DEFECTS IN BETA-BAB2O4 (BBO) CRYSTALS OBSERVED BY LASER-SCANNING TOMOGRAPHY

Beta barium borate (BBO: beta-BaB2O4) crystals are very useful for opt ical parametric oscillation and harmonics generation of not only the s econd but also the third, fourth and fifth harmonics. Since defects ob served by light will play important roles, especially when the wavelen gth of the light is in the same range as that of the second harmonics or of a laser for excitation, defects in the crystals were optically o bserved by laser scanning tomography. Dislocations observed by laser s canning are estimated to occur in the density of 10(3)-10(4) cm-2, hav e very complicated shapes and are decorated by impurities or excess at oms caused by possible deviation from stoichiometry. It was confirmed here that density of the defects detected optically provides a good fi gure of merit for nonlinear optical applications of BBO prisms, since the optical detection of defects informs harmful ones in a nondestruct ive and noncontacting way.