Non-critical phase-matched second harmonic generation by beta '-Gd/sub 2/(MoO/sub 4/)/sub 3/ in the near infrared

A two-crystal walkoff-compensated beta -barium metaborate optical parametric oscillator was used to locate the noncritical (90 degrees ) phase-matching (NCPM) wavelengths for type II second-harmonic generation along the crystallographic a- and b-axes of a crystal of beta '-gadolinium molybdate and to measure their spectral and angular acceptances. The relative second-harmonic intensity versus wavelength curves exhibited peaks at 1.403 mu m and 1.410 mu m, respectively, with full widths at half maximum of 7.2 nm and 7.3 nm. The relative second-harmonic intensity versus external angular orientation curves had full widths at half maximum for propagation along the a- and b-axes of 13.6 degrees and 14.1 degrees theta /sub ext/ and 71.5 degrees and approximately 92.3 degrees phi /sub ext/, respectively. These large spectral and angular acceptances are typical of noncritical phase-matching. The discrepancy between calculated and experimental NCPM wavelengths is attributed to the errors inherent in measuring and extrapolating refractive indices.<
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