High-Q germanium optical nanocavity
Mid-infrared (MIR) integrated photonics has attracted broad interest due to its promising applications in biochemical sensing, environmental monitoring, disease diagnosis, and optical communication. Among MIR integration platforms, germanium-based platforms hold many excellent properties, such as wide transparency windows, high refractive indices, and high nonlinear coefficients; however, the development of MIR germanium photonic devices is still in its infancy. Specifically, MIR high-Q germanium resonators with comparable performance to their silicon counterparts remain unprecedented. Here we experimentally demonstrate an MIR germanium nanocavity with a Q factor of ～18,000, the highest-to-date of reported nanocavities across MIR germanium-based integration platforms. This is achieved through a combination of a feasible theoretical design, Smart-Cut methods for wafer development, and optimized device fabrication processes. Our nanocavity, with its high Q factor and ultrasmall mode volume, opens new avenues for on-chip applications in the MIR spectral range.
基金项目：Konica Minolta Imaging Science Encouragement Award; Ministry of Education, Culture, Sports, Science and Technology (MEXT)10.13039/501100001700; Japan Society for the Promotion of Science (JSPS)10.13039/501100001691 (JP26220605, JP18K13798); New Energy and Industrial Technology Development Organization (NEDO)10.13039/501100001863; Burroughs Wellcome Foundation.
Ziqiang Zhao：Department of Electrical Engineering and Information Systems, The University of Tokyo, Tokyo 113-0033, Japan
Wen Zhou：Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
Mitsuru Takenaka：Department of Electrical Engineering and Information Systems, The University of Tokyo, Tokyo 113-0033, Japan
Hon Ki Tsang：Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
Zhenzhou Cheng：Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
Keisuke Goda：Department of Chemistry, The University of Tokyo, Tokyo 113-0033, JapanDepartment of Electrical Engineering, University of California, Los Angeles, California 90095, USAe-mail: firstname.lastname@example.org
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Ting-Hui Xiao, Ziqiang Zhao, Wen Zhou, Mitsuru Takenaka, Hon Ki Tsang, Zhenzhou Cheng, and Keisuke Goda, "High-Q germanium optical nanocavity," Photonics Research 6(9), 925-928 (2018)