Femtosecond-laser experiment for Master Ⅱ students: Generation, measurement and control of femtoseconds pulses

摘要

In the framework of the experiment platform LEnsE (Laboratoire d'Enseignement Experimental) of the Institut d'Optique Graduate School in Palaiseau, we present a new lab work dedicated to Master-Ⅱ-level students. This lab work is integrated in the formation in the field of ultrashort-pulse lasers and its objective is to train students to this specific technology. The varied topics include generation, measurement and basic control of ultrashort pulses. Key concepts are studied, such as the time-frequency duality, nonlinear effects, the group velocity dispersion (GVD) and more generally managing spectral and temporal phase. The lab work is based on a totally accessible Ti:sapphire laser (Mira 800 from Coherent). It is used to understand crucial concepts in the generation process such as GVD and self-phase-modulation in the solitonic regime and Kerr lens mode-locking. Because the pulse measurement is a crucial issue to address in ultrafast optics, the lab work also studies different apparatus commonly used to fully characterize fs pulse train: photodiode, spectrometer, and more specifically second-order autocorrelator. The autocorrelation concept is detailed using a homemade accessible apparatus. For a simple manipulation of femtosecond pulses, we propose to realize a spectral-phase control with high-dispersive glass to temporally stretch the pulses. GTI mirrors then re-compress them. The three pillars generation-measurement-control will be described with a practical approach at the conference.