| 报告题目 | Laser Cooling of Semiconductors |
| 报告人 | Prof. Qihua Xiong |
| 报告人单位 | Nanyang Assistant Professor and Fellow of Singapore National Research Foundation School of Physical and Mathematical Sciences, Nanyang Technological University |
| 报告时间 | 2014-01-07 |
| 报告地点 | 合肥微尺度物质科学国家实验室一楼科技展厅 |
| 主办单位 | 合肥微尺度物质科学国家实验室、中国科学技术大学化学与材料科学学院 |
| 报告介绍 | 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 ~110 K cooling from ambient, surpassing the thermoelectric Peltier cooler. On the other hand, it would be more tantalizing to realize laser cooling in direct band-gap semiconductors. Semiconductors exhibit more efficient pump light absorption, much lower achievable cooling temperature and direct integrability into electronic and photonic devices. However, so far no net-cooling in semiconductors has been achieved despite of many experimental and theoretical efforts in the past few decades. In this presentation, we demonstrate the first net laser cooling in semiconductors using cadmium sulfide (CdS) nanobelt facilitated by multiple longitudinal optical phonon assisted upconversion due to strong and enhanced Fröhlich interactions. Under a low power excitation, we have achieved a ~40 K and ~20 K net cooling in CdS nanobelts starting from 290 K pumped by 514 nm and 532 nm lasers, respectively. Our findings suggest alternative II-VI semiconductors for laser cooling and may find promising applications 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. At last, our progress in bulk crystal synthesis will be discussed within the context of realizing scalable devices for optical refrigeration applications.
报告人简介： |
