Lee Sang-Hun, Kim Moohyuk, Roh Yeeun, Kim Myung-Ki, Seo Minah
Department of Optical Engineering, Kumoh National Institute of Technology, 350-27, Gumidae-ro, Gumi, Gyeongbuk, 39253, Republic of Korea.
KU-KIST Graduate School of Converging Science and Technology, Korea University, Anam-ro 145, Seongbuk-gu, Seoul, 02841, Republic of Korea.
Adv Sci (Weinh). 2025 Jan;12(1):e2405225. doi: 10.1002/advs.202405225. Epub 2024 Nov 4.
Ongoing efforts spanning decades aim to enhance the efficiency of optical devices, highlighting the need for a pioneering approach in the development of next-generation components over a broad range of electromagnetic wave spectra. The nonlinear transport of photoexcited carriers in semiconductors at low photon energies is crucial to advancements in semiconductor technology, communication, sensing, and various other fields. In this study, ultra-low threshold resonance mode switching by strong nonlinear carrier transport beyond the semi-classical Boltzmann transport regime using terahertz (THz) electromagnetic waves are demonstrated, whose energy is thousands of times smaller than the bandgap. This is achieved by employing elaborately fabricated 3D tip structures at the nanoscale, and nonlinear effects are directly observed with the THz resonance mode switching. The nanotip structure intensively localizes the THz field and amplifies it by more than ten thousand times, leading to the first observation of carrier multiplication phenomena in these low-intensity THz fields. This experimental findings, confirmed by concrete calculations, shed light on the newly discovered nonlinear behavior of THz fields and their strong interactions with nanoscale structures, with potential implications and insights for advanced THz technologies beyond the quantum regime.
数十年来的持续努力旨在提高光学器件的效率，这凸显了在广泛的电磁波谱范围内开发下一代组件时采用开创性方法的必要性。低光子能量下半导体中光激发载流子的非线性输运对于半导体技术、通信、传感及其他各个领域的进步至关重要。在本研究中，展示了利用太赫兹（THz）电磁波在超越半经典玻尔兹曼输运 regime 的情况下通过强非线性载流子输运实现的超低阈值共振模式切换，其能量比带隙小数千倍。这是通过采用精心制造的纳米级三维尖端结构实现的，并且通过太赫兹共振模式切换直接观察到了非线性效应。纳米尖端结构密集地使太赫兹场局部化并将其放大一万多倍，从而首次在这些低强度太赫兹场中观察到载流子倍增现象。这些实验结果经具体计算得到证实，揭示了新发现的太赫兹场的非线性行为及其与纳米级结构的强相互作用，对量子 regime 之外的先进太赫兹技术具有潜在的影响和启示。
