Modeling of high-power continuous-wave Tm:YAG side-pumped double-clad waveguide lasers

Abstract

Abstract-A plane-wave model accounting for cross-relaxation, upconversion, ground-state depletion, and gain saturation in continuous-wave laser systems is applied to side-pumped Tm:YAG double-clad planar waveguides. The temperature profile due to high-power pumping, and the delivery and absorption efficiencies of proximity-coupled diode bars, are also calculated. The theoretical performance is found to be a good fit to the experimental results, which show 15-W output at 2 m from 43 W of diode pump power. The output channels for the absorbed power are quantified, and it is shown that upconversion limits the gain and, hence, the size of the output coupling that can be used in such lasers. The same theory is then used to design a very compact waveguide laser capable of delivering 100 W of output power.

Laser operation of a Tm:Y_2O_3 planar waveguide

“…The former process can provide an efficient pumping mechanism with up to two excited ions created for one pump photon, as has been exploited previously in a high-power Tm 3+ :YAG planar waveguide laser [1]. This effect is dependent upon the proximity of the Tm 3+ to neighbouring dopant ions, hence the higher RE ion concentration for yttria per atomic substitution (compared to YAG) should enable sufficient cross-relaxation rates at lower doping levels as reportedly used in early bulk crystal experiments [22].…”

“…Thulium-doped media have several attractive features for generating light in this wavelength band, including a broad emission bandwidth, long-lived metastable states, absorption bands matched to high-power 0.8 µm diode-pump sources, and the potential for high quantum efficiency due to a 2-for-1 crossrelaxation process [1,2]. Waveguide lasers are compact, can be easily integrated with diode pump lasers without additional beam shaping, can have lower thresholds than bulk geometries and have excellent thermal management properties.…”

Er:YGG planar waveguides grown by pulsed laser deposition for LIDAR applications

“…YGG has an acceptable 2.2% lattice-constant mismatch with Y3Al5O12 (YAG), which therefore provides a good substrate on which to grow these doped films. Furthermore, the difference in their respective refractive indices (1.91 for YGG and 1.82 forYAG) means that the resulting waveguide has a large numerical aperture of 0.58, well suited for high-power diode-laser pumping, either through proximity-coupling [4] or focused into the waveguide facets via end-or side-pumping configurations [5]. These features also lend themselves to large-mode-area "double-clad" or pump-guiding designs, which enable fundamental mode selection with the potential for high-power operation.…”

Effect of Tm2O3 doping on microstructure and optical properties of Tm:YAG ceramics

“…In addition, the 3 F 4 level in Tm:YAG is characterized by a long fluorescence lifetime of around 11 ms, which is attractive from the point of view of using this material in Q-switched modulators [21]. Due to showing strong absorption bands in the 785 nm range, thulium can be pumped by AlGaAs laser diodes [22]. Efficient 2 mm laser action was observed also upon in-band pumping at 1617 nm [23].…”