Aluminium, gold-tin and titanium-tungsten alloys for mid-infrared plasmonic gratings

The field of mid-infrared (MIR) plasmonics has shown great potential applications in spectroscopic sensing, infrared light sources and detectors. MIR plasmonic materials that are compatible with common fabrication processes may enable cost-effective and reliable plasmonic device platforms. In this work, we examined aluminium metal (Al), gold-tin (AuSn) and titanium-tungsten (TiW) alloys regarding their usability for surface plasmon polariton (SPP) excitation in the MIR regime using a grating configuration. The angle dependence and the influence of varying depths of gratings were numerically and experimentally studied for the chosen materials. The structures were fabricated on eight-inch silicon (Si) substrates and characterized with a free-beam reflection measurement setup in the MIR regime. The fabricated gratings show narrow resonance dips, which are in good agreement with the simulations, revealing that Al, AuSn and TiW alloys are reliable plasmonic materials for MIR plasmonic devices.