Measurement of solid-state optical refrigeration by two-band differential luminescence thermometry

Abstract

We present a non-contact optical technique for the measurement of laser-induced temperature changes in solids. Two-band differential luminescence thermometry (TBDLT) achieves a sensitivity of ϳ7 mK and enables a precise measurement of the net quantum efficiency of optical refrigerator materials. The TBDLT detects internal temperature changes by decoupling surface and bulk heating effects via time-resolved luminescence spectroscopy. Several Yb 3+-doped fluorozirconate (ZrF 4-BaF 2-LaF 3-AlF 3-NaF-InF 3 , ZBLANI) glasses fabricated from precursors of varying purity and by different processes are analyzed in detail. A net quantum efficiency of ͑97.39± 0.01͒% at 238 K (at a pump wavelength of 1020.5 nm) is found for a ZBLANI:1% Yb 3+ lasercooling sample produced from metal fluoride precursors that were purified by chelate-assisted solvent extraction and dried in hydrofluoric gas. In comparison, a ZBLANI:1% Yb 3+ sample produced from commercialgrade metal fluoride precursors showed pronounced laser-induced heating that is indicative of a substantially higher impurity concentration. The TBDLT enables rapid and sensitive benchmarking of laser-cooling materials and provides critical feedback to the development and optimization of high-performance optical cryocooler materials.

Local laser cooling of Yb:YLF to 110 K

“…Due to the large electronic bandwidth and high common-mode-rejection of these detectors, a fast and shot-noise-limited performance can be obtained relatively easily. Fluorescence spectrum can be sampled for example by means of a monochromator (MC) [24], color filters [25], or any other spectrally selective components. Color filters for example are more suitable for resolving a temperature-induced spectral linewidth change of a fixed transition frequency (e.g.…”

Cryogenic optical refrigeration

“…The first demonstration of net laser cooling of a solid was accomplished in 1995 by Epstein and co-workers at Los Alamos National Laboratory using a highly pure ytterbium-doped fluorozirconate glass Yb 3+ :ZBLANP [9]. Since then, optical refrigeration has been confirmed in a variety of glasses and crystals doped with Yb 3+ (ZBLANP [9,[22][23][24][25], ZBLAN [26][27][28][29][30][31], ZBLANI [32], CNBZn [33,34], BIG [28,35,36], KGd(WO 4 ) 2 [37], KY(WO 4 ) 2 [37], YAG [37,38], Y 2 SiO 5 [38], KPb 2 Cl 5 [33,39], BaY 2 F 8 [40,41], YLF [42][43][44], ABCYS [45]), Tm 3+ (ZBLAN [46,47], BYF [48]), and Er 3+ (CNBZn [49], KPb 2 Cl 5 [49,50]). The inverse dependence of the cooling efficiency η c on the pump energy [Eq.…”

Preparation and Characterization of High‐Purity Metal Fluorides for Photonic Applications

“…The phase purity of each metal fluoride was verified by a commercial X‐ray diffractometer (XRD, Rigaku, The Woodlands, TX). Two‐band differential luminescence thermometry (TBDLT) was used to measure local laser‐induced cooling or heating in ZBLANI:Yb 3+ samples.…”