Thermo-optical parameters measured in ytterbium-doped potassium gadolinium tungstate

SFA, Inc., Naval Research Laboratory, 4555 Overlook Avenue, S.W., Washington, DC 20375, USA.
Applied Optics (Impact Factor: 1.78). 06/2005; 44(15):3093-7. DOI: 10.1364/AO.44.003093
Source: PubMed


Oriented absorption and fluorescence spectra, refractive indices, thermal expansion, and thermal conductivities are reported for the anisotropic laser material ytterbium-doped potassium gadolinium tungstate, Yb3+:KGd(WO4)2. Measurements of negative values for dn/dT lead to the report of several useful athermal orientations for laser propagation.

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    • "Recently, they were recognized to be exceptionally suitable for the use in efficient and powerscalable 2 μm microchip lasers. The key point was the special " athermal " crystal cut [7] providing a positive and nearly spherical thermal lens that is required for mode stabilization in a plano-plano cavity [8]. In particular, continuous-wave (CW) Tm:KYW [9] and Tm:KLuW [10] [11] microchips emitting multi-watt level output at 1.95 μm were reported. "
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    ABSTRACT: We report on passive Q-switching of a Ho:KLu(WO4)2 (Ho:KLuW) microchip laser in-band-pumped by a Tm:KLuW laser at ~1.96 μm. As a saturable absorber, PbSquantum- dot-doped glass was used which exhibits a saturation intensity of ~3 MW/cm2 near 2 μm. Maximum average output power of 84 mW was achieved from the Ho laser at 2.061 μm with a slope efficiency of 42% (with respect to the absorbed pump power). The shortest pulse duration was 30 ns. In the continuous-wave mode, the maximum output power of the Ho laser reached 530 mW at 2.08 μm with a slope efficiency of 88%.
    Full-text · Article · Sep 2015 · IEEE Photonics Technology Letters
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    • "In this way, a thermal lens can result in abrupt drop of the laser output, distortion of the laser beam profile, and thermally-induced birefringence losses [19]. One feasible way to solve this problem is to prepare a so-called athermal laser element with near-zero and/or positive temperature-induced change of the optical path due to near-equal impact of negative dn/dT and positive thermal expansion [16]. For isotropic materials like glasses, this can be realized by variation of the glass composition. "
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    ABSTRACT: The potential of (N_{g}) -cut monoclinic Yb: and Tm:KLu(WO4)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, (Delta ) , 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(WO4)2 crystal and explained on the basis of spectroscopic properties, mode-matching and cavity stability. The thermal lens properties for microchip Tm:KLu(WO4)2 laser are also calculated.
    Full-text · Article · Aug 2014 · IEEE Journal of Quantum Electronics
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    • ". For KGdW, thermal conductivity anisotropy was characterized in [16] and specific heat was determined in [25] [26]. Unfortunately, there is some discrepancy in the literature data about KGdW density [26] [27]. "
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    ABSTRACT: Temperature distribution in the Nd- and Yb- doped YAG and KGdW laser crystals under flashlamp- and diode-pumping was characterized by means of finite element analysis. For KGdW, two laser crystal orientations were considered for light propagation along the Np and Ng optical indicatrix axes, taking into account the anisotropy of thermal conductivity coefficient. The influence of the cooling conditions, pump spot size and dopant concentration on the temperature distribution was analyzed. For flashlamp-pumping conditions, the applicability of the quasi-steady-state model is discussed. The main concerns in the thermal management of KGdW laser host is the relatively low thermal conductivity that results in poor cooling and significant absorption coefficients under diode pumping that result in highly non-uniform volumetric heat deposition. “Athermal” Ng-cut KGdW crystal was found to produce higher temperature gradients that the “standard” Np-cut one, that should results in higher internal stresses and higher probability of thermally-induced cracks.
    Full-text · Article · Oct 2012 · Optics & Laser Technology
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