CMOS detector arrays for coherent THz imaging: From point-to-point towards plane-to-plane imaging configurations

We explore the applicability of CMOS field-effect transistors for coherent terahertz imaging. In particular, we discuss two configurations: a point-to-point and a plane-to-plane imaging system. With the latter, a 100×100-pixel camera with an active area of 20×20 mm² has been physically simulated by raster-scanning groups of a few detectors across the image plane. Using detectors with a noise-equivalent power of 43 pW/√Hz, a distributed illumination of 432 μW at 591.4 GHz, and an integration time of 20 ms (for a possible frame rate of 17 fps), images with a dynamic range of about 20 dB and a resolution approaching the diffraction limit are obtained. Imaging examples show the potential of CMOS detectors for a real-time camera. It is demonstrated that heterodyning (i) substantially improves the dynamic range, and (ii) allows sensitive determination of object-induced phase changes, which promises the realization of coherent imaging systems.