Demonstration of Near Diffraction-Limited Terahertz Images Using a CMOS-Integrated Chessboard Array

This letter demonstrates the near diffraction-limited imaging capabilities of an ultra-broadband terahertz camera based on a tightly sampled chessboard focal plane array (FPA) with integrated direct detectors, operating from 200 to 600 GHz. The terahertz camera is implemented in a 22-nm CMOS process and cointegrated with a hyperhemispherical silicon lens. To provide an efficient illumination of the subject without affecting the resolution of the camera, a quasi-optical imaging system was developed for operation in the WR2.2 band. The imaging system was designed to achieve a dynamic range of 25 dB and an imaging resolution of 2.1 mm at 400 GHz. The crossover level between adjacent beams from the CMOS camera is preserved in the imaging plane and yields 1.4 dB at 400 GHz. Compared with similar works where no mechanical scanning is used for resolution enhancement, the terahertz images created using the chessboard FPA demonstrate the highest resolution up to date.