理的重复频率和重复频率差有利于提升测距精度,此外适当提高测量速度可以有效降低脉冲时间抖动对测距误差的影响.

Absolute distance measurement based on the asynchronous optical sampling with using a dual-comb system has the characteristics of large range, fast measurement speed, and high accuracy, which has wide application prospects in the field of precision measurement of geometric quantities, such as the space technology, equipment manufacturing, etc. Recently, the invention of the femtosecond frequency comb is a milestone in the field of precision length measurement. Many approaches to the absolute distance measurement have been proposed.Among them, the dual-comb system with asynchronous optical sampling can realize a length measurement with fast speed, high accuracy, and long range. Especially, the temporal method combining the asynchronous optical sampling with nonlinear intensity cross-correlation can effectively avoid influencing of the carrier-envelope offset frequency on the ranging accuracy in the measurement process. The time-of-flight information can be obtained by the time interval between the reference pattern and the measurement pattern. Even so, the selection of the repetition rate and the difference of repetition rates will strongly influence the temporal sampling interval of the measurements. Therefore, the theoretical model and key parameters for the ranging are numerically studied for the non-linear asynchronous optical sampling by using a dual-comb system of absolute distance measurement.After analysis, the effects of source parameters(repetition frequency and repetition frequency difference), fine fitting of second harmonic signal, and timing jitter on ranging accuracy are studied respectively. The numerical analysis results show that the method of choosing a reasonable repetition frequency and repetition frequency difference is beneficial to the improvement of the ranging accuracy. When the sampling interval of the dualcomb system is a constant, the time value between the reference and measurement patterns can be obtained by the interpolation method of fine curve fitting, and it will further improve the ranging accuracy. In addition, the time jitter of the femtosecond pulses is also an important factor that can affect the ranging accuracy. By changing the difference in the repetition rate, the measurement speed can also be improved. After that, the cumulative ranging error caused by time jitter can be reduced. Therefore, the appropriate increasing of measurement speed can effectively reduce the influence of timing jitter on ranging.