INTENSITY PUMP EFFECTS IN THE KINETICS OF I-4(11 2) LEVEL IN ERAG/

A detailed analysis of the non-exponential behaviour of the kinetics o f the initial laser level for three-micrometer generation I-4(11/2), i n ErAG (Erbium Aluminium Garnet) crystals (laser transition I-4(11/2) --> I-4(13/2)), excited in the H-2(11/2) level with short laser pulses of variable intensity, is performed. The observed non-exponentiality of the I-4(11/2) decay and its dependence on the energy of the excitin g pulse cannot be satisfactorily described with a rate equation modell ing which includes only two-ion energy transfer processes among Er3+ i ons as up-conversion from the terminal laser level (I-4(13/2)), up-con version from the initial one, and cross-relaxation from I-4(9/2) and S -4(3/2) (thermalised, at room temperature, with H-2(11/2)). Our analys is has shown that the inclusion of three-ion up-conversion processes f rom both initial and terminal three-micrometer laser levels leads to a n excellent agreement between experimental and theoretical non-exponen tiality of the I-4(11/2) decay for various pumping intensities and all ows the estimation of the three-ion up-conversion rates. (C) 1998 Else vier Science B.V. All rights reserved.