Electromagnetic Considerations for Pixellated Planar Bolometer Arrays in the Single-Mode Limit

摘要

Filled arrays of planar bolometers are finding astronomical applications at wavelengths as long as several millimeters. In order to minimize detector size while maintaining element number and performance it is common to push these arrays to scales approaching the single-mode limit. Doing so introduces several new challenges that are not experienced with multi-mode far-infrared detectors having similar pixel size. First, diffractive effects by the pixels themselves are no longer insignificant and will ultimately limit the resolution and polarization response of the optical system. Second, it is necessary to re-examine the coupling between the incident radiation and the individual bolometer absorbing elements. The relatively low f-numbers often employed with millimeter wavelength focal planes can make ideal backshort performance and construction problematic. In addition, typical methods for stray light control that rely on multiple reflections in a lossy medium can fail due to physical size constraints. For these applications, we find resonant absorbers and anti-reflection coatings as effective strategies which can be implemented in the available focal plane area to control stray light.