This work presents a chessboard focal plane array (FPA) camera with state-of-the-art thermal and spatial resolution in the 200 600 GHz frequency range. The FPA is implemented in a 130-nm SiGe BiCMOS technology, where each antenna element is loaded with a direct detector based on heterojunction bipolar transistors (HBTs). The antenna and detector architecture, including the vias and biasing network, were optimized to achieve a noise-equivalent power (NEP) suitable for passive THz imaging. Overall, the estimated loss of the FPA is better than 4 dB between 350 and 600 GHz, of which 1.5 dB is due to ohmic losses in the FPA, 1 dB to mutual coupling between detectors, and 0.7 dB to the impedance mismatch between the detector and antenna. A prototype of 24 pixels was manufactured and mounted on the base of a silicon hyperhemispherical lens with an anti-reflection coating. Excellent spatial resolution is achieved through a tight element spacing in the fabricated FPA, which is only half the wavelength in silicon at 350 GHz and therefore consistent with the state-of-the-art. Its responsivity, noise, and radiation patterns were characterized using a quasi-optical measurement setup. The measured radiation patterns are within 1 dB of simulations, demonstrating that the integrated THz camera achieves excellent spatial resolution. Between 330 GHz and 500 GHz, the NEP was measured to be on the order of 10 pW/vHz. When considering the entire operational band, this NEP results in a noise-equivalent temperature difference (NETD) of the camera is 1.6 K for an integration time of 1 s per pixel, which is comparable to the state-of-the-art. While THz detectors with state-of-the-art sensitivity are limited to single-pixel designs, the presented work combines a multi-pixel implementation with competitive sensitivity.

This contribution presents the assessment of RDL technology at sub-terahertz frequencies based on polybenzoxazole (PBO) polymers. A stack of two PBO layers of 10μm thickness with 3 metallization of 5μm copper is being under development. Vias as small as 10μm and a separation of 60μm are being explored. To assess the materials and capabilities of this technology, GCPW, stripline transmission line structures are being assessed, expecting losses in the order of 1.3dB/mm and 2.1dB/mm respectively. Moreover, two resonators have been designed to enhance the accuracy of the characterization.

Radiative near-field links have gained noticeable interests recently for high-data-rate wireless communication. Unlike far-field links, near-field links can have negligible path loss within hundreds of meters for electrically large antennas at high frequencies. In this work, we propose a multi-lens quasi-optical (QO) system for 100-m near-field backhaul communication at H-band. The QO system is designed with compact size (aspect ratio of 1.3:1) and high coupling efficiency of 82%. Moreover, the rotation of an auxiliary lens realizes beam scanning for the link alignment. The scan range is in the order of 1 m with less than 2 dB scanning coupling loss and scanning magnification of 14.5:1.

This contribution presents a silicon-integrated focal plane array (FPA) THz camera that achieves passive-level sensitivity and a densely sampled field-of-view. The FPA chip is designed in a 130nm SiGe BiCMOS technology from IHP and consists of a previously presented chessboard array topology with integrated direct detectors. The detectors are realized using a differential pair of heterojunction bipolar transistors in a common-base configuration biased in deep saturation. A silicon, hyper-hemispherical lens is mounted on the chip as a primary focusing element. The maximum responsivity of the camera is simulated to be 680 V/W at 350GHz, and above half this value between 260GHz and 600GHz. Simulations show that the minimum NEP is on the order of 2pW/√HZ, yielding an NETD of 1K for a 150ms integration time. For characterization and future imaging demonstrations, the camera is mounted in a quasi-optical setup, which refocuses the beams from the silicon lens onto an imaging plane. Measurements performed in this setup demonstrate that the camera achieves a responsivity on the order of 550/W, while also realizing a dense focal plane sampling.

This work presents an electrically-small lens that has been redesigned towards a flat interface. This way, the lens is easier to integrated, compared to an earlier introduced spherical core-shell lens concept. The lens is created from a single dielectric host material by conformally machining holes into the material. In this process, two artificial dielectric layers are created; The first layer is used for anti-reflection purposes, whereas the second is used to convert the spherical interface to a flat interface. The two layers enable the use of holes with lower aspect ratio drilling, compared to classical gradient-index lenses. The lens is designed to operate in the 140-170 GHz bandwidth, and a prototype with height of only 2.2 mm and diameter of 6.6 mm was fabricated and characterize. The prototype is small enough to fit in many integrated circuit packages. The flat lens was compared to a non-flat core lens in terms of pattern quality, return loss and dielectric loss, with only negligible performance degradation.

In this contribution, we describe a reconfigurable surface, designed in 130um SiGe technology, to realize a fully-electronic, planar chopper aiming at passive terahertz imaging applications. This surface consists of subwavelength metallic patches that are interconnected using FET-based varactors. By switching the bias voltage of the varactors between 0V and 1.2V, the reconfigurable surface can switch between a transmissive and opaque state, respectively. The expected transmissivity is simulated to be between 0.2 and 0.9 over a wide frequency band, from 250 GHz to 550 GHz. This chopping solution would enable a high degree of system integration for future passive terahertz cameras.

The exploration of icy body composition in the solar system has often involved spectroscopic measurements of volatiles detected with remote sensing, such measurements portray materials naturally expelled from the surface that enter the exosphere and potentially escape into space. Variations in the ratio of deuterium and hydrogen in these measurements have led to inconclusive hypotheses regarding potential cometary origins of Earth’s ocean water and/or organics. Observational biases regarding unknown previous processing of the observable ejected materials necessitates studies of more dormant, less-processed bodies. Landed missions on comets have brought focus onto the development of small, sensitive instrumentation capable of similar composition measurements of the nascent surface and near-surface materials. We present an evolution of our compact Fourier-transform millimeter-wave cavity spectrometer that is tuned for sensitivity at 80.6 and 183 GHz where HDO and H₂O exhibit resonance features. We discuss both a low-SWaP (size-weight and power) architecture that uses custom microchip transceiver elements as well as a modular configuration using traditional GaAs-based millimeter-wave hardware. New design features for these systems including quartz-based coupling elements, system thermal management, and a separable clocking board are discussed in addition to sensitivity studies and applications in potential mission scenarios.

The continuous advancements in the coverage and sensitivity of terahertz direct-detector imagers places increasing constraints on the test benches needed for characterization. Already, relative differences on the order of a few decibels are observed between simulated and measured performance in the state-of-the-art literature. This contribution elaborates on our experimental strategies to maximize the characterization accuracy and precision of terahertz direct-detection imagers using a broadband, over-the-air measurement procedure. As a demonstration, four elements within a dense detector array were characterized in the WR2.2 band. By optimizing the modulation frequency in the setup for minimal impact of low-frequency noise and interference, a measurement dynamic range up to 30 dB was achieved, including the path loss over 20 cm. The hardware-to-model agreement of the characterized array is below 1 dB between 325 and 450 GHz.

In this paper, we present a quasi-optical power distribution architecture based on the use of an integrated lens antenna that generates a uniform aperture field distribution. By using such distribution in combination with an integrated lens array, an efficient and scalable quasi-optical power distribution can be achieved at THz frequencies. The proposed architecture is based on a leaky-wave waveguide feed that illuminates an elliptical lens with a top-hat distribution. This method can distribute the power from one antenna to a 7-pixel lens array in a hexagonal configuration with a power coupling efficiency of nearly 60%. This scheme could be potentially used for the local oscillator power distribution in heterodyne THz arrays. A prototype at 450-615GHz has been developed and characterized, achieving an aperture efficiency higher than 80%.