Thermal lensing and microchip laser performance of N g-cut Tm3+:KY(WO4)2 crystal

Abstract

The thermal lensing effect was characterized in the diode-pumped monoclinic N g -cut Tm:KYW crystal under laser operation conditions at the wavelength of 1.94 µm. The thermal lens was found to be slightly astigmatic; its optical power D being positive for rays lying in all meridional planes. Thermal lens sensitivity factors M = dD/dP abs equal 11.8 m −1 /W and 8.8 m −1 /W (with respect to the absorbed pump power P abs ) for principal meridional planes containing N p and N m axes. Nearly athermal behavior of N g -cut crystal is associated with the mutual compensation of different impacts to the thermal lens optical power that arise from temperature dependence of the refractive index dn/dT and anisotropic thermal expansion. It was utilized to produce passively cooled diode-pumped 0.65 W cw Tm:KYW microchip laser with slope efficiency of 44 % and low thermo-optic aberrations.

Microchip laser operation of Tm,Ho:KLu(WO_4)_2 crystal

“…DTs are typically cut along the growth direction, or b-axis || N p -axis of the optical indicatrix, generating a negative thermal lens that leads to the cavity instability [19]. Only recently it was shown that another cut, along N g -axis, can provide the desired mode stabilization and Tm:DTs microchip lasers were developed [20,21]. Later on, the potential for power scaling to multi-watt levels was confirmed [22].…”

Thermal lensing and laser performance of Tm:LuAG crystal at room temperature

“…In 2011, Yao et al [11] reported the thermal analysis of Tm:YLF crystal and Tm:YAP crystal. In 2012, Gaponenko et al [12] reported the thermal lensing of Tm 3 þ -doped KY(WO 4 ) 2 crystal. The results showed that the thermal effect of Tm 3 þ -doped crystal was quite severe, which would affect the output laser characteristics.…”

Microchip Tm:KYW Laser with 2.5 W of Output Power

“…Many applications require miniature and alignment-free sources, for which microchip or waveguide laser configurations are particularly attractive. Several diode-pumped microchip lasers based on Tm-doped YAG [1], YVO 4 [2], GdVO 4 [3], and KY(WO 4 ) 2 [4] crystals were previously reported. The maximum output power achieved with these lasers was ~ 0.6 W, the maximum slope efficiency relative to the incident pump power being ~30% [3,4].…”

“…Several diode-pumped microchip lasers based on Tm-doped YAG [1], YVO 4 [2], GdVO 4 [3], and KY(WO 4 ) 2 [4] crystals were previously reported. The maximum output power achieved with these lasers was ~ 0.6 W, the maximum slope efficiency relative to the incident pump power being ~30% [3,4]. Recently, we reported on an efficient 1-W TEM 00 diode-pumped Tm:KYW laser with 71% slope efficiency relative to an absorbed pump power and optical-to-optical efficiency of 43%.…”