Suspended microracetrack resonator with lateral sub-wavelength-grating metamaterial cladding for mid-infrared sensing applications

• Main Authors: Zhang, Zecen, Ng, Geok Ing, Hu, Ting, Qiu, Haodong, Guo, Xin, Wang, Wanjun, Mohamed Saïd Rouifed, Liu, Chongyang, Sia, Jiaxu, Zhou, Jin, Wang, Hong
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Electrical and electronic engineering; Mid-infrared Sensing; Metamaterial Cladding
• Online Access: https://hdl.handle.net/10356/137622
• Institution: Nanyang Technological University

A one-time etching suspended microracetrack resonator with lateral sub-wavelength-grating (SWG) metamaterial cladding is theoretically and experimentally demonstrated on commercial 340 nm-thick-top-silicon silicon-on-insulator (SOI) platform for mid-infrared (MIR) bio-chemical sensing applications. The suspended structure can offer a larger exposed area of waveguides with the testing chemicals as well as a decent sensitivity. And the one-time etching process also eases the fabrication. The suspended waveguide is optimized with a balance between propagation loss and the sensitivity. The suspended microracetrack resonator is experimentally measured at 2 μm wavelength and well fitted with an extinction ratio (ER) of 12.3 dB and a full-width-at-half-maximum (FWHM) of 0.12 nm, which corresponds to a quality factor (Q factor) of 16600. With the equivalent refractive index method and a specially developed numerical model, the expected sensitivities of fundamental TE and TM mode were calculated as 58 nm/RIU and 303 nm/RIU respectively. This one-time etching suspended microracetrack resonator shows great potential in MIR optical bio-chemical sensing applications.