Negative thermo-optical coefficients and athermal directions in monoclinic KGd(WO4)2 and KY(WO4)2 laser host crystals in the visible region

Thermal lensing in high-power diode-pumped Yb:KGW laser

“…%-doped active elements pumped by two high brightness, polarization preserving laser diode pump modules of 50 W maximum optical output power at 980 nm wavelength, produced by Light Conversion Ltd., and ensuring pump intensity on the crystal up to 70 kW/cm 2 . Crystal orientation and orientation of thermal expansion axes [12][13][14] in relation to laser beam propagation is shown in Fig. 2.…”

“…• clockwise from the optical axis N m [12,13]. This athermal direction was investigated by Hellstrom et al [5].…”

“…Unfortunately, data regarding the thermally induced astigmatism have not been reported there. However, based on recent measurements of thermo-optic coefficients and thermal expansion using a homogeneous heating, Biswal et al [12,13] proposed possible athermal propagation directions, where the thermooptic and thermal expansion effects approximately cancel each other. One of the proposed directions for the light polarized along the N p axis is in the m-g plane, 15…”

All-space existence and dispersion of athermal directions in monoclinic KY(WO4)2

“…In the present paper, we perform our original fitting of Sellmeier formulas based on our own measurements of the refractive indices [24], as well as data presented in [32]. It was motivated by the fact that previously reported formulas cannot adequately describe the position of optical axes in KY(WO 4 ) 2 .…”

“…From the other hand, monoclinic DTs are optically biaxial, so the solution of this problem is rather complicated. Thus, two routes were proposed in the literature, namely experimental studies of thermal lensing [20][21][22][23] on the material parameters [12,15,24]. First route is limited, as results obtained can be applied only for specific experimental geometry.…”