Accurate characterization of mid-infrared ultrashort pulse based on second-harmonic-generation frequency-resolved optical gating

Abstract

We demonstrate a second-harmonic-generation frequency-resolved optical gating (SHG-FROG) apparatus, which can be used to accurately characterize ultrashort mid-infrared laser pulses. An initial guess with constraint both in time and frequency domain is first proposed in principal components generalized projections algorithm (PCGPA), and it outperforms other guesses for the data errors analysis in these SHG-FROG apparatus. A mid-infrared pulse at 3580 nm from our home-built optical parametric amplifier (OPA) system is measured with a good agreement between the retrieved and measured spectrum. Different initial guesses are studied and a further verification is made to compare the measured spectral phase difference with the calculated one by inserting a dispersion plate. The excellent phase agreement verifies the accuracy of the measurement and high reliability of the device.