Ultra-low threshold GaN photonic crystal nanobeam laser
Prof. Evelyn L. Hu
Tarr-Coyne Professor of Applied Physics and Electrical Engineering
School of Engineering and Applied Sciences
Harvard University
HKUST Jockey Club Institute of Advanced Study Visiting Professor
Hoster：Prof. Qian Sun
Time: Friday 10:45 -12:00a.m., 8th May.
Place: D111 SINANO
Abstract:
GaN-based materials are well-recognized for their exceptional optical qualities, particularly in the blue and UV parts of the spectrum. In addition, their wide bandgaps allow efficient operation at room temperature and higher. Cavities that are engineered at the nanoscale can bring out the most efficient operation of the GaN-based active layer material. This work will describe the room-temperature performance of optically-pumped GaN photonic crystal (PC) nanobeam lasers, with thresholds as low as 9.1 μJ/cm2, the lowest power densities recorded in this material system.
The low thresholds result from the very low photon loss and high field confinement of the cavity structure and the high spontaneous emission factor, β = 0.94. A key factor in achieving the low threshold is the rather unusual active layer: Indium Gallium Nitride (InGaN) fragmented quantum well (fQWs). Lasers with fQW active layers have thresholds an order of magnitude lower than those with uniform QW active layers. We believe that the extra confinement of photo-generated carriers for fQWs and high carrier capture cross section is responsible for the excellent performance.
Bio:
After receiving her PhD in Physics from Columbia University, Prof Evelyn Hu worked at AT&T Bell Laboratories from 1975 to 1984. She was Professor in the Departments of Electrical & Computer Engineering, and Materials at the University of California, Santa Barbara from 1984-2008. She served as the scientific co-director of the California NanoSystems Institute, a joint initiative at UCSB and the University of California, Los Angeles. She is currently the Tarr-Coyne Professor of Applied Physics and Electrical Engineering in Harvard's School of Engineering and Applied Sciences. She was awarded a Doctor of Engineering honoris causa from the Hong Kong University of Science and Technology in 2013.
Prof Hu’s research focuses on high-resolution fabrication of compound semiconductor electronic and optoelectronic devices, candidate structures for the realization of quantum computation schemes, and on novel device structures formed through the heterogeneous integration of materials. She has also developed biological approaches to the formation of electronic and photonic materials.
Prof Hu is a member of the US National Academy of Sciences, US National Academy of Engineering, the American Academy of Arts and Sciences, the Academia Sinica of Taiwan, and the JASON Project. She is also a Fellow of the IEEE, the American Physical Society, and the American Association for the Advancement of Science. She has been a recipient of an NSF Distinguished Teaching Fellow award and an AAAS Lifetime Mentor Award, and holds an honorary Doctorate of Engineering from the University of Glasgow.
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