Prof. Zefeng Wang
Prof. Zefeng Wang
National University of Defense Technology (NUDT), China
Title: Fiber gas Raman lasers
Fiber lasers have wide potential applications, and are increasingly replacing traditional solid state and gas lasers in many applications due to their compactness, high efficiencies, excellent beam qualities and convenient heat management. However, due to the low damage threshold, solid-core fiber lasers lack the ability to provide the same power levels as conventional gas lasers, which can reach MW levels in chemical gas lasers; Because of nonlinear effects, the spectral linewidth of light generated in silica fibers will broaden at high powers; As the number of rare earth materials is limited, only certain laser wavelengths are available; Due to the strong infrared absorption of silica fibers, it is difficult to obtain laser wavelength beyond 3 μm. Gas stimulated Raman scattering (SRS) has been demonstrated to be an effective method to obtain high-power narrow-linewidth lasers of otherwise unobtainable wavelengths, especially in the ultra-violet and mid-infrared spectral range. In traditional gas cells the effective interaction length is very short and the system can be bulky and cumbersome, limiting the applications of these lasers. The advent of anti-resonance hollow-core fibers and their properties of long effective interaction length, high optical confinement, and the possibility of control of the effective gain spectrum make it possible to develop a novel type of laser, named fiber gas Raman lasers, which combines the advantages of both fiber and gas lasers. By properly designing the transmission bands of hollow-core fibers, selecting active gases and pump sources, fiber gas Raman lasers can potentially provide a wide range of emission wavelengths from the UV to the IR pumped with commercial 1μm lasers. Owing to the nature of transitions in atomic and molecular gases, fiber gas Raman lasers are spectrally narrow even without additional linewidth limiting measures. We have demonstrated efficient high-power, narrow-linewidth 1.5 μm, 2 μm and 3 μm fiber gas Raman lasers using hollow-core fibers filled with different gases from 1064 nm solid-state lasers. Our work provides a very possible way to obtain high-power, narrow-linewidth mid-infrared fiber lasers by gas stimulated Raman scattering in hollow-core fiber pumped with normal 1μm lasers.
Wang Zefeng received Doctor degree in fiber information technology from the National University of Defense Technology (NUDT) in 2008. He visited Bath University in UK from October 2012 to July 2014. He is currently an associate professor with College of Advanced Interdisciplinary Studies, NUDT. He has published more than 100 journal and conference papers. His research interests cover mainly fiber gas laser, hollow-core fiber and fiber gratings.