19 February 2014 Spectroscopic evaluation of Tm-doped potassium lead halides for 2μm laser cooling applications
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Proceedings Volume 9000, Laser Refrigeration of Solids VII; 90000O (2014) https://doi.org/10.1117/12.2037412
Event: SPIE OPTO, 2014, San Francisco, California, United States
Tm3+ doped solids have shown promising results for laser cooling applications at IR wavelengths of ~2 μm. The extended IR fluorescence of the involved Tm3+ transition (3H63F4), however, requires low-phonon energy hosts reducing the detrimental effect of non-radiative decay through multiphonon relaxation. In this work the temperature dependent absorption and emission properties of Tm doped KPC (hνmax<200 cm-1) and KPB (hνmax<140 cm-1) crystals were evaluated for applications in laser cooling. Under laser pumping both crystals exhibited broad IR fluorescence at room temperature with a mean fluorescence wavelength of 1.82 μm and bandwidth of 0.14 μm (FWHM). Initial experiments on laser-induced heating and cooling were performed using a combined IR imaging and fluorescence thermometry setup. Employing a continuous-wave laser operating at 1.907 μm, Tm: KPC and Tm: KPB crystals revealed a very small heat load resulting in a temperature increase of ~0.3 (±0.1) °C compared to undoped reference samples. Further work on material improvement will be necessary to identify possible non-radiative loss mechanisms and to improve the crystal quality.
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Eric Kumi-Barimah, Eric Kumi-Barimah, Uwe Hömmerich, Uwe Hömmerich, EiEi Brown, EiEi Brown, Sudhir B. Trivedi, Sudhir B. Trivedi, "Spectroscopic evaluation of Tm-doped potassium lead halides for 2μm laser cooling applications", Proc. SPIE 9000, Laser Refrigeration of Solids VII, 90000O (19 February 2014); doi: 10.1117/12.2037412; https://doi.org/10.1117/12.2037412

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