A Tightly-Sampled Focal Plane Array in 2nm CMOS with Integrated Direct-Detectors for Terahertz Imaging Applications

The design of a focal plane array (FPA) for imaging at sub-mm wavelengths generally is a trade-off between resolution and sensitivity. For maximum angular resolution, minimal spacing between FPA elements is desired, which leads to increased losses due to spillover and mutual coupling and therefore deteriorates the imaging sensitivity. This work presents the characterization of an ultra-wideband (200 GHz 600 GHz) FPA with integrated direct-detectors, achieving a tight sampling of the focal plane by implementing overlapping of the feed elements, hence alleviating the penalty in aperture efficiency. The overlapping of the feed elements in implemented using a combination of a dual-polarized connected array configuration resembling a chessboard, and leaky-wave propagation in the CMOS stratification. The measured radiation patterns and aperture efficiency show $\lt 1$ dB agreement with simulations. Moreover, a beam spacing corresponding to a near diffraction-limited resolution is combined with a minimum cross-over level below 2 dB over the entire band, making this design a promising candidate for high-resolution terahertz imaging systems. To demonstrate the imaging capabilities of the chessboard array, a quasi-optical imaging setup was developed.