Analytical solutions for the design and evaluation of absorber-coupled waveguide bolometer detectors

Bolometer detectors utilizing superconducting transition-edge sensor thermometers represent the current state-of-the-art for millimeter-wave astrophysical applications. These devices are generally designed using computationally-intensive simulation to predict and optimize electromagnetic performance. The design process therefore requires access to expensive software and does not directly offer physical insight regarding why the detector operates as it does. This paper describes a fast, simple, and insightful analytical technique which applies to the design of absorber-coupled waveguide bolometer detectors operating in the micro- and millimeter-wavelength regimes. We provide simple analytical expressions for the detector input impedance, as well as the resistance and width of the dipole-like absorber, and describe a quick iterative method to determine the appropriate absorber length. The analysis is based upon the EMF Method, which provides a strong theoretical basis for understanding detector operation. We also describe experimental results for an absorber-coupled bolometer detector in circular waveguide.