Real-time temporal characterization of femtosecond laser pulses by using the spectral phase intereferometry for direct electric field reconstruction (SPIDER) method

Abstract

This thesis consists of two parts: the first part concentrates on the principle of femtosecond laser pulses using Titanium Sapphire as a gain medium. This part considers fundamentals of ultrashort laser pulses, generation, amplification and characterizations of femtosecond laser pulses. The second part deals with the real-time temporal characterization of femtosecond laser pulses by using the Spectral Phase Interferometry for Direct Electric Field Reconstruction (SPIDER) method. It is an accurate and rapid method for characterization of femtosecond laser pulses. This technique, which is based on spectral interferometry, spectral shearing and sum frequency generation (SFG), utilizes a direct inversion routine to reconstruct the spectral phase. The electric field in the time domain is obtained directly from the combination of spectrum and spectral phase. This part of the thesis describes simulation, optimization and implementation of a real time SPIDER: a version of SPIDER that has been optimized and constructed for real time measurements. Comparing to the original setup, this experimental setup has some advantages that can be listed as follows: the use of an etalon glass to avoid instability from the use of Michelson`s interferometer and unwanted group delay dispersion (GDD) raising from its beam splitter, careful selection of the thickness of an etalon for optimum pulse separation, optimum selection of SFG crystal thickness for given characteristics of laser pulses in order to get the most efficient SFG, the use of a periscope to rotate the polarization of input pulses instead of using broadband half wave plate (due to the imperfection of broadband wave plates) and finally that is the optimization of data acquisition and data analysis to perform SPIDER acquisition in real time. The result is then compared to the result acquired by the frequency-resolved optical gating method. The consistency between two results shows that SPIDER is truly an accurate technique...