Comparison of different methods for the spatially resolved measurement of losses in optical crystals

This paper presents and compares two methods for spatially resolved 2D-measurement of optical losses in laseractive and nonlinear optical crystals. In the first method, the losses are determined from the decrease of the finesse of an optical resonator when the crystal is inserted. The second method uses the dependency of the power enhancement inside the cavity and the fraction of the laser power reflected from the incoupling cavity mirror on the intracavity losses. These methods provide a spatial resolution as high as 120 μm. The absolute accuracy is up to 0.001%. PACS 81.70.Fy; 78.20.Ci