Optical absorption at 1.06 um in highly deuterated potassium dihydrogen phosphate

We have determined the relationship between residual proton (hydrogen) concentration and optical absorption at 1.06 [mu]m 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 [+ or -] 55 parts in [10.sup.6] (ppm) [cm.sup.-1]/% hydrogen for the o- (ordinary-) polarized absorbance at 1.064 [mu]m, and 45 [+ or -] 7 ppm [cm.sup.-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 [+ or -] 228 ppm [cm.sup.-1] and 343 [+ or -] 28 ppm [cm.sup.-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 [+ or -] 0.044. Key words: Deuterated KDP,[KH.sub.2.PO.sub.4], optical absorption.