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Few-cycle, Gapless, and Intense Terahertz Source for Nonlinear Terahertz Spectroscopy
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主讲人: 田传山,复旦大学
地点: 物理楼中楼212
时间: 2023年12月20日 (星期三) 15:10-18:00
主持 联系人: 胡小永(电话:62768705)
主讲人简介: Chuanshan Tian received his B.S. and Ph.D from Fudan university in 2001 and 2006, respectively. From 2006 to 2010, he has been a postdoctoral researcher at Univ. of California at Berkeley. At the end of 2010, he joined the physics faculty at Fudan Univ.. His research interest includes the development of novel surface nonlinear optical spectroscopy and surface science.

Ultrashort energetic terahertz (THz) pulses have opened up exciting new avenues of research in the field of light-matter interactions. For material studies in small laboratories, researchers often require widely tunable femtosecond THz pulses with a peak field strength close to MV/cm. Currently, these pulses can be generated through optical rectification and difference frequency generation in crystals without inversion symmetry. We present in this talk a novel approach for generating THz pulses with no frequency tuning gap. Our method is based on Raman-resonance-enhanced four-wave mixing in centrosymmetric media, specifically diamond. We demonstrate that this technique enables the generation of highly stable, few-cycle pulses with near-Gaussian spatial and temporal profiles. Using a 0.5-mm-thick diamond, we were able to generate THz pulses with a stable and controllable carrier-envelope phase. These pulses carried approximately 15 nJ of energy per pulse at 10 THz, with a peak field strength of about 1 MV/cm at the focus. Experimental measurements of the THz pulse characteristics were in good agreement with theoretical predictions. Furthermore, we discuss additional advantages of our scheme, including the potential for improving the THz output energy to even higher levels.