Two-photon-excited fluorescence in KTiOPO4 polycrystals

The spectra of two-photon-excited fluorescence in KTiOPO₄ were obtained at room temperature. A coppervapor laser was used as a source of excitation light and provided two emission lines (λ=510.6 and 578.2 nm). The laser operated at a high pulse-repetition rate (～ 10⁴ Hz) and featured a peak power of about 10⁴ W, average power of 1 W, and pulse duration of 20 ns. The fluorescence spectra of crystalline KTiOPO₄ are compared with the resonance fluorescence spectra of KTiOPO₄ at 4.2 K. The measured decay time of fluorescence was found to be less than 16 ns. The efficiency of conversion of the laser radiation to fluorescence was about 10^?10 under saturation conditions.