Study on Mid-Infrared Photon Detector Using Hot Electron Bolometer With Phased Array Antenna

As a high-speed and sensitive mid-infrared (MIR) photon detector, we have studied an MIR superconducting hot electron bolometer (MIR-HEB) with a twin slot-antenna. MIR HEBs have been fabricated; it has been demonstrated that HEBs respond to MIR photons with a response time of a few nanoseconds. However, the effective area of the twin slot-antenna was measured as only approximately 6.3 µm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 66 THz. Therefore, we attempted to expand the area by making it a phased array. The fabricated antenna consists of multiple slot-antennas, MSL circuits, and a load resistor of niobium nitride (NbN) thin film, and the antenna effective areas were evaluated from the absorption rate in the reflection spectrum using an FTIR microscope. The effective area of the antenna consisting of 4 × 4 slot-antennas was estimated to be approximately 48 µm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 66 THz. We also fabricated prototype MIR-HEBs equipped with a phased array antenna and evaluated its dc-characteristics.