新加坡南洋理工大学Qihua Xiong教授来访

2015-12-1 19:23:59

报告题目Laser Cooling of Semiconductors: II-VI Nanoribbons and organic-Inorganic Perovskite Crystals

报告人Qihua Xiong (Associate Professor, Nanyang Technological University)

报告时间127日(星期1430

报告地点:物理科技楼101

报告摘要

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 ~100 K cooling from ambient, surpassing the thermoelectric Peltier cooler. On the other hand, attempts of laser cooling of semiconductors based on III-V quantum wells have led to very minimum progress in the past twenty years. In this talk, I will present the background of laser cooling of solids, and our recent breakthrough of 40 Kelvin laser cooling of semiconductors in II-VI semiconductors in nanoribbon morphology. The laser cooling is achieved by longitudinal optical phonon assisted photoluminescence upconversion. Recently, we have discovered another big family of materials, i.e., 2D and 3D organic-inorganic perovskite crystals for laser cooling, enabled by extremely high external quantum efficiency. Our work advocates the great promises of II-VI semiconductors and perovskites for optical refrigeration with the advantage of compactness, vibration- and cryogen-free, high reliability and direct integrability into nanoscale electronic and photonic devices.

References

1) S.T. Ha, C. Shen, J. Zhang and Q.H. Xiong*, “Laser Cooling of organic-inorganic Lead Halide Perovskites”, Nature Photonics, accepted (2015)

2) D.H. Li, J. Zhang, X.J. Wang, B.L. Huang and Q.H. Xiong*, “Solid-State Semiconductor Optical Cryocooler Based on CdS Nanobelts”, Nano Lett.14, 4724–4728 (2014)

3) D.H. Li, J. Zhang and Q.H. Xiong*, “Laser cooling of CdS nanobelts: Thickness matters”, Opt. Express21, 19302-19310 (2013)

4) J. Zhang, D.H. Li, R.J. Chen and Q.H. Xiong*, “Laser cooling of a semiconductor by 40 Kelvin”, Nature493, 504-508 (2013) (Cover Highlight, highlighted by Nature Photonics in its April and May issues, news coverage by German Public Radio, German Science News, Physics world by IoP, Txchnologist, Arstechnia, The Statesman-The Oldest English Newspaper of India, Wiley Materials Views China, Phys org, Channel Asia, The Strait Times, and so forth)


报告人简介

Qihua Xiong received his B.S. degree in physics from Wuhan University in 1997, and then finished three years graduate studies at the Shanghai Institute of Applied Physics, Chinese Academy of Sciences. He went to the United States in 2000 and received a Ph.D. degree under the supervision of Prof. Peter C. Eklund from The Pennsylvania State University in 2006. After three years postdoctoral experience in Prof. Charles M. Lieber’s group at Harvard University, he joined Nanyang Technological University as an assistant professor in 2009 and promoted to Nanyang Associate Professor in 2014. He is a Fellow of Singapore National Research Foundation awarded in 2009. He has been recently awarded the prestigious Nanyang Award for research excellence and the NRF Investigatorship Award by Singapore National Research Foundation. Prof. Xiong’s research focuses on light-matter interactions of emergent quantum matter by optical spectroscopy approaches. He recently ventured into the field of 2D layered materials and laser cooling of solids.


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