Dispersion equations for nonlinear optical crystals: KDP, AgGaSe(2), and AgGaS(2).

A method that uses improved mathematical forms and data-processing techniques has been developed for generating index dispersion equations for nonlinear optical crystals. The data may be diverse, including measured indices of refraction, type I, II, or III critically phase-matched angles, noncritically phase-matched wavelengths, non-phase-matched coherence lengths, isoindex wavelengths, and optical retrace wavelengths and angles. The method automatically estimates and compensates for heretofore unknown crystal orientation errors, attributed principally to manufacturing inaccuracies. In the examples given here, 13-parameter fits to refractive indices n(o) and n(e) are required to reconcile literature data(0.49-12 μm) for AgGaS(2), whereas ten-parameter fits are required for KDP (0.18-1.5 μm) and AgGaSe(2) (0.8-15.5 μm). These examples demonstrate improvements in precision over a wider wavelength range than those for previously calculated refractive indices and critically phase-matched angles, as well as non-critically phase-matched and isoindex wavelengths.