Laser Cooling of Semiconductors: Next Generation Optical Refrigeration
Nanyang Associate Professor and Fellow of Singapore National Research Foundation
School of Physical and Mathematical Sciences,
Nanyang Technological University
Email Address: Qihua@ntu.edu.sg.
Optical irradiation accompanied by spontaneous anti-Stokes emission can lead to cooling of matter, a phenomenon known as laser cooling or optical refrigeration proposed in 1929 by Peter Pringsheim. In solid state materials, the cooling is achieved by annihilation of lattice vibrations (i.e., phonons). Since the first experimental demonstration in rare-earth doped glasses, considerable progress has been made particularly in ytterbium-doped glasses or crystals with a recent record of ~110 K cooling from ambient, surpassing the thermoelectric Peltier cooler. Rare-earth doped materials remain to be the only candidate in the toolbox of laser cooling for the past few decades until our recent discovery in the laser cooling of group II-VI semiconductors CdS in nanobelt morphology. Nevertheless, the toolbox of laser cooling is still very limited, practical applications in optical refrigeration demand more suitable and scalable materials for laser cooling. This talk will present the background of laser cooling of solids, and our recent progress in searching bulk and scalable materials particularly in bulk II-VI semiconductors and organic-inorganic perovskite thin films for laser cooling towards next generation optical refrigeration applications, which have great promises in the field of cryogenics with the advantage of compactness, vibration- and cryogen-free, high reliability and direct integrability into nanoscale electronic and photonic devices.
1. D.H. Li, J. Zhang and Q.H. Xiong*, “Laser cooling of CdS nanobelts: Thickness matters”, Opt. Express 21, 19302-19310 (2013)
2. J. Zhang, D.H. Li, R.J. Chen and Q.H. Xiong*, “Laser cooling of a semiconductor by 40 Kelvin”, Nature 493, 504-508 (2013) (Nature Cover Highlight, highlighted by Nature Photonics in its April and May issues).
3. S.T. Ha, X.F. Liu, Q. Zhang, D. Giovanni, T.C. Sum and Q.H. Xiong*, “Synthesis of organic-inorganic lead halide perovskite nanoplatelets: Towards high performance perovskite solar cells and opto-electronic devices”, Adv. Optical Mater. 2, 838-844 (2014) (Highlighted as the Frontispiece).
4. Q. Zhang, S.T. Ha, X.F. Liu, T.C. Sum and Q.H. Xiong*, “Room-Temperature Near-Infrared High-Q Perovskite Whispering-Gallery Planar Nanolasers”, Nano Lett. 14, 5995–6001 (2014).