A Tm:fiber-laser-pumped Ho:YLF non-planar ring laser with fractional image rotation (~77.45 degree per round trip) is presented. The ring laser cavity consists of six flat mirrors with an incident angle on all six mirrors of ∼32.7 degree with a total cavity length of 222 mm. To make the resonator stable, an intracavity lens has been used with different focal lengths of 75, 100 and 300 mm resulting in different TEM₀₀ spot radii. With this configuration, a maximum laser power of 17.3 W was obtained at a wavelength of 2064 nm, corresponding to a slope efficiency of 28% (57%) with respect to incident (absorbed) pump power. The beam quality factor M² was measured to be 6.4, 5.2 and 1.7 with focal length of 75, 100 and 300 mm, respectively. Near and far field images show, that the mode exhibits a strong narrow central spot with some ring structure around it, which can be understood as a superposition of Laguerre-Gaussian modes (l, p) with l = 0. Identical experiments have been carried out with a planar ring configuration without beam rotation resulting in comparable power performance but somewhat better beam quality with M² values of 5.2, 3.5 and 1.4, respectively. The intensity distribution of near and far field in case of a planar cavity is more or less Gaussian.

Date Published: 20 February 2015
PDF: 7 pages
Proc. SPIE 9342, Solid State Lasers XXIV: Technology and Devices, 93420D (20 February 2015); doi: 10.1117/12.2079211

Published in SPIE Proceedings Vol. 9342:
Solid State Lasers XXIV: Technology and Devices
W. Andrew Clarkson; Ramesh K. Shori, Editor(s)