Variation of the refractive index with temperature and the tuning rate for KDP isomorphs

The variation of refractive index with temperature is measured as a function of wavelength, temperature, and polarization for KDP and eight of its isomorphs. These data are used to predict the tuning rate for second-harmonic generation as a function of temperature. The predicted tuning rate compares well with the measured tuning rate. Reasonable agreement is found in most cases, the principal exceptions being those cases in which the data must be extrapolated significantly beyond the range of the measured values.