Thermal-Lens-Driven Effects in $N_{\mathrm {g}}$ -Cut Yb-and Tm-Doped Monoclinic KLu(WO₄)₂ Crystals

Abstract

The potential of N g -cut monoclinic Yb: and Tm:KLu(WO 4 ) 2 laser crystals is analyzed from the point of view of thermal lensing, including "athermal" behavior, unique laser mode stabilization by polarization-switching and potential for microchip operation. To this aim, we characterize dispersion and direction-dependence of the "generalized" thermo-optic coefficients, Δ, for the light polarizations, E || N m and N p , and calculate sensitivity factors of the thermal lens for wide range of experimental conditions including crystal temperature, laser wavelength, pump spot radius, as well as their relation to probe beam measurements. The polarization-switching between N m and N p oscillating states is realized for a Tm:KLu(WO 4 ) 2 crystal and explained on the basis of spectroscopic properties, modematching and cavity stability. The thermal lens properties for microchip Tm:KLu(WO 4 ) 2 laser are also calculated.

Dual-wavelength operation of a diode-pumped Yb:KGW laser

“…A dual-wavelength oscillation at 1028.7 nm (E//Nm) and 1037.5 nm (E//Np) with 4.6 W of output power using 5% output coupling could be generated and the wavelength separation slightly depended on the output coupling level. Similar thermal-lens driven polarization switching in dualwavelength operation was also observed in a Tm:KLWO 4 2 laser [8].…”

Prospects of monoclinic Yb:KLu(WO_4)_2 crystal for multi-watt microchip lasers

“…A similar effect was detected in [24] and explained in [25] for an acut Yb:CALGO crystal. For Yb:KLuW, it was predicted theoretically in [26]. In all cases, polarization-switching was attributed to the anisotropic thermal lens introducing different losses for the two orthogonal polarizations.…”

“…We calculated the optical power of the thermal lens for Yb:KLuW and E || N p , and it is shown as dashed line in Fig. 3(a) (see details in [26]). The thermal lens for E || N p is always positive, i.e.…”

Watt-level ultrafast laser inscribed thulium waveguide lasers

“…As for the thermal properties, the thermal conductivity of MDT is moderate (κ~3.5 Wm À1 K À1 for KLu(WO 4 ) 2 ) [50]. The thermo-optical effects in MDTs can be greatly suppressed owing to their "athermal" behavior [51,52], i.e., a mutual compensation of contributions to the variation of the optical path length arising from the negative thermo-optic coefficients (dn/dT < 0) [53] and positive thermal expansion [54]. These properties lead to a weak, positive and nearly spherical thermal lens for certain crystal orientations with a reduced effect on the laser mode [55][56][57][58][59].…”