Abstract
Wavelength-selective uncooled infrared (IR) sensors have significant advantages with regard to applications such as fire
detection, gas analysis, hazardous materials recognition, and biological analysis. We have previously demonstrated an
uncooled IR sensor based on a two-dimensional plasmonic absorber (2D PLA) that exhibited wavelength-selective
absorption over a wide range spanning the middle and long-wavelength IR regions. This device had a Au-based 2D
periodic dimple-array structure, in which surface plasmon modes were induced, leading to wavelength-selective
absorption, such that the absorption wavelength was determined by the period of the surface dimples. However, dual-band
operation based on this concept has not yet been investigated, even though the ability to absorb in two different
wavelength bands is extremely important for object recognition. In the present study, a dual-band uncooled IR sensor
was developed using a 2D PLA with asymmetric dimple periods (2-D PLA-AP). To achieve multiband absorption, the
Au-based dimples in this device were fabricated so as to have different periods in the orthogonal x and y directions.
Theoretical calculations predicted asymmetric absorption spectra, attributed to Fano resonance in the 2-D PLA-AP. A
sensor was subsequently fabricated using complementary metal oxide semiconductor and micromachining techniques.
Measurement of the spectral responsivity demonstrated that selective absorption occurred in two different wavelength
bands, determined by the dimple periods in the x and y directions. The results obtained in this study will be applicable to
the development of advanced sensors capable of multiband detection in the IR region.
