The recent advances in the development of Holmium monoclinic double tungstate thin-disk lasers are reviewed. The thin-disk is based on a 250-μm-thick 3 at. % Ho:KY(WO4)2 active layer grown on a (010)-oriented KY(WO4)2 substrate. When pumped by a Tm-fiber laser at 1960 nm with a single-bounce pump geometry, the continuous-wave Ho:KY(WO4)2 thin-disk laser generates an output power of 1.01 W at 2057 nm corresponding to a slope efficiency η of 60% and a laser threshold of only 0.15 W. The thin-disk laser is passively Q-switched with a GaSb-based quantum-well semiconductor saturable absorber mirror. In this regime, it generates an average output power of 0.551 W at ~2056 nm with η = 44%. The best pulse characteristics are 4.1 μJ / 201 ns at a repetition rate of 135 kHz. The laser performance, beam quality and thermo-optic aberrations of such lasers are strongly affected by the Ho3+ doping concentration. For the 3 at.% Ho3+-doped thin-disk, the thermal lens is negative (the sensitivity factors for the two principal meridional planes are -1.7 and -0.6 m-1/W) and astigmatic. The Ho:KY(WO4)2 epitaxial structures are promising as active elements in mode-locked thin-disk lasers at ~2060 nm.
We demonstrate the first thin disk epitaxial Tm-laser based on the monoclinic KLu(WO4)2 with 15 at. % doping. The
doped epitaxial layer serving as an active medium is only 80 μm thick. The large absorption enables efficient pumping
with only a single double pass of the pump radiation from the diode-laser. For output coupling between 0.4% and 2.8 %,
the slope efficiency in the continuous-wave regime is in the 7-11% range and the laser threshold is 1.5...2.5 W of
absorbed pump power. The laser emission spectra are centered at ~1850, 1915 and 1940 nm for output couples of 2.8%,
1.6% and 0.4% transmission, respectively. In all cases the emission spectra are "structured", consisting of a number
(typically 5...10) of narrow emission lines spread irregularly over 15...30 nm.
We demonstrate high-efficient CW thin disk 15%Tm:KYW laser pumped by a 20W CW laser diode bar at 803nm.
Three 15%Tm:KYW b-cut disks of 200, 250 and 300&mgr;m thickness are tested, with the maximal laser output being of
4.9W at ~1.9&mgr;m. Slope and optical-to-optical conversion efficiencies are reported as well.
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