Improved fluorescence thermometry of Yb:YLF

We report on a novel technique using a robust-set of calibrated fluorescence spectra of Yb:YLF to match spectral features for changes in emission due the sample’s temperature and the location of the pump excitation depth relative to the fluorescence collection system. This is an improvement to the existing Differential Luminescence Thermometry method, where uncertainties in the measured temperature arise from spectral changes due to collection or pump beam location and angle. We further discuss our continued efforts to predict and validate the minimum achievable temperature, by rigorously including effects of absorption saturation in the optical refrigeration experiments and analysis.