DIODE PUMPING AND LASER PROPERTIES OF YB-HO-YAG

The rare-earth ion Yb3+ is an efficient sensitizer for Ho3+ crystal la sers. It has a broad absorption band lying in the emission range of co mmercially available InGaAs diode lasers and an efficient energy trans fer to Ho3+. We have investigated four Yb3+:Ho3+:YAG laser crystals wi th 16.1 and 30.3 at.% Yb3+, both with 2 at.% Ho3+ and two different cr ystal thicknesses. The pump absorption coefficient alpha is about 15.1 cm(-1) for 16.1 at.% Yb3+ in YAG at lambda = 936 nm. Due to the stron g absorption, relatively thin crystals with a thickness of 0.5 and 1 m m were used in active mirror configuration. Room temperature cw laser emission has been achieved in all these crystals. The laser thresholds have been measured as a function of the crystal temperature between 0 and 60 degrees C. Thresholds and slope efficiencies of the different crystals are compared. Under diode laser pumping room temperature quas i cw emission up to 370 mW has been achieved in a 15-mm-long resonator for the first time. (C) 1998 Elsevier Science B.V. All rights reserve d.