Lasing performance of a 3-σm (Ho,Yb):Y3Al5O12 laser

Lasing in (Ho, Yb): YAG has been reported previously, but little is known about the performance of this potentially useful solid-state laser. The initial lasing tests were performed in a silver-coated single-elliptical-pump cavity; 70 mm of the rod was pumped by a 75-mm xenon-filled flashlamp. A flat output coupler was used with 90% R at 2.94 μm. The pump pulse was rectangular with a duration of 300-μs FWHM. With 245-J input to the lamp, lasing began --15 μs before the pump pulse leveled off, and a total of 45 mJ of output laser energy was detected. Relaxation spikes were observed for --50 μs with the first --25 μs at a wavelength of 2.942 +- 0.002 μm and the balance of the pulse at 3.013 +- 0.002 μm. The output waveform was a train of relaxation oscillation spikes lasting --30 μs. When a flat 99% R output coupler was used the lasing threshold 5.5 J at a prf of 15 Hz. This average input power produced sufficient thermal lensing to assure a stable optical resonator. Operation at a prf of 39 Hz was also demonstrated with a 10-J threshold