Terahertz heterodyne spectrometer instruments have been traditionally limited to a single pixel or a handful of pixels due to integration and assembly constraints and a limited availability of local oscillator (LO) power. As a solution we propose a novel silicon-micromachined planar and modular packaging strategy, that will allow for a dense integration of a large number of pixels. Moreover, the RF- and LO signals will be quasi-optically coupled via two identical but opposite lens arrays, such that a single LO-source can efficiently pump all HEB-mixers of the 2x2 pixel demonstrator array simultaneously. This work reports on an intermediate step, where we validate the lens array performance and LO power coupling efficiency, by slightly modifying the silicon package into a transmit array configuration. In this way, the LO power coupled into the stack is directly reradiated on the other side, which is then measured using a liquid helium cooled bolometer.@en

NASA's Planetary Science Decadal Survey has concluded that isotopic measurements of cometary water vapor are a means to unraveling the mysteries involving the origin of Earth's water and the evolution of our solar system. To support this, a recent Jet Propulsion Laboratory internal research program has developed quantum limited superconductor-insulator-superconductor (SIS) receivers in the important 500-600 GHz submillimeter frequency band. These instruments can be used to detect the deuterated water (HDO) ground state (110-101), H216O ortho ground state (110-101), and the oxygen isotopologues H217O and H218O with exquisite sensitivity. To achieve the presented results, we have investigated aluminum oxide (AlOx) and aluminum nitride (AlNx) barrier SIS tunnel junction mixers on the 6-μm silicon-on-insulator substrate. The AlOx and AlNx junction mixer blocks utilize diagonal and smooth-profile conical horns, respectively. In both cases, a commercial 4-8-GHz intermediate frequency low-noise amplifier (LNA) has been integrated into the mixer block. The AlOx (low-current-density) barrier SIS junctions were fabricated with 2-μm gold beam-lead technology, whereas in the case of the AlNx SIS tunnel junction, we use capacitive RF decoupling tabs. The latter approach simplifies fabrication, increases yield, eases the mounting process, and facilitates scaling to higher frequencies. For an actual flight mission, with operation ≤4.2 K, the allowed heat dissipation of the mixer-integrated LNA needs to be minimized. In this article, we also investigate the receiver sensitivity as a function of the LNA dc power consumption. We find that the dc power consumption of the LNA can be reduced to ∼1.6 mW with minimal loss in sensitivity. It is anticipated that the continued InP HEMT development for quantum computer applications are likely to reduce the required LNA power dissipation even further.

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We have demonstrated corrugated horn antennas at 560 GHz fabricated with a deep reactive ion etching (DRIE) process on silicon. The measurement of two of the ( 2 times 2)560 GHz array antenna has shown that the return loss and directivity are 13 dB and 22 dB, respectively. All of the measured antennas had below-25 dB of the cross-polarization and symmetrical beam patterns. The silicon microfabrication technique enables us to build hundreds of horn antennas at once, allowing construction of multi-pixel heterodyne imagers and spectrometers at submillimeter wavelengths.

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We have demonstrated corrugated horn antennas at 340 GHz and 560 GHz fabricated with deep reactive ion etching (DRIE) process on silicon. The measurement of a single 340 GHz antenna showed that the return loss and gain are approximately 25 dB and 21 dBi, respectively. The measurement of two of the 2x2 560 GHz array antenna showed that the return loss and directivity are 13 dB and 22 dB, respectively. All of the measured antennas had below -25 dB of the cross-polarization and symmetrical beam patterns. The silicon microfabrication technique allows fabrication of hundreds of horn antennas at once, allowing construction of multi-pixel heterodyne imagers and spectrometers at submillimeter wavelengths.

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We designed and microfabricated a (2×2) silicon platelet horn antenna at 560 GHz, which is the highest frequency ever among silicon corrugated horn antennas. This was enabled by a silicon compression pin alignment technique of which inaccuracy is less than ± 2 μm in layer-to-layer. The simulation results show that the return loss and gain across the operation frequency of 490-600 GHz are approximately 25 dB and 22 dBi, respectively. The cross-polarization level is below -40 dB. The feature of batch processing will enable us simultaneously to build hundreds or thousands of horn antennas.

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This article presents the latest developments of our work related to a micro-lens antenna integrated in a heterodyne receiver using silicon micromachining technology at Terahertz frequencies. The antenna is composed of a waveguide feed which uses a leaky wave cavity to enhance the directivity and illuminate a shallow lens efficiently. The receiver is a dual-polarized balanced heterodyne detector using hot-electron bolometers (HEB) as mixers. The front-end receiver, including the antenna, can be fabricated using silicon micromachining processes and has seamless integration, which reduces the overall size and losses.@en

This contribution presents the last developments of THz antenna arrays based on silicon micro-machined lenses for heterodyne receivers. The antenna proposed in this manuscript consists of a leaky waveguide feed that illuminates a shallow lens. It achieves high efficiencies and a good coupling to optical systems. Moreover it can be fabricated in parallel using silicon micro-machining techniques, obtaining an array of reduced size and mass to be used for space applications. The current focus of our research is the design of an antenna array operating at 1.9THz based on this antenna for astronomy applications.

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Increasingly, terahertz systems are being used for multi-pixel receivers for different applications from mapping the star-forming regions of galaxies to stand-off radar imaging. Since microstrip patch antennas are too lossy and corrugated horn antenna arrays are difficult to machine at terahertz frequencies, suitable antenna array designs have been one of the key area of research for this field. Moreover, silicon micromachined waveguide housing for front-end integration is becoming very popular for multi-pixel terahertz instruments. This paper describes multi-pixel terahertz instruments with silicon-micromachined front-end and discusses design challenges for integrating terahertz antennas with such systems.

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