Optical absorption at 1.06 microm in highly deuterated potassium dihydrogen phosphate.

We have determined the relationship between residual proton (hydrogen) concentration and optical absorption at 1.06 microm in highly deuterated potassium dihydrogen phosphate (KDP). The proton concentration was determined by nuclear magnetic resonance (NMR) spectroscopy and the absorbance was measured by calorimetry. We obtained a hydrogen concentration dependence of 396 +/- 55 parts in 10(6) (ppm) cm(-1)/% hydrogen for the o- (ordinary-) polarized absorbance at 1.064 microm, and 45 +/- 7 ppm cm(-1)/% hydrogen for the e- (extraordinary) polarization. In addition, the KDP crystals we tested have residual (hydrogen-independent) o- and e-polarized absorbances of 958 +/- 228 ppm cm(-1) and 343 +/- 28 ppm cm(-1), respectively, whose origin is unknown. We also found that the crystal deuterium-hydrogen (D-H) ratio can be related to the D-H ratio of the growth solution by a simple ideal mixture model with a segregation coefficient of 0.684 +/- 0.044.