Precise measurements of the polarization of the cosmic microwave background (CMB) require detector architectures capable of scaling to large arrays. Thermal kinetic inductance detectors (TKIDs) offer a promising path toward this scaling; however, previous validations have been limited to small prototype chips. Here, we present a comprehensive optical characterization of full arrays of antenna-coupled TKIDs designed for CMB polarimetry at 150 GHz. These arrays are optimized for the expected sky loading of ≈20K. To characterize these resonators under the high optical loads typical of laboratory environments (≈300K), we implemented a “fast chirp” pulsed readout technique. Beyond this specific application, fast chirp readout can be readily applied to extract information from any array of under-coupled resonators with broad resonances. We report system optical efficiencies in excess of 30%, Gaussian antenna beam patterns that match simulations, and spectral bands that fill the targeted 150 GHz atmospheric window with a 25% bandwidth. Furthermore, we constrain the stimulation of absorbers by stray radiation bypassing the antenna to negligible levels. These results validate the optical performance of full-scale TKID arrays, demonstrating their viability for next-generation CMB experiments.
Minutolo et al. (Tue,) studied this question.