Technological concepts for broad- and narrow-band absorbers in uncooled thermal imagers visualizing MWIR and LWIR

In the field of microbolometer technology, there are two concepts for tuning the absorption to the desired spectral range. Absorbers based on a λ/4 resonator, which is the standard design for commercial uncooled IR imagers, and Plasmonic Metamaterial Absorbers (PMAs). This paper provides an overview of the optical results of both Fraunhofer IMS’s concepts and a comparison between the two technological approaches in terms of their targeted spectral ranges and bandwidths. We show that the quarter-wavelength resonator-based microbolometers provide a broadband absorption spectrum and the PMA-based microbolometers can have a narrow-band absorption spectrum with a bandwidth of about 0.5 μm. In addition, we show how λ/4 absorbers are primarily suited to thermography, while the PMAs can provide a promising platform for gas cameras.