Picosecond transient absorption spectroscopy of the oxide crystals lithium niobate, potassium niobate, potassium titanyl phosphate, cadmium tungstate, lead tungstate, and scandium oxide.

摘要

The fundamental processes of electronic excitation and the subsequent relaxation of electron-hole pairs to lattice defects are becoming well understood in alkali halide crystals; however, these processes are generally not as well known in more complicated materials. In this work, the creation and ensuing relaxation of electron-hole pairs and the lattice defects they produce in oxide crystals, is studied on the subpicosecond and picosecond time scale. A tool useful in studying such processes in alkali halides, ultrafast pump/probe absorption spectroscopy, has been applied in this project on KNbO₃, LiNbO₃, KTiOPO₄, CdWO₄, PbWO₄, and Sc₂O₃.; Radiation induced absorption by 2.9 eV, 0.3 ps, 0.4 mJ/pulse–0.8 mJ/pulse, laser light was studied as a function of pump/probe delay time on the 0 ps to 250 ps time scale for probe wavelengths in the 500 nm–940 nm range in the above oxide crystals. Picosecond absorption spectra and their kinetics were measured and compared with ns electron induced absorption data and defects are suggested to account for the measured data.