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The concept of optical refrigeration (also known as laser cooling of solids) was described shortly after the birth of quantum mechanics. Interestingly, it was first rejected by many as unphysical and in violation of the laws of thermodynamics. The underlying mechanism is simple and based on anti-Stokes fluorescence where incident light from a coherent (low entropy) source such as laser is upconverted into high entropy fluorescence via absorption or removal of vibrational energy (phonons). Some have called this phenomenon “a laser running in reverse”. Since its first experimental observation in 1995, optical refrigeration has advanced greatly. Recently, crystals doped with Yb ions have cooled to an absolute temperature of 115K starting from room temperature, with even lower temperatures possible. Optical refrigeration is the only available technique for attaining cryocooling with an entirely solid-state device. In this talk, I will introduce and review the field including the recent efforts leading to net cooling in semiconductor nanostructures.
About the Speaker
Mansoor Sheik-Bahae, Professor of Physics at the University of New Mexico, is the former General Chair of UNM’s Optical Science and Engineering and the Director of Consortium for Laser Cooling in Solids. He obtained his PhD from State University of New York in 1987 and spent seven years at the University of Central Florida as a Research Professor. Professor Sheik-Bahae has received numerous awards. And in 2007, he was recognized for authoring the most cited paper in the history of IEEE Journal of Quantum Electronics regarding the invention of the Z-scan technique. He developed a simple formulation of Kramers-Kr'nig relations for bound-electronic nonlinear optics, and a simple quantum mechanical model for the dispersion and band-gap scaling of the ultrafast optical Kerr effect and nonlinear absorption in optical solids and semiconductors. He was also instrumental in the discovery of large nonlinear phase shifts arising from cascading 2nd order (χ(2):χ(2)) effects. His research includes ultrafast phenomena (e.g. developed the MOSAIC technique for ultrashort pulse characterization), THz plasmonics, but has mostly concentrated on laser cooling of solids (optical refrigeration).
*Times, dates and titles are subject to change. Check mechanical.illinois.edu for updated information. These seminars count toward the requirements for ME 590 and TAM 500.