Speakers

Room temperature polariton lasing in radial quantum well nanowires

Chang-Hee_Cho
Chang-Hee Cho
DGIST, Korea
17:30~18:15,November 19th, 2015

Abstract:

Semiconductor nanowires are promising building blocks for coherent light-emitters at the nanoscale, which can be exploited in the fields of nanophotonics, nano-optics and nanobiotechnology. Individual nanowires could serve as an optical waveguide along the axial direction and the high reflectance at the two end facets provides a one-dimensional (1D) Fabry-Perot cavity. Moreover, the light-matter interaction between the excitons and the cavity photons could be enhanced in 1D nanowire geometry because of the enhanced oscillator strength and the reduced mode volume compared to conventional 2D cavities. One of fascinating effects of the light-matter interaction is the low-threshold polariton lasing without the population inversion, resulting from Bose-Einstein condensation of polaritons. Therefore, the 1D polariton in nanowire cavity could be a key to achieve the low-threshold coherent light-emitters at the nanoscale. The lasing mechanism for various material systems, such as GaAs, CdS, and GaN, has been widely investigated to achieve the polariton lasing from nanowire systems. ZnO nanowires are one of the best materials for room temperature polariton lasing because of the strong oscillator strength and the large exciton binding energy (60 meV). However, it is still not clear whether the lasing mechanism in ZnO nanowires at room temperature is attributed to the condensation of 1D polaritons. Also, it is quite difficult to achieve the room temperature polariton lasing in ZnO nanowires because of several limitations such as the low cavity quality factor and thermal broadening of the exciton resonance at room temperature. In this work, the radial ZnO/MgZnO quantum wells, which could provide the larger oscillator strength and more stable exciton at room temperature, was introduced to achieve the room temperature polariton lasing in ZnO nanowires. The radial quantum well nanowires exhibited the outstanding features, including the thermal stability of polaritons up to the room temperature, ultra-low lasing threshold, and high spectral coherence. The characteristic features of room temperature polariton lasing will be presented.

 

 

Research Interests:

Since the optoelectronic technologies cover a wide range of human life including optical data processing (computing), lighting, renewable energy sources, environmental- and bio-technologies, it is essential to explore new science and functionalities in novel optoelectronic materials such as quantum, nanophotonic, and plasmonic/meta-materials of which the properties are based on light-matter interactions. The research in Nanoscale Optoelectronic Materials Laboratory focuses on finding novel optoelectronic properties, designing materials, and developing advanced optoelectronic devices.

 

 

Professional Activities:

  • 2012.9-present Assistant Professor, Dept. of Emerging Materials Science, DGIST, Daegu, Korea
  • 2009.9-2012.8 Postdoctoral Researcher, Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA
  • 2009.8 Ph. D. Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Korea
  • 2004.2 M. S. Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Korea
  • 2002.2 B. S. Physics, Kyung Hee University, Seoul, Korea