The participants in the Consortium for Laser Cooling in Solids will explore the fundamental and practical issues of laser cooling in semiconductors and rare-earth doped solids.  The anticipated advances from this MURI supported research will enable the deployment of optical refrigerators in USAF Space Vehicles and in other DoD missions.  Optical refrigeration is a new approach to cooling that involves no moving parts or fluids, in contrast to existing cryogenic refrigeration technology.  High performance laser cooling will allow construction of compact, rugged, all solid-state devices that are vibration-free and immune from electromagnetic interference.  Long lifetime, low mass, and high reliability make laser cooling particularly well suited for space-based applications. 

The University of New Mexico (UNM) and its collaborators are recognized world leaders in the science of laser cooling of solids and have established many significant milestones in the field.  We demonstrated the record amount of cooling (DT = 75K) and record amount of cooling power (~ 75 mW) in rare-earth doped materials.  This work has been reported in prestigious scientific journals and at prominent international conferences. Our achievements in laser cooling of solids, both experimental and theoretical, are unrivaled anywhere in the world.  For this MURI program, hawse have assembled a multi-disciplinary team of dedicated, creative, and distinguished scientists. Participants are from the Department of Physics and Astronomy (PA) and the Center for High Technology materials (CHTM) at UNM, The University of Arizona (UA), and Johns Hopkins University (JHU)  This consortium can attack all the current, key issues in laser cooling of solids and make rapid advances in this valuable technology.

In the area of semiconductor cooling, years of work have allowed us to identify the critical obstacles that must be overcome to realize net cooling.   At CHTM/UNM, we will grow bulk and quantum-confined heterostructures with the high quantum efficiencies needed for laser cooling. We will build devices at P&A/UNM that remove heat-producing luminescence via bonded-dome and nanogap schemes. To diagnose and characterize the physics, we will use time-resolved photoluminescence, infrared emissivity, and Mach-Zehnder interferometric techniques.  The growth of heterostructures will be guided by theoretical work at UA.  These studies will determine the cooling efficiencies of reduced-dimensional structures along with the effects of crystal strain and band-gap engineering. Theoretical efforts at JHU will examine novel approaches to luminescence management such as the use of omni-directional mirrors and photonic bandgap materials.

In the area of rare-earth doped glasses and crystals, we will develop materials that cool at lower temperatures with higher efficiencies. We will integrate these into units that have good thermal coupling to cooled devices with low parasitic heat loads. Our analysis indicates there are no fundamental limits preventing such materials from cooling to 80 K or lower. We will construct a prototype device to cool a cryogenic infrared photosensor.