Chang Jui-Chi, Chang Shu-Yu, Wu Yu-Cheng, Chang Chia-Yuan
Department of Mechanical Engineering, National Cheng Kung University, Tainan 70101, Taiwan.
Rev Sci Instrum. 2021 Nov 1;92(11):113702. doi: 10.1063/5.0060564.
In ultrashort pulse laser applications, optical dispersion seriously affects the energy concentration in the laser pulse duration and lowers the peak power. Accordingly, this study proposes a rapid dispersion estimation mechanism to facilitate the compensation of optical dispersion using a closed-loop control system. In the proposed approach, the optical dispersion information of the laser pulse is estimated directly from a frequency-resolved optical gating trace without the need for an iterative pulse-retrieval algorithm. In particular, the group delay dispersion (GDD) is determined from frequency and delay marginals, which are related to the laser spectrum and intensity autocorrelation, respectively, using a simple lookup table approach. The accuracy of the estimated GDD results is confirmed via a comparison with the spectral phase distribution of the electric field reconstructed using the principal component generalized projections algorithm. It is shown that the computation time of the proposed direct estimation method is around 13 times faster than that of the traditional iterative algorithm. It thus provides a feasible approach for enabling the real-time compensation of ultrafast laser pulse compression. Moreover, in a multiphoton-excited fluorescence imaging application, the proposed pulse compression mechanism yields an effective improvement in the intensity and contrast of the reconstructed image due to the increased nonlinear optical excitation efficiency of the optimized laser pulses.
在超短脉冲激光应用中，光学色散严重影响激光脉冲持续时间内的能量集中度，并降低峰值功率。因此，本研究提出一种快速色散估计机制，以利用闭环控制系统促进光学色散补偿。在所提出的方法中，无需迭代脉冲检索算法，直接从频率分辨光学门控迹线估计激光脉冲的光学色散信息。特别是，利用简单的查找表方法，分别从与激光光谱和强度自相关相关的频率和延迟边缘确定群延迟色散（GDD）。通过与使用主成分广义投影算法重建的电场光谱相位分布进行比较，证实了估计的GDD结果的准确性。结果表明，所提出的直接估计方法的计算时间比传统迭代算法快约13倍。因此，它为实现超快激光脉冲压缩的实时补偿提供了一种可行的方法。此外，在多光子激发荧光成像应用中，由于优化激光脉冲的非线性光学激发效率提高，所提出的脉冲压缩机制有效提高了重建图像的强度和对比度。
