NONLINEAR ABSORPTION IN GD2SIO5-CR4+ CRYS TAL SUBJECTED TO PICOSECONDEXCITATION

The optical absorption, temperature dependences of the luminescence in tensity and decay time, and the transient absorption spectra of a Gd2S iO5:Cr4+ crystal were determined by the picosecond excitation and prob ing method. An analysis of the results showed that the induced absorpt ion observed in the 600-650 nm range was due to T-3(2)(F-3) --> -->T-3 (1)(P-3) transitions from the excited state. The lifetimes of the T-3( 2)(F-3) and T-3(1)(F-3) levels were estimated to be 15 ns and 12 ps, r espectively. The cross section for absorption from the first excited s tate at the wavelength of 616 nm was (1.1 +/- 0.6) . 10(-18) cm(2) and that for absorption from the ground state at lambda = 540 nm was (2.2 +/- 1.1) 10(-18) cm(2).