Achieving Cryogenic Temperature in Laser Cooling Using Ion-Doped Nanopowders

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ABSTRACTNational Science FoundationProposal Number CTS-0553651Principal Investigator Kaviany, MassoudAffiliation University of MichiganProposal Title Achieving Cryogenic Temperature in Laser Cooling Using Ion-Doped NanopowdersLaser cooling of solid is achieved as the medium emits light at a shorter wavelength than that it absorbs, with the excess energy provided by the annihilation of lattice phonons. This technique has the potential to develop an all solid-state cryocooler for a variety of applications such as sensor cooling. To date, solids have been cooled from room temperature to 208 K (temperature difference T = 92K). We propose to enhance the cooling performance using nanopowders, to T = 170 K. Absorption is increased by (a) increasing the population of participating electrons through dopant concentration optimization, (b) increasing the number of photons in the interacting volume by photon localization in nanopowders, and (c) increasing the number of participating phonons by phonon density of states optimization using nanoparticle size effect. This enhanced laser cooling performance will be demonstrated by a combined theoretical, computational and experimental investigation. To our knowledge, this will be the first attempt of laser cooling in nanostructured solids, and the first time to bring laser cooling performance to cryogenic temperature range. With respect to Broader Impacts, the emergence of nanotechnology has increased the science content of the engineering research and education. This proposed project is part of the PI's continuous and systematic effort to include more physical fundamentals into an integrated and current academic research-education program in heat transfer.