On the afternoon of June 5, 2023, Professor She Weilong from the School of Physics at Sun Yat-sen University was invited to DGUT for academic exchanges and delivered an academic report titled "What Is the Meaning of the Physical Quantity v in the Photon Energy Expression hv?" The session was held in Conference Room A10 of the Interdisciplinary Science Research Center and was chaired by Professor Wang Biao, Dean of the School of Materials Science and Engineering. The report was conducted in a hybrid format combining online and in-person participation, with dozens of faculty members and graduate students from the School of Materials Science and Engineering, the School of Microelectronics, and other units attending.

Beginning with the well-known photoelectric effect, the report raised the question of whether the stopping voltage in the photoelectric effect is determined by the central wavelength or the shortest wavelength. Professor She then introduced the historical development of the light quantum concept and its wide-ranging applications in fields involving light-matter interactions such as particle physics, quantum optics, spectroscopy, and optoelectronics. Subsequently, drawing on over forty years of research experience, Professor She provided an in-depth exposition covering the quantum optical model of the photon and its limitations, the assertion that monochromatic plane light waves and truncated sinusoidal light waves are not fundamental building blocks of light fields, the effect of photon absorption on light waves, the discrete wavelet structure of plane light wave trains, and discrete energy considerations. Finally, by integrating both theoretical and experimental perspectives, he demonstrated that the physical quantity v in the photon energy expression hv refers to the central frequency of the light wave train spectrum rather than the frequency of a monochromatic light wave. He further showed that across the visible and near-infrared regions, the spectral bandwidth of a light wave train can reach 122 nm, meaning that a single photon can correspond to a light wave bandwidth of up to 122 nm.

After the report, the attending faculty members engaged in lively exchanges and discussions with Professor She Weilong on topics including the details of linear absorption experiments, wavelet transforms, and the correlation between phonons and photons.

Introduction to Professor She Weilong:

Professor She Weilong holds a Ph.D. in Science (Optics) and is a Second-Level Professor and doctoral supervisor at Sun Yat-sen University. He is a recipient of the State Council Special Government Allowance. From 2000 to 2016, he served as Director of the Institute of Laser and Spectroscopy at Sun Yat-sen University, and he served a term as a member of the Academic Committee of Sun Yat-sen University. He entered the Department of Physics at Sun Yat-sen University in March 1978, majoring in Optics, and graduated with a bachelor's degree in February 1982. He was then assigned to the Shanghai Institute of Ceramics, Chinese Academy of Sciences, where he conducted research on the optical properties of synthetic crystals. In September 1987, he enrolled in the Graduate School of Sun Yat-sen University to pursue a master's degree, and in September 1989, he advanced to doctoral studies, earning his Ph.D. in July 1992. Upon graduation, he remained at Sun Yat-sen University, working at the State Key Laboratory of Ultrafast Laser Spectroscopy (later renamed the State Key Laboratory of Optoelectronic Materials and Technologies) and also at the School of Physics and Engineering Technology (later reorganized as the School of Physics). He was promoted to Associate Professor in 1994 and to Professor in 1998, and was qualified as a doctoral supervisor in the same year. He has supervised 52 doctoral and master's graduates. Since his master's and doctoral studies, his research has focused on nonlinear optics, optical physics (optical momentum and optical angular momentum), and quantum optics. He has published over 150 academic papers, including 3 in the world-leading physics journal Physical Review Letters, 1 in Physical Review A (Rapid Communications), 4 in Physical Review A, 2 in Physical Review E, 9 in Optics Letters, and 11 in Optics Express. He has received a Second Prize in Natural Sciences of the National Science and Technology Award nominated by the Ministry of Education, two Third Prizes of the Guangdong Provincial Natural Science Award, one Third Prize of the Guanghua Science and Technology Achievement Award, one First Prize for Outstanding Natural Science Papers of Guangdong Province, and one First Prize for Outstanding Scientific and Technological Papers of Guangzhou Municipality. He has co-authored one book on advances in nonlinear optics in both Chinese and English editions, and authored the entry entitled "The Nature of Light" for the physics volume of "1000 Scientific Challenges."

Draft: Wen Donghui

First Review: Liu Zhao / Second Review: Li Runxia / Third Review: Wang Biao