Development of Integrated Terahertz Broadband Detectors Utilizing Superconducting Hot-Electron Bolometers
We report on the development of terahertz broadband detectors utilizing superconducting hot-electron bolometers and planar sinuous antennas. In this work, sinuous antennas designed to cover the frequency range of 50 GHz to nearly 900 GHz have been fabricated on semi-insulating silicon substrates. To maintain a self-complementary structure, four antenna arms are used, leading to a frequency-independent input impedance of 74 Omega. Two squares of superconducting niobium HEBs are required at the feed point of the antennas as the sheet resistance of a 10 nm thick niobium thin film is 35 Omega/square. Two sizes of HEBs (120 nm times 240 nm, and 2 mum times 4 mum) have been fabricated using e-beam lithography (EBL), and standard photolithography processes, respectively. A quasi-optical mount with high-resistivity silicon lens has been employed for coupling input power to the sinuous antenna. With a close-cycled cryocooler, the detector performance is studied and evaluated. Detector responsivity at 585 GHz has been presented and compared to waveguide Schottky diode detectors. Noise equivalent power (NEP) measurement is discussed and will be soon performed to the detectors developed in this paper.