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Development of NbN Terahertz IIEB Mixers Coupled Through Slot-Ring Antennas

Authors:
Eyal Gerecht, Dazhen Gu, Xin Zhao, John Nicholson, Fernando Rodriguez-Morales, Sigfrid Yngvesson
Abstract:
In order to improve the power coupling to phonon-cooled hot electron bolometer (PHEB) devices, we are experimenting with a different type of antenna. The development of focal plane arrays (FPAs) with HEB devices requires a new approach for local oscillator (LO) injection. The goal of the project is to eliminate the need for a beam splitter or diplexer and to couple both the LO beam and the signal beam directly to the antenna. This direct coupling can be done by fixing the polarizations of the LO and signal beams to be orthogonal to each other. The slot ring antenna has been used successfully at millimeter-wave frequencies, up to 94 GHz, integrated with Schottky barrier diodes. It can be easily coupled to a dielectric lens since it has a roughly symmetric radiation pattern. Slot-ring antennas are well suited for use with terahertz PHEBs. We have designed, fabricated, and tested the first generation of slot-ring antenna coupled HEB mixers. The slot-ring antenna frequency is centered at 1.6 THz. A coplanar waveguide (CPW) stub filter, which presents an open circuit at the slot-ring, is used. The CPW requires air bridges (well-known in monolithic microwave integrated circuit (MMIC) technology at lower frequencies) in order to ensure that only the main CPW mode can propagate. Although slot-ring antennas have been used successfully at much lower frequencies, they present a challenge at terahertz frequencies. Nevertheless, a preliminary result of noise temperature of 2000 K at 1.6 THz represents the suitability of the slot-ring antenna in future FPAs based on HEB devices.
Categories:
HEB Mixers
Year:
2004
Session:
1
Full-text:
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Page Number(s):
33-40