LASER-RELATED PROPERTIES OF CHROMIUM AND NEODYMIUM-DOPED GADOLINIUM SCANDIUM ALUMINUM GARNET (CR-ND-GSAG)

The spectroscopic, lasing, and thermal properties of chromium- and neo dymium-doped gadolinium scandium aluminum garnet (Cr:Nd:GSAG) are repo rted. The Judd-Ofelt parameters, radiative lifetime, and branching rat ios were determined, and an effective emission cross-section value of 0.92 x 10(-19) cm(2) was derived at 1.06 mu m from our spectroscopic m easurements. The temporal behavior of the Cr(3+-)fluorescence intensit y agreed with the Inokuti-Hirayama model for the chromium-neodymium en ergy-transfer mechanism, which invokes a static dipole-dipole interact ion and no migrational energy transfer. Under identical flash-lamp-pum ping conditions the measured pumping efficiency of Cr:Nd:GSAG for thre shold lasing is nearly equal to the pumping efficiency of codoped gado linium scandium gallium garnet (Cr:Nd:GSGG). From the threshold-lasing data, an effective emission cross section of 0.7 x 10(-19) cm(2) for Cr:Nd:GSAG was independently determined, as well as a value of 1.3 x 1 0(-19) cm(2) for Cr:Nd:GSGG. The normalized heating parameter X, defin ed as the heat deposited per unit stored energy, experimentally ranges from 2.1 to 2.7, depending on the effective emission cross-section va lue. Our calculated value of X is 1.9 +/- 0.3. Based on our heating-ef ficiency measurements, calculated Cr:Nd:GSAG thermal lensing values ar e similar to 2.1-2.6 D/kW, which indicates a thermally induced focal l ength that is weaker than that of Nd:YAG by approximately a factor of 2 at the same output power. Finally, the benefits and trade-offs of la ser-diode pumping are discussed.