Single-gate boxcar-integrator time-domain photothermal radiometry (PTR) is proposed as a noncontact remote technique with a high signal-to-noise ratio that can evaluate the optical quality of the surface in a solid-state laser-gain medium such as Ti:sapphire. It was found that immediately after the boxcar-averaged laser-pulse cutoff, the PTR signal is dominated by the laser metastable-level transition lifetime. A PTR theoretical model was formulated to account for this effect and to deconvolute its contribution to the signal from surface absorption of the laser radiation. With the theoretical model, the surface contribution to experimental boxcar PTR signals was deconvoluted and the surface quality was quantified in terms of the surface nonradiative energy generation rate, as the percentage of the input optical power that is converted to heat.
© 1998 Optical Society of America
J. Vanniasinkam, A. Mandelis, M. Munidasa, and M. Kokta, "Deconvolution of surface and direct metastable- state blackbody emission in Ti:sapphire laser materials using boxcar time-domain photothermal radiometry," J. Opt. Soc. Am. B 15, 1647-1655 (1998)