Transmission measurements in KTP and isomorphic compounds

The optical biaxial nature of crystals in the potassium titanyl phosphate (KTP) family result in anisotropic transmission that depends on the polarization direction of the transmitted radiation with respect to the fundamental crystal axes. Knowledge of the polarization-dependent crystal transmission is important for all wavelength-conversion applications and in particular is the only limitation on possible combinations of wavelengths when one uses the quasi-phase-matching techniques recently developed for the KTP family materials. In this study, polarized transmission spectra of KTiOPO(4) (KTP), RbTiOPO(4), RbTiOAsO(4) (RTA), and KTiOAsO(4) were measured over the 0.3-6-mum wavelength range with a spectrophotometer and a Fourier-transform infrared spectrometer. Seven crystal samples were studied, including four samples of KTP crystals of different origins. Variations in spectral transmission on the short- and long-wavelength edges, as well as visible-wavelength transmission and OH(-) absorption properties, are presented and discussed. The transmission of one sample of KTP and of RTA was also measured before and after periodic electric field poling.