Mercury–Cadmium–Telluride Waveguides – A Novel Strategy for On-Chip Mid-Infrared Sensors

We report the first planar waveguides made from mercury–cadmium–telluride (MCT)a material to date exclusively used for mid-infrared (MIR) detector elementsserving as on-chip MIR evanescent field transducers in combination with tunable quantum cascade lasers (tQCLs) emitting in the spectral regime of 5.78–6.35 μm. This novel MIR sensing approach utilizes structured MCT chips fabricated via molecular beam epitaxy (MBE) as waveguide enabling sensing via evanescent field absorption spectroscopy, as demonstrated by the detection of 1 nL of acetone. Complementary finite difference time domain (FDTD) simulations fit well with the experimentally obtained data and predict an improvement of the limit of detection by at least 2 orders of magnitude upon implementation of thinner MCT waveguides. With the first demonstration of chemical sensing using on-chip MCT waveguides, monolithically fabricated IR sensing systems directly interfacing the waveguide with the MCT detector element may be envisaged

Fast tunable terahertz absorber based on a MEMS-driven metamaterial

We present an experimental study of ultra-thin tunable THz absorbers based on MEMS-driven metamaterials. Using the high mechanical sensitivity of thin subwavelength metamaterial absorbers, we proposed a paradigm to combine meta-atoms and suspended flat membranes to simultaneously maximize the near-field coupling and avoid resonance broadening. We employed a MEMS technology and successfully fabricated THz absorbers based on integration of meta-atoms and MEMS, demonstrating giant tuning of resonant absorption. The devices presented in this paper are among the best-performing tunable THz absorbers achieved to date, particularly in device thickness and tunability characteristics