Mid-infrared Fourier-transform spectrometer based on metamaterial lateral cladding suspended silicon waveguides
Thi Thuy Duong Dinh, Xavier Le Roux, Natnicha Koompai, Daniele Melati, Miguel Montesinos‐Ballester, David González‐Andrade, Pavel Cheben, Aitor V. Velasco, Éric Cassan, Delphine Marris‐Morini, Laurent Vivien, Carlos Alonso-Ramos
Abstract
Integrated mid-infrared micro-spectrometers have a great potential for applications in environmental monitoring and space exploration. Silicon-on-insulator (SOI) is a promising platform to tackle this integration challenge, owing to its unique capability for large volume and low-cost production of ultra-compact photonic circuits. However, the use of SOI in the mid-infrared is restricted by the strong absorption of the buried oxide layer for wavelengths beyond 4 µm. Here, we overcome this limitation by utilizing metamaterial-cladded suspended silicon waveguides to implement a spatial heterodyne Fourier-transform (SHFT) spectrometer operating at wavelengths near 5.5 µm. The metamaterial-cladded geometry allows removal of the buried oxide layer, yielding measured propagation loss below 2 dB/cm at wavelengths between 5.3 and 5.7 µm. The SHFT spectrometer comprises 19 Mach–Zehnder interferometers with a maximum arm length imbalance of 200 µm, achieving a measured spectral resolution of 13 cm −1 and a free spectral range of 100 cm −1 at wavelengths near 5.5 µm.