Suspended silicon waveguides for long-wave infrared wavelengths

• Main Authors: Sánchez-Postigo, A., Nedeljkovic, M., Ortega-Moñux, A., Wangüemert-Pérez, J. G., Xu, Y., Halir, R., Qu, Z., Khokhar, A. Z., Osman, A., Cao, W., Littlejohns, Callum G., Cheben, P., Molina-Fernández, I., Mashanovich, G. Z., Penadés, J. Soler
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2019
• Subjects: Silicon Photonics; Mid-infrared; DRNTU::Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/85326; http://hdl.handle.net/10220/48192
• Institution: Nanyang Technological University

In this Letter, we report suspended silicon waveguides operating at a wavelength of 7.67 μm with a propagation loss of 3.1±0.3 dB/cm. To our knowledge, this is the first demonstration of low-loss silicon waveguides at such a long wavelength, with loss comparable to other platforms that use more exotic materials. The suspended Si waveguide core is supported by a sub-wavelength grating that provides lateral optical confinement while also allowing access to the buried oxide layer so that it can be wet etched using hydrofluoric acid. We also demonstrate low-loss waveguide bends and s-bends.