Characterization of glass and high-power near-infrared cw laser beams using nonlinear optical techniques

Abstract

Absorption coefficients of highly transparent optical materials (glass) have been measured using a z-scan technique. Absorption coefficients as low as 10−5 cm−1 and lower can be measured by scanning a substrate of a transparent optical material in the focal region of a lens. Glass substrates with relatively high absorption coefficients are used for calibration and for verifying the results of measurements. The sensitivity of this technique proves to be high enough to reveal differences between absorption coefficients of different substrates made of the same material (BK7). We have suggested and used a novel procedure, scanning nonlinear lens profiling, for characterization of homogeneity of glass substrates and other transparent optical materials. Optical nonlinearity of glass substrates allows fast and high-precision measurement of the power and power density of high-power near-IR laser beams without large temperature increases and related problems.