Mid-infrared suspended waveguide platform and building blocks

In this work, the authors present their recent progress in the development of a platform for the mid-infrared wavelength range, based on suspended silicon waveguides with subwavelength metamaterial cladding. The platform has some intrinsic advantages, which make it a very promising candidate for sensing applications in the molecular fingerprint region. Specifically, it can cover the full transparency window of silicon (up to a wavelength of 8 mu m), only requires one lithographic etch-step and can be designed for strong light-matter interaction. Design rules, practical aspects of the fabrication process and experimental results of a complete set of elemental building blocks operating at two very different wavelengths, 3.8 and 7.7 mu m, are discussed. Propagation losses as low as 0.82 dB/cm at lambda(0) = 3.8 mu m and 3.1 dB/cm at lambda(0) = 7.7 mu m are attained for the interconnecting waveguides.