The polarized differential absorption spectra of the Cr4+ ion in Cr4+:SrGd4(SiO4)3O and Cr4+:CaGd4(SiO4)3O crystals were studied under picosecond excitation. Polarized excited-state absorption (ESA) spectra were derived from the differential absorption spectra by use of the ground-state absorption (GSA) and ESA cross sections obtained from intensity-dependent transmission measurements. ESA was assigned to the 3T2→ 3T1(3F) and 3T2→3T1(3P) transitions of the Cr4+ ion. Passive Q switching of a Nd3+:YAlO3 (1.08-μm) and a ruby (694-nm) laser with the Cr4+:SrGd4(SiO4)3O and the Cr4+:CaGd4(SiO4)3O crystals as saturable absorbers was demonstrated. The pulse duration (energy) of the Q-switched Nd3+:YAlO3 and the ruby laser were found to be 55 ns (2.4 mJ) and 90 ns (20 mJ), respectively.
© 1998 Optical Society of America
K. V. Yumashev, N. N. Posnov, I. A. Denisov, V. P. Mikhailov, and R. Moncorge, "Nonlinear spectroscopy and passive Q-switching operation of Cr4+-doped SrGd4(SiO4)3O and CaGd4(SiO4)3O crystals," J. Opt. Soc. Am. B 15, 1707-1713 (1998)