Department of Mechanical Engineering, National Cheng Kung University, Tainan 70101, Taiwan.
Rev Sci Instrum. 2023 Mar 1;94(3):035008. doi: 10.1063/5.0132179.
Ultrafast lasers concentrate the energy in a short pulse with a duration of several tens to hundreds of femtoseconds. The resulting high peak power induces various nonlinear optical phenomena that find use in many different fields. However, in practical applications, the optical dispersion broadens the laser pulse width and spreads the energy in time, thereby reducing the peak power. Accordingly, the present study develops a piezo bender-based pulse compressor to compensate for this dispersion effect and restore the laser pulse width. The piezo bender has a rapid response time and a large deformation capacity and thus provides a highly effective means of performing dispersion compensation. However, due to hysteresis and creep effects, the piezo bender is unable to maintain a stable shape over time and hence the compensation effect is gradually degraded. To address this problem, this study further proposes a single-shot modified laterally sampled laser interferometer to estimate the parabolic shape of the piezo bender. The curvature variation of the bender is then sent as a feedback signal to a closed-loop controller to restore the bender to the desired shape. It is shown that the steady-state error of the converged group delay dispersion is around 530 fs. Moreover, the ultrashort laser pulse is compressed from 1620 fs in the original condition to 140 fs in the compressed condition, corresponding to a 12-fold improvement.
超快激光器将能量集中在持续几十到几百飞秒的短脉冲中。由此产生的高峰值功率会引发各种非线性光学现象，这些现象在许多不同的领域都有应用。然而，在实际应用中，光学色散会展宽激光脉冲宽度并在时间上扩展能量，从而降低峰值功率。因此，本研究开发了一种基于压电弯曲器的脉冲压缩器，以补偿这种色散效应并恢复激光脉冲宽度。压电弯曲器具有快速的响应时间和较大的变形能力，因此是一种进行色散补偿的高效手段。然而，由于迟滞和蠕变效应，压电弯曲器无法长时间保持稳定的形状，因此补偿效果会逐渐降低。为了解决这个问题，本研究进一步提出了一种单次测量的横向取样激光干涉仪来估计压电弯曲器的抛物线形状。然后，将弯曲器的曲率变化作为反馈信号发送到闭环控制器，以将弯曲器恢复到所需的形状。结果表明，收敛群延迟色散的稳态误差约为 530fs。此外，未压缩时的激光脉冲宽度为 1620fs，压缩后的脉冲宽度为 140fs，压缩比为 12 倍。
