The conversion of a femtosecond pulse with a central wavelength of 950 nm to the second harmonic

Abstract

The results of theoretical and experimental studies of the second harmonic generation in a Ti:Sapphire femtosecond complex are described. The complex includes a femtosecond pulse generator, a stretcher, a regenerative amplifier, two multipass amplifiers, a compressor, and a second-harmonic generator. The effects of the radiation intensity, beam spatial profile, and the level of the noise component of the first harmonic at a wavelength of 950 nm on the homogeneity of the second harmonic are studied. It is theoretically shown that a good homogeneity of the second harmonic intensity is observed in the absence of the noise component in the beam at the fundamental wavelength. When making the amplitude inhomogeneities in the first harmonic even greater, inhomogeneities in the second harmonic appear. It is experimentally shown that an increase in the noise component in a pumping beam due to the use of a spatial filter allows strong suppression of small-scale inhomogeneities in the second harmonic.