NONLINEAR SPECTROSCOPY AND PASSIVE Q-SWITCHING OPERATION OF CR4-DOPEDSRGD4(SIO4)(3)O AND CAGD4(SIO4)(3)O CRYSTALS()

The polarized differential absorption spectra of the Cr4+ ion in Cr4+: SrGd4(SiO4)(3)O and Cr4+:CaGd4(SiO4)(3)O crystals were studied under p icosecond excitation. Polarized excited-state absorption (ESA) spectra were derived from the differential absorption spectra by use of the g round-state absorption (GSA) and ESA cross sections obtained from inte nsity-dependent transmission measurements. ESA was assigned to the T-3 (2) --> T-3(1)(F-3) and T-3(2) --> T-3(1)(P-3) transitions of the Cr4 ion. Passive Q switching of a Nd3+:YAlO3 (1.08-mu m) and a ruby (694- nm) laser with the Cr4+:SrGd4(SiO4)(3)O and the Cr4+:CaGd4(SiO4)(3)O c rystals as saturable absorbers was demonstrated. The pulse duration (e nergy) of the Q-switched Nd3+:YAlO3 and the ruby laser were found to b e 55 ns (2.4 mJ) and 90 ns (20 mJ), respectively. (C) 1998 Optical Soc iety of America.