In the morning of May 8th, Professor Evelyn L.Hu from Harvard University visited Sinano for a exchange program invited by Professor Sun from device department and gave an academic speech on " Ultra-low threshold GaN photonic crystal nanobeam laser ".

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. As a specialist in this area, Professor Lau gave a speech on Ultra-low threshold GaN photonic crystal nanobeam laser (~10 μJ/cm2). The speech focused on the reason that nanobeam laser has ultralow threshold, contenting the rather unusual design of cavity and active layer. Prof. Hu points out that lasers with fQW active layers have thresholds an order of magnitude lower than those with uniform QW active layers because of the extra confinement of photo-generated carriers for fQWs and high carrier capture cross section. Facing four challenges: 1, Material imperfection (threading dislocation and stain); 2, Quantum dots and general materials growth; 3, lack of good cavity fabrication technology; 4, Built-in electric field.

Brief introduction of Prof. Hu: 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 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.