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Abstract

Highly doped group IV semiconductors such as Ge or GeSn are promising candidates for plasmonic mid infrared applications. The lower effective mass of GeSn alloys in comparison to pure Ge can result in lower plasma wavelengths and extend the application wavelength range. Devices made from doped GeSn alloys, therefore, are one interesting route towards plasmonic applications in the mid-infrared wavelength range, possibly extending to the NIR. Here, we specifically explore how spectrally narrow plasmonic resonances can be obtained in comb-like grating antennas by combining aspects of material growth with geometry optimization. We investigate both in simulation and in experiment how the interplay of localised surface plasmon resonances and Rayleigh anomalies can be tuned to achieve narrow extinction peaks originating from the resulting surface lattice resonances generated in our antennas made from highly doped Ge1−xSnx.