Tm:Ho:GdVO₄ laser at 2 μm using laser-diode double-end pumping

Continuous wave (CW) and quasi continuous wave (QCW) Tm:Ho:GdVO₄ solid laser at 2.049 μm using laser-diode (LD) double-end pumping is reported. The fibre-coupled LD emits a maximum power of 27.7 W at 805 nm with a fiber core diameter of 400 μm and a fiber numerical aperture of 0.22. The LD output is divided into two beams with the same power and double-end pumped the laser crystal. The crystal is co-doped with 5% Tm and 0.5% Ho in dimensions 4 mm × 4 mm × 7 mm. The spectroscopy and energy loss of the Tm:Ho system is analyzed. The crystal is cooled with liquid N₂ for improving the output power and extracted efficiency. The output power of 9.4-10.1 W is obtained at 5, 10, 20-kHz Q-switched and CW modes, corresponding to the optical-to-optical efficiency of 34%-36%. Also, the maximal energy per pulse of 1.9 mJ and the maximal peak power of 0.13 MW are obtained. Additionally, both the alteration of the pump power and that of the repetition rate influence the pulse width.