Abstract
Although standard uncooled infrared (IR) sensors can be used to record information such as the shape, position, and
average radiant intensity of objects, these devices cannot capture color (that is, wavelength) data. Achieving wavelength
selectivity would pave the way for the development of advanced uncooled IR sensors capable of providing color
information as well as multi-color image sensors that would have significant advantages in applications such as fire
detection, gas analysis, hazardous material recognition, and biological analysis. We have previously demonstrated an
uncooled IR sensor incorporating a two-dimensional plasmonic absorber (2D PLA) that exhibits wavelength selectivity
over a wide range in the mid- and long-IR regions. This PLA has a 2D Au-based periodic array of dimples, in which
surface plasmon modes are induced and wavelength-selective absorption occurs. However, the dependence of the
absorption bandwidth on certain structural parameters has yet to be clarified. The bandwidth of such devices is a vital
factor when considering the practical application of these sensors to tasks such as gas detection. In the present study,
control of the bandwidth was theoretically investigated using a rigorous coupled wave analysis approach. It is
demonstrated that the dimple sidewall structure has a significant impact on the bandwidth and can be used to control
both narrow- and broadband absorption. Increasing the sidewall slope was found to decrease the bandwidth due to
suppression of cavity-mode resonance in the depth direction of the dimples. These results will contribute to the
development of high-resolution, wavelength-selective uncooled IR sensors.
