Frequency doubling of ultrashort pulses in a nonlinear photonic strontium tetraborate crystal

The second harmonic generation (SHG) of the femtosecond titanium-sapphire laser radiation was experimentally studied in the mode of nonlinear diffraction in the nonlinear photonic strontium tetraborate crystal. The spectrum of reciprocal lattice vectors of domain structures includes components responsible for the efficient frequency-tunable SHG in the spectral range of 355–510 nm. The maximum SHG efficiency was 1.9%. The SHG spectrum narrowing does not exceed 10–20%. The measured spectral dependence of the nonlinear diffraction angle is in good agreement with calculation.