Fabrication of Bi-material MEMS detector arrays for THz imaging

Recently, there has been a significant interest in Terahertz (THz) technology, primarily for its potential applications in detection of concealed objects as well as in medical imaging for non-invasive diagnostics. This region of the spectrum has not been fully utilized due to lack of compact and efficient THz sources and detectors. However, there are several reports recently on real-time THz imaging using uncooled microbolometer camera and quantum cascade laser (QCL) operating as a THz illuminator. The cameras used in these studies are optimized for infrared wavelengths and do not provide optimal sensitivity in the THz spectral range. The fabrication of microbolometer focal plane arrays (FPAs) is relatively complex due to the required monolithic integration of readout electronics with the MEMS pixels. The recent developments in bi-material based infrared FPAs, utilizing optical readout, substantially simplifies the FPA fabrication process by decoupling readout and sensing. In this paper, design and fabrication of a bi-material based FPAs, optimized for the THz wavelengths, as well as design and integration of the readout optical system for real-time imaging will be described.