The conversion of a femtosecond pulse with a central wavelength of 950 nm into the second harmonic
S.V. Alekseev1, N.G. Ivanov1, V.F. Losev1,2, S.Yu. Mironov3
1High Current Electronics Institute of the Siberian Branch of the RAS, 634055, Tomsk, 2/3, Academichesky ave. HCEI SB RAS
2National Research Tomsk Polytechnic University, 30, Lenin Avenue, Tomsk, 634050, Russia
3Institute of Applied Physics of the Russian Academy of Sciences, 46 Ul'yanov Street , 603950, Nizhny Novgorod , Russia
Keywords: фемтосекундный лазерный импульс, генерация второй гармоники, гауссов пучок, нелинейный кристалл, однородность, интенсивность, неоднородность, femtosecond laser pulse, second harmonic generation, Gaussian beam, nonlinear crystal, homogeneity, intensity, inhomogeneity
Abstract
The paper presents the results of theoretical and experimental studies of the second harmonic generation process in the Ti:sapphire femtosecond complex, which includes generator of the femtosecond pulse, stretcher, regenerative amplifier, two multi-pass amplifiers, compressor, and second-harmonic generator. This complex provides 50-fs pulses with energy of 20 mJ and is used as a master oscillator in the THL-100 hybrid laser system, which operates in the visible region at a wavelength of 475 nm. Experiments and calculations for various beam parameters of the fundamental harmonic, such as radiation intensity, spatial profile of the beam, and the level of the noise component, were performed. It is theoretically shown that in the absence of the noise component in the beam of the fundamental wave a good homogeneity of the second harmonic should be observed. When making the amplitude inhomogeneities in the first harmonic even greater inhomogeneities in the second harmonic appeared. It is experimentally shown that the inhomogeneity of the second harmonic beam increases with the beam energy.
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