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Synthesis and evaluation of rare-earth doped glasses and crystals for optical refrigeration

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/10315

Synthesis and evaluation of rare-earth doped glasses and crystals for optical refrigeration

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Title: Synthesis and evaluation of rare-earth doped glasses and crystals for optical refrigeration
Author: Patterson, Wendy Marie
Advisor(s): Sheik-Bahae, Mansoor
Hehlen, Markus
Committee Member(s): Krishna, Sanjay
Thomas, James
Department: University of New Mexico. Dept. of Physics & Astronomy
Subject: optical refrigeration
laser cooling of solids
rare-earth
luminescence thermometry
fluorozirconate glasses
LC Subject(s): Laser cooling--Materials.
Laser cooling--Materials--Testing.
Rare earth fluorides.
Metallic glasses.
Fluoride glasses.
Degree Level: Doctoral
Abstract: This research focused on developing and characterizing rare-earth doped, solid-state materials for laser cooling. In particular, the work targeted the optimization of the laser-cooling efficiency in Yb3+ and Tm3+ doped fluorides. The first instance of laser-induced cooling in a Tm3+-doped crystal, BaY2F8 was reported. Cooling by 3 degrees Kelvin below ambient temperature was obtained in a single-pass pump geometry at λ = 1855 nm. Protocols were developed for materials synthesis and purification which can be applied to each component of ZBLANI:Yb3+/Tm3+ (ZrF4 – BaF2 – LaF3 – AlF3 – NaF – InF3: YbF3/TmF3) glass to enable a material with significantly reduced transition-metal impurities. A method for OH- impurity removal and ultra-drying of the metal fluorides was also improved upon. Several characterization tools were used to quantitatively and qualitatively verify purity, including inductively-coupled plasma mass spectrometry (ICP-MS). Here we found a more than 600-fold reduction in transition-metal impurities in a ZrCl2O solution. A non-contact spectroscopic technique for the measurement of laser-induced temperature changes in solids was developed. Two-band differential luminescence thermometry (TBDLT) achieved a sensitivity of ~7 mK and enabled precise measurement of the zero-crossing temperature and net quantum efficiency. Several Yb3+-doped ZBLANI glasses fabricated from precursors of varying purity and by different processes were analyzed in detail by TBDLT. Laser-induced cooling was observed at room temperature for several of the materials. A net quantum efficiency of 97.39±0.01% at 238 K was found for the best ZBLANI:1%Yb3+ laser-cooling sample produced from purified metal-fluoride precursors, and proved competitive with the best commercially procured material. The TBDLT technique enabled rapid and sensitive benchmarking of laser-cooling materials and provided critical feedback to the development and optimization of high-performance optical cryocooler materials. Also presented is an efficient and numerically stable method to calculate time-dependent, laser-induced temperature distributions in solids, including a detailed description of the computational procedure and its implementation. The model accurately predicted the zero-crossing temperature, the net quantum efficiency, and the functional shape of the transients, based on input parameters such as luminescence spectra, dopant concentration, pump properties, and several well-characterized material properties.
Graduation Date: December 2009
URI: http://hdl.handle.net/1928/10315


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