SUMMARY

The variation of the refractive indices with temperature for the KDP isomorphs has been measured as a function of temperature, wavelength, and polarization. For a given wavelength, the variation of refractive indices with temperature is nearly constant when the average temperature varies from 20 to 50℃. Most of the variations of the refractive index are negative, with the magnitude of the variation of the ordinary refractive index being significantly larger than the magnitude of the variation of the extraordinary refractive index. There is also not much change in the variation of the refractive indices with temperature over the wavelength range used in these measurements.

The refractive indices as a function of wavelength were fitted to a one-pole Sellmeier equation. This permitted a simple expression to predict the wavelength at which 90° phase-matched second-harmonic generation occurs. The predictions compare reasonably well with measured values, with the primary exceptions being those cases in which a significant extrapolation from measured values is required. The measurements of the variation of the refractive index with temperature are combined with the one-pole Sellmeier constants to predict the temperature-tuning rate. Again, reasonable agreement between the predictions and measurements are obtained. The exceptions are again primarily restricted to cases in which a large extrapolation from the measured values is required.