研制了一套基于多光子脉冲内干涉相位扫描方法的可以同时对飞秒激光脉冲进行相位测量和补偿的实验系统装置.实验中,通过自主研发的LabVIEW程序控制液晶空间光调制器和光纤光谱仪,对待测飞秒激光脉冲施加相位扫描,并同时记录受到调制的飞秒激光脉冲的倍频光谱,得到了多光子脉冲内干涉相位扫描(MIIPS)轨迹图.通过MIIPS轨迹图的三次测量和迭代运算,还原出了经过预先啁啾调制的中心波长约为810 nm、重复频率为1 kHz的飞秒激光脉冲的光谱相位,测量精度在0.1 rad以内.根据测量结果,利用液晶空间光调制器对该飞秒激光脉冲进行相位补偿,得到了近似傅里叶变换极限的飞秒激光脉冲.这一装置将在多光子显微成像、脉冲整形、飞秒激光光谱学等众多领域发挥重要作用.
In this paper, we develop a system that can be used to measure and compensate spectral phase of femtosecond laser pulses based on the multi-photon intra-pulse interference phase scan (MIIPS). In the system, a liquid crystal spatial light modulator (LC-SLM) is used to impose phase scan on the femtosecond laser pulse, while a spectrometer is used to record the MIIPS trace. Both the LC-SLM and the spectrometer are driven by home-developed LabVIEW programs. By analyzing the MIIPS trace, we obtain the spectral phase of the pre-chirped femtosecond laser pulse with only 3-times iteration. The femtosecond laser pulse is centered at 810 nm and has a repetition of 1 kHz. The accuracy of our measurement is less than ±0.1 rad. The measured phases are compensated by the LC-SLM, then we obtain a femtosecond laser pulse which is almost in the transform limit state. The device will be useful in many fields, for example, multi-photon microscopy, pulse shaping, and femtosecond laser spectroscopy etc.