Pump‐Color Selective Control of Ultrafast All‐Optical Switching Dynamics in Metaphotonic Devices

• Published in: Advanced science Vol. 7; no. 14; pp. 2000799 - n/a
• Main Authors: Hu, Yuze, You, Jie, Tong, Mingyu, Zheng, Xin, Xu, Zhongjie, Cheng, Xiangai, Jiang, Tian
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 01.07.2020; John Wiley and Sons Inc; Wiley
• Subjects: electromagnetically induced transparency; germanium; Light; Semiconductors; silicon; terahertz metamaterials; ultrafast photoswitching
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202000799

Incorporating active materials into metamaterials is expected to yield exciting advancements in the unprecedented versatility of dynamically controlling optical properties, which sheds new light on the future optoelectronics. The exploration of emerging semiconductors into terahertz (THz) meta‐atoms potentially allows achieving ultrafast nanodevices driven by various applications, such as biomedical sensing/imaging, ultrawide‐band communications and security scanners. However, ultrafast optical switching of THz radiation is currently limited to a single level of tuning speed, which is a main hurdle to achieve multifunctionalities. Here, a hybrid metadevice which can realize the pump‐wavelength controlled ultrafast switching response by the functionalization of double photoactive layers is demonstrated experimentally. A whole cycle of electromagnetically induced transparency switching with a half‐recovery state changes from 0.78 ns to 8.8 ps as pump wavelength varies from near infrared to near ultraviolet regions. The observed pump‐color selective switching speed changing from nanosecond scale to picosecond scale is ascribed to the wavelength‐dependent penetration length of Ge and the contrasting defect states between noncrystalline Ge and epitaxial Si layers. It is believed that the schemes regarding pump‐color controllable ultrafast switching behavior introduced here can inspire more innovations across the field of ultrafast photonics and can boost the reconfigurable metamaterial applications. All‐optical terahertz modulators with pump‐color selective ultrafast switching speed are realized by combining double layers of semiconductors with electromagnetically induced transparency meta‐atoms. The transmission/group delay of terahertz wave is modulated at contrasting switching speeds from sub‐nanoseconds to picoseconds when pumped by the near‐infrared and near‐ultraviolet beams. This work opens up new avenues for manipulating the dynamics of ultrafast metaphotonic devices.