Optimized sensitivity and beam pattern of a twin-slot antenna coupled NbN HEB mixer at 1.6THz

摘要

We report on a twin-slot antenna coupled superconducting NbN hot electron bolometer (HEB) mixer designed for 1.6THz. Terahertz (THz) radiation is quasi-optically coupled to the HEB with an uncoated elliptical Si lens. Measured DSBreceiver noise temperatures are 1500 K at 0.85 THz, 1200 K at 1.27 THz, 1100 K at 1.31 THz, 1100 K at 1.4 THz, and1000 K at 1.63 THz. This value at 1.63 THz is reduced to 750 K when the hot/cold loads in vacuum are used. Thefrequency dependence of the noise temperature is consistent with the measured FTS spectral response. The measured farfieldbeam patterns of the lens/antenna combination show nearly collimated beams with the side lobes below -16dB byadding a 40 μm extension to a standard Si elliptical lens design, which is understood by considering a slightly lowerdielectric constant of Si (εsubSi/sub) of 11.4 instead of 11.7. The good performance of such NbN HEB mixers makes it suitablefor future high-resolution spectroscopic astronomical applications.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.