Efficient second harmonic conversion of broad-band high-peak-power Nd:glass laser radiation using large-aperture KDP crystals in quadrature

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Abstract
The authors have investigated the second-harmonic conversion efficiency of broadband Nd:glass laser light ( Delta nu /c<30 cm/sup -1/ FWHM). Using two KDP crystals in a quadrature arrangement, they obtain energy conversion efficiencies of approximately=55% with an initial bandwidth for the fundamental of Delta nu /c approximately=17 cm/sup -1/ FWHM. For these conditions, a modest increase ( approximately=70%) was observed in the harmonic bandwidth (FWHM) relative to the fundamental. The usual theory of three-wave mixing in dispersive birefringent nonlinear crystals is extended to describe the broadband harmonic conversion process; the generalized theory includes the statistical properties of the light and phase mismatch effects on the spectral components in the complex field amplitudes. Good agreement is found between the code calculations and the measurements.