Observation of Anti-Stokes Fluorescence Cooling in Thulium-Doped Glass

Abstract

We report the first observation of anti-Stokes fluorescence cooling in a thulium-doped solid with pump excitation at $1.82\ensuremath{\mu}\mathrm{m}<\ensuremath{\lambda}<1.97\ensuremath{\mu}\mathrm{m}$. At a pump wavelength of $1.9\ensuremath{\mu}\mathrm{m}$ and incident average power of $\ensuremath{\sim}3\mathrm{W}$, a ${\mathrm{Tm}}^{3+}$:ZBLANP ( ${\mathrm{ZrF}}_{4}\ensuremath{-}{\mathrm{BaF}}_{2}\ensuremath{-}{\mathrm{LaF}}_{3}\ensuremath{-}{\mathrm{AlF}}_{3}\ensuremath{-}\mathrm{NaF}\ensuremath{-}{\mathrm{PbF}}_{2}$) sample cooled to $\ensuremath{-}1.2\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ from room temperature for a single pass of the pump beam. This corresponds to an absorbed pump power of $\ensuremath{\sim}40\mathrm{mW}$ and a peak temperature change per absorbed power of $\ensuremath{\sim}\ensuremath{-}30\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}/\mathrm{W}$ from room temperature.