Abstract

Using vanadate as host for the thulium sensitised 2-μm holmium transition offers several advantages over YAG. As shown in Fig. 1, the vanadate absorption is considerably stronger, broader, and closer to 809 rm, the standard wavelength for high power diode lasers, than YAG. The S polarised absorption spectrum has a maximum at 979 nm of α = 19.1 cm^-1 and a FWHM of 7 nm. Pump wavelength dependence is therefore reduced and crystals with lengths under 1 mm can be used. High numerical aperture pump beams can be used as the energy is deposited before the beam can diverge out of the resonator mode, severely reducing the collimation requirements of the diode coupling optics.

© 1994 IEEE