This study investigates the influence of laser parameters on electromagnetic wave attenuation within a silicon waveguide over a wide frequency range of 67–220 GHz using 3-D full-wave simulations. A 10-layer cylindrical model mimicking the energy distribution of a Gaussian laser beam shape is utilized for the analysis. The conductivity of each layer is calculated, and the S-parameters are simulated via CST Studio Suite. Significantly different attenuation levels are observed for different laser wavelengths used in this study. A 980 nm laser resulted in a substantially higher attenuation comparison to a 405 nm laser which had a minimal impact. Furthermore, by increasing the laser intensity, an increase in attenuation is observed. Moreover, the low level of simulated return loss indicates that solid-state plasma absorption dominates the reflections.

This article experimentally demonstrates a frequency-sweeping notch-beam sub-THz radar frontend based on a two-line array antenna featuring computational imaging. Operating within 237.5 GHz and 250 GHz with 12.5 GHz bandwidth, the radar utilizes a 12 λc delay line to achieve frequency-sweeping capabilities. This configuration allows dynamic notch-beam scanning across angular ranges from − 26.5 ∘ to 28 ∘ . The radar frontend is highly compact with a total size of 20 mm× 14.3 mm× 1.2 mm, including the beam-steering network, a magic-tee for creating the 180 ∘ phase shift required for creating the notch-beam, and the antenna array, and is implemented by silicon micromachining. The radar was evaluated with single and dual-target scenarios utilizing and benchmarking different computational imaging algorithms, i.e., matched filter (MF), fast iterative shrinkage-thresholding algorithm (FISTA), and multiple signal classification (MUSIC). It was found that the MUSIC algorithm outperforms MF and FISTA in range and angular resolution in single-target scenes, achieving a range resolution of 7.8 mm and an angular resolution of 15.7 ∘ , with detection errors of less than 6.6 mm and 3.5 ∘ , respectively. Although the MUSIC algorithm maintains reliable range resolution in dual-target scenarios, it performs poorly in providing angular information.

This article experimentally demonstrates a frequency-sweeping notch-beam sub-THz radar frontend based on a two-line array antenna featuring computational imaging. Operating within 237.5 GHz and 250 GHz with 12.5 GHz bandwidth, the radar utilizes a 12 λc delay line to achieve frequency-sweeping capabilities. This configuration allows dynamic notch-beam scanning across angular ranges from − 26.5 ∘ to 28 ∘ . The radar frontend is highly compact with a total size of 20 mm× 14.3 mm× 1.2 mm, including the beam-steering network, a magic-tee for creating the 180 ∘ phase shift required for creating the notch-beam, and the antenna array, and is implemented by silicon micromachining. The radar was evaluated with single and dual-target scenarios utilizing and benchmarking different computational imaging algorithms, i.e., matched filter (MF), fast iterative shrinkage-thresholding algorithm (FISTA), and multiple signal classification (MUSIC). It was found that the MUSIC algorithm outperforms MF and FISTA in range and angular resolution in single-target scenes, achieving a range resolution of 7.8 mm and an angular resolution of 15.7 ∘ , with detection errors of less than 6.6 mm and 3.5 ∘ , respectively. Although the MUSIC algorithm maintains reliable range resolution in dual-target scenarios, it performs poorly in providing angular information.

This paper introduces a silicon-micromachined lens antenna, fabricated for operation in the 500-750 GHz range, featuring an optimized Graded Index Fresnel Zone Planner Lens (FZPL) design. The antenna efficiently radiates a circularly polarized wavefront without the need for additional phase compensation components. Through fabrication, the antenna achieves a high gain of 36 dBi and maintains a -15 dB return loss across the entire waveguide band. Significantly, this all-dielectric lens antenna exhibits minimal loss, ensuring elevated efficiency in Terahertz (THz) communication applications. With its low profile and compact design, this antenna emerges as a promising solution for upcoming wideband THz communication applications. This work not only emphasizes the innovative design but also underscores the practical realization of high-performance antennas with a compact footprint, leveraging silicon micromachining in the THz frequency bands.

This paper introduces a silicon-micromachined lens antenna, fabricated for operation in the 500-750 GHz range, featuring an optimized Graded Index Fresnel Zone Planner Lens (FZPL) design. The antenna efficiently radiates a circularly polarized wavefront without the need for additional phase compensation components. Through fabrication, the antenna achieves a high gain of 36 dBi and maintains a -15 dB return loss across the entire waveguide band. Significantly, this all-dielectric lens antenna exhibits minimal loss, ensuring elevated efficiency in Terahertz (THz) communication applications. With its low profile and compact design, this antenna emerges as a promising solution for upcoming wideband THz communication applications. This work not only emphasizes the innovative design but also underscores the practical realization of high-performance antennas with a compact footprint, leveraging silicon micromachining in the THz frequency bands.

This paper introduces an innovative siliconmicromachined antenna operating in the 500-750 GHz range, based on an optimized elliptical Fresnel Zone Plate Lens (FZPL) design. The antenna radiates a circularly polarized wavefront without additional phase compensation components. With a gain of 25.7 dBi and a 15 dB return loss over the whole waveguide band, this low-profile, compact antenna presents a promising solution for upcoming wideband THz communication applications. This work highlights the potential of silicon micromachining in achieving high-performance antennas with a compact footprint in the THz bands.

This paper introduces an innovative silicon-micromachined, low-profile, high-gain antenna designed for wideband performance in the whole 500-750 GHz waveguide band. The novel antenna concept is based on an elliptical Fresnel Zone planner lens with optimized distribution of the zone dimensions. Furthermore, without requiring any extra phase compensating components, the design ensures circular polarization, which was measured to an axial ratio of better than 2.5 over the whole waveguide band (40% fractional bandwidth). The measured gain ranges from 24.3 to 25.7 dBi, and the return loss is better than 15 dB over the whole 250 GHz band. The 8.25mm×7.62mm large and only 526 μm thick antenna can be directly mounted onto a standard WM-380 waveguide flange. The measured radiation patterns for circular polarization, the gain, the axial ratio, and the return loss are excellently matching the simulated antenna performance. This work shows that all-dielectric antennas at THz frequencies easily outperform metal-based designs due to drastically reduced loss with only -0.85dB average radiation efficiency in the overall frequency band.

This article investigates the impact of antenna dispersion on wideband Terahertz (THz) imaging systems. It is demonstrated that the effective bandwidth is reduced from the nominal system bandwidth, and thus, the expected image resolution cannot be reached when the antenna system has inappropriate frequency dispersion characteristics. Besides a theoretical analysis and simulations, experiments were conducted using antennas with different dispersion characteristics in an ultra-wideband 500–750 GHz imaging setup to assess the impact on achievable resolution. When utilizing low dispersion dielectric-lens antennas, the system successfully detected multiple targets with a radius of 0.6 mm even when positioned at close distance (2 mm in cross-range and 3 mm in range). In contrast to that, when using higher dispersion horn antennas, the resolution of a dual-target scenario was reduced to 3 mm in cross-range and 4 mm in range. Furthermore, it is shown that the target position reconstruction accuracy, as well as the signal-to-clutter ratio (SCR), are also improved by 68% and 2.7 dB, respectively, when using low dispersion antennas in the same setup. This investigation, for the first time, highlights the importance of considering antenna dispersion for accurate image reconstruction, particularly for high-resolution wideband THz imaging systems.

This article presents an unbalanced-fed silicon micromachined dual-port dual-line antenna array. The radiation pattern of the antenna array can be steered in the E -plane by sweeping the frequency and can be switched between a broad and a notched beam by exciting the ports with in-phase or out-of-phase signals. The antenna is designed for and implemented by silicon micromachining. Each single-line subarray consists of #8 antenna apertures in which the field amplitude is tapered in the H-plane, and the phase imbalance of unbalanced power dividers is minimized by integrated delay sections in the feed network. The measured return loss of the antenna is better than 10 dB from 220 to 295 GHz for both input ports (29.1% fractional bandwidth). The antenna prototype is designed for 40° of beam steering in the E -plane (scanning speed of 4°/GHz) by sweeping the frequency from 238 to 248 GHz. The measured sidelobe level of the broad beam in the H-plane is better than 18.5 dB, and the measured depth of the notched beam is better than 22.5 dB in the entire scanning range. In addition to the dual-port dual-line antenna array, a single-line 1 × 8 antenna array is also implemented for reference measurement purposes. The measured return loss of the single-line antenna array is better than 10 dB from 220 to 314 GHz (35.2% fractional bandwidth), and its measured sidelobe level is between 18 and 21.3 dB in the H-plane from 220 to 280 GHz. Besides, the simulation data and the measurement results are in excellent agreement.

The attenuation of electromagnetic waves in a Plasma medium is a complex topic that has attracted the interest of researchers in both fundamental physics and technology. It may be utilized for a variety of applications such as radar cross section reduction, beam steering, etc. In this study, we described a Surface Dielectric Barrier Discharge micro-plasma slab that was positioned in front of a WR62 waveguide to study the interaction properties of electromagnetic waves with plasma. The plasma slab was found to cause a 3-10% attenuation in the S21 parameter, with the amount of attenuation depending on the frequency of the incident wave.