Nonlinear spectroscopy and passive Q-switching operation of a Co~(2+): LaMgAl_(11)O_(19) crystals

摘要

A pump-probe technique with picosecond resolution was used to record and derive the differential and excited-state absorption (ESA) spectra of a Co~(2+): LaMgAl_(11)O_(19) (LMA) single crystal in the visible and near-infrared spectral regions. Time resolution allowed us to observe ESA bands that can be assigned to a ~4T_2(~4F) -> ~4T_1(~4P) optical transition and to transitions from the thermally populated ~2E(~2G) excited state to doublet levels that arise from the ~2F free-ion level of the tetrahedrally coordinated Co~(2+) ion. Intensity-dependent transmission measurements were also carried out at 1.34 and 1.54 #mu#m. Passive Q switching of Nd~(3+):YAlO_3 (1.34-#mu#m) and of Er~(3+): glass (1.54 #mu#m) lasers by use of the Co~(2+):LMA crystal as a saturable absorber was demonstrated. The pulse durations (energies) of the Q-switched Nd~(3+):YAlO_3 and Er~(3+) :glass lasers were found to be 75 ns (3.7 mJ) and 50 ns (4.5 mJ), respectively.