Broadband characterization of the spectral responsivity of thermoelectrically-coupled nanoantennas

Thermoelectrically-coupled nanoantennas (TECNAs)—nanoantennas that use the Seebeck effect to detect radiation—are a promising modality for spectrally resolved detection in the infrared. By tailoring the geometry of a nanoantenna coupled to a micro-cavity, their responsivity and spectral selectivity can be carefully designed. However, to date no measurements have directly established the spectral response of these detectors over a large frequency span in the infrared regime, particularly from 2 μm to 20 μm. In this work, we provide a comprehensive analysis of the spectral selectivity of TECNAs operating within the mid- and long-wave infrared (MWIR and LWIR) regions. We engineer arrays of detectors at 5.5 μm, 10.6 μm, and 14 μm, and we verify their selectivity using polarization-dependent Fourier-transform infrared spectroscopy (FTIR). We also show that the response can be tailored using a combination of antenna and cavity design. Our results not only underscore the potential of TECNAs in advancing sensing applications within the MWIR and LWIR domains, but also offer a promising direction for enhancing other detector modalities.