ABSOLUTE NONRADIATIVE ENERGY-CONVERSION-EFFICIENCY SPECTRA IN TI3+-AL2O3 CRYSTALS MEASURED BY NONCONTACT QUADRATURE PHOTOPYROELECTRIC SPECTROSCOPY

Photopyroelectric spectroscopy (PPES) was used in a noncontact experimental configuration to obtain high-resolution absolute spectra of the optical-to-thermal energy-conversion efficiency (nonradiative coefficient), eta(NR)(lambda), of Ti:sapphire laser crystals with widely different figures of merit. Optical-absorption-coefficient beta(lambda) spectra were obtained from the PPES signal in the purely optical transmission mode. These were subsequently used self-consistently in a theoretical model along with PPES-signal quadrature spectra (purely thermal transmission mode) to extract eta(NR)(lambda) spectra. These spectra were found to depend on the optical quality of the bulk and of the polished surfaces of the Ti:sapphire material. Therefore, they can be used for fundamental energy-conversion studies of the excited-state deexcitation manifold, as well as for establishing a practical monitoring criterion of crystal growth and processing quality in Ti3+:Al2O3.