Probing Light-Matter Interactions in Polar Semiconductor Materials


【讲座题目】Probing Light-Matter Interactions in Polar Semiconductor Materials



【主 讲 人】熊启华 教授


熊启华是南洋理工大学数理科学学院和电气电子工程学院双聘教授。他1997年本科毕业于武汉大学物理系,2006年于宾夕法尼亚州立大学获得博士学位,师从Peter C. Eklund教授。2006-2009年在哈佛大学Charles Lieber研究组从事博士后研究。2009年加入南洋理工大学, 2014年获得终身教职,2016年升正教授。他于2014年起担任数理科学学院副院长主管科研, 研究生教学,2017年起主要负责教职事务。熊教授的主要研究领域是以稳态和瞬态光谱学为主要实验手段,以光和物质相互作用为研究主题, 着重研究低维半导体纳米材料基于光子-声子-电子耦合作用的物理机制和量子调控。在《自然》及子刊, 《纳米通讯》,《先进材料》等一系列国际知名杂志上发表了180多篇文章, 并被世界知名杂志及大众媒体所报道,总引用次数超过6500余次,H-因子48。获新加坡物理学会纳米科技奖(2015),新加坡国立研究基金NRF Investigatorship奖(2014)等。


The interaction of light with matter gives rises to a wide range of linear and nonlinear phenomena that we are familiar with, such as absorption and scattering, spontaneous or stimulated emission, and second harmonic generation. In polar semiconductors, the electromagnetic field of light polarizes the matter leading to the formation of elemental excitations such as excitons and exciton polaritons, due to long-range dipolar force as well as additional coupling to the optical fields. In this talk, I will first introduce the background of exciton, exciton polaritons and the electron/exciton-longitudinal optical phonon (LOP) interactions in semiconductors. I will then present the first fluorescence laser cooling of semiconductors based on cadmium sulfide nanoribbons, enabled by enhanced strong exciton-LOP coupling at nanoscale. In zinc telluride nanoribbons, resolved-sideband Raman cooling of LOPs can be realized with a similar physical picture of cavity optomechanics, in which the excitonic mode was utilized to assist the photoelastic Raman scattering from the LOPs. By detuning the laser pumping, the dipole oscillation of the LOPs is photoelastically attenuated (enhanced) to a colder (hotter) state, corresponding to the laser cooling of amplification of the LOPs respectively. Finally, I will introduce our recent work on strong light-matter coupling in all-inorganic perovskite crystals embedded in optical microcavities. Those prototype semiconductors have exceptionally large exciton binding energy, strong oscillator strength and facile epitaxy-free growth. Room temperature exciton polariton lasing can be realized, which was unambiguously evidenced by a superlinear power dependence, macroscopic ground state occupation, blueshift of ground state emission, and the build-up of long-range spatial coherence, suggesting considerable promise of room temperature polariton devices and coherent light sources extending from the ultraviolet to near infrared range. Future work will be briefly discussed, with a particular interest on transient spectroscopy investigations of semiconductors.