Suspended germanium waveguides with subwavelength-grating metamaterial cladding for the mid-infrared band
Alejandro Sánchez‐Postigo, Alejandro Ortega‐Moñux, Jordi Soler Penadés, Ahmed Osman, Miloš Nedeljković, Zhibo Qu, Yangbo Wu, Íñigo Molina‐Fernández, Pavel Cheben, Goran Z. Mashanovich, J. Gonzalo Wangüemert‐Pérez
Abstract
In recent years, sensing and communication applications have fueled important developments of group-IV photonics in the mid-infrared band. In the long-wave range, most platforms are based on germanium, which is transparent up to ∼15-µm wavelength. However, those platforms are limited by the intrinsic losses of complementary materials or require complex fabrication processes. To overcome these limitations, we propose suspended germanium waveguides with a subwavelength metamaterial lateral cladding that simultaneously provides optical confinement and allows structural suspension. These all-germanium waveguides can be fabricated in one dry and one wet etch step. A propagation loss of 5.3 dB/cm is measured at a wavelength of 7.7 µm. These results open the door for the development of integrated devices that can be fabricated in a simple manner and can potentially cover the mid-infrared band up to ∼15 µm.