Kinetics of nonlinear absorption in a reduced strontium titanate single crystal under picosecond excitation conditions

An investigation was made of the nonlinear absorption spectra of a chemically reduced SrTiO₃ single crystal excited by picosecond light pulses. Differences were found between the dynamics of the induced absorption and transparency when excitation corresponded to different absorption bands which appeared as a result of reducing annealing and had maxima at 1.7 and 2.4 eV. The experimental results were used to propose an energy-level scheme of a reduced SrTiO₃ single crystal.