The development of practical terahertz systems requires high-gain, broadband and robust integrated antennas. In recent years, many photonics-inspired all-dielectric components have been demonstrated, however practical implementation of existing devices usually relies on perforated structures that can be fragile and exhibit cut-offs related to their gratings. In this paper, we present a novel, all-dielectric planar antenna that avoids perforations entirely. The antenna employs a dielectric slab parabolic reflector that collimates incident waves towards radiating rods, producing a fan-shaped beam. A thorough investigation of the optimal guided-wave collimating structure is presented utilizing geometric optics, along with a proof of concept for its use as a beam launcher in integrated terahertz circuits. Thereafter, the device is adapted as an antenna. The novel antenna, 19.83 mm x 20.97 mm in footprint and 200 μm thick, is broadband, low-profile, readily integrable with planar, on-chip components, and exhibits a nearly-flat gain across the 220-330 GHz range, with a maximum value of 21.5 dBi. Input reflection coefficient is below -20 dB across the entire range, indicating excellent 40% fractional bandwidth, and a sidelobe level reaching as low as -28.4 dB for the E-plane and -39.5 dB for the H-plane.

Terahertz waveguide crossings are critical for compact, integrated signal routing in monolithic platforms, but simple waveguide intersections suffer from high losses and crosstalk due to mode mismatch in the regions where the waveguide channels overlap. The Maxwell fisheye lens with its inherent imaging properties is an excellent solution for multichannel intersections, however its circularshape is not easily integrated with common planar input/output waveguides. Here, we introduce all-silicon waveguide crossings basedon Maxwell fisheye lenses reshaped via conformal transformation optics for improved planar waveguide integration in the terahertzrange. Using effective medium techniques with subwavelength air inclusions, we design and fabricate 2 × 2 and 3 × 3 crossings operating over the 220-330 GHz frequency band. The transformed lenses enable aberration-free imaging without mode mismatch, implemented through a single deep reactive ion etching step. Experimental characterization reveals average insertion losses of 1.2 dB andcrosstalk below -50 dB for the fundamental quasi-TE mode, with a 40% bandwidth across the entire 220-330 GHz band, while thequasi-TM mode is also supported for dual-polarization applications. The transformed lenses have a diameter of just 4 mm (3.66λ₀),while the total device footprint including input and output tapers is 11.5 × 11.5 mm². This approach is scalable to N × N waveguidecrossings, providing a broadband and compact solution for low-loss terahertz integrated optics. 

We demonstrate a compact, broadband termination for terahertz dielectric waveguides by coating part of their surfaces with ultrathin single-walled carbon nanotube (SWCNT) films. Using a floating-catalyst chemical vapor deposition process, we fabricated thin SWCNT films with thicknesses ranging from 2 to 53 nm. The SWCNT films were dry-transferred onto high-resistivity dielectric rod waveguides and characterized in 140–220 GHz. Compared to an unloadedrod waveguide (0.7 dB average insertion loss across the band), a 6 mm SWCNT film (2 nm thickness) introduced 3 dB of additional loss across the band, while thicker films (53 nm) introduced up to 47 dB attenuation on average, reaching as high as 70 dB at 150 GHz. Average reflection loss across the band remained above 10 dB for all coatings, with an average of 28.25 dB across the band for the thinnest sample of 2 nm and 27.7 dB for the thickest sample of 53 nm, confirming nearly reflection-free absorption. Shielding efficiency analysis shows that absorption dominated over reflection, yielding total shielding efficiency above 40 dB for thicker films across the whole band. An unprecedented level of 5.5 × 109 dB cm² g⁻¹ for the specific shielding efficiency is achieved, which, to the best ofour knowledge, is the highest reported to date. A perturbative analysis of surface conductivity confirms that ohmic losses are responsible for efficient absorption without altering the waveguide geometry. These results indicate that ultrathin SWCNT films provide a footprint-efficient, broadband, impedance-matched termination for terahertz waveguides, enabling high-density integration of complex on-chip circuits without bulky tapers or radiative terminations.

This article presents novel graphene-based absorber materials which can be directly integrated in terahertz waveguide systems. A simple, low-cost integration method is developed, allowing graphene augmented inorganic nanofibers to be embedded inside a metallic waveguide. In contrast to existing absorbers, the ability to embed such materials in a metallic waveguide allows them to be integrated into complete terahertz systems for large-scale applications. The electromagnetic properties of such materials are then examined using standard network analysis techniques. A wideband measurement setup is developed to enable measurement of a single sample from 67 to 500 GHz, eliminating the need to fabricate multiple samples. The porosity of the integrated material leads to excellent electromagnetic performance across a wide range of frequencies. The samples are found to have a reflection coefficient less than −10 dB for frequencies above200 GHz, while their attenuation per unit length exceeds 35 dB mm⁻¹. The low reflectivity of the material allows it to be used in systems applications where undesired reflections must be avoided. The electromagnetic shielding effectiveness of the material is assessed, with a total effectiveness of 20–45 dB observed for 0.84 mm thick samples.

This article presents the preparation, compositional and electromagnetic characterization of modified few-walled carbon nanotubes/nanofibrillar cellulose (FWCNT/NFC) aerogels integrated in a standard terahertz hollow waveguide and studies their operation as absorbers of electromagnetic waves in the WR-3.4 band (220-330 GHz). Hybrid aerogels consisting of different weight ratios of NFC and modified FWCNT are prepared by freezedrying and characterized through scanning electron microscopy and Raman spectroscopy, and then placed within waveguide cassettes in a simple, low-cost and efficient way that requires no special equipment. A broadband measurement setup is employed for examining the electromagnetic response of the materials. It is found that the materials are excellent absorbers with an average shielding efficiency of 66 dB in the best case and return loss above 10 dB across the band with a flat frequency response. FWCNT aerogels are assessed as a promising candidate for terahertz waveguide terminations.

This article investigates the dichroic properties of aligned γ-Al2O3 nanofibers coated with graphene in the terahertz (THz) regime, revealing significant variance in absorption based on the orientation of the electric field in relation to the nanofibers, arising from the anisotropic nature of the material. Samples are prepared in a hot-wall chemical vapor deposition reactor with varying growth times, resulting in 5 samples with increasing graphene content. Compositional characterization is carried out using scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The samples are characterized electromagnetically using two distinct measurement techniques. First, a novel waveguide measurement setup is deployed, wherein square waveguide cassettes are used to capture the anisotropic behavior of the material and equally measure both polarization states in 67–500 GHz. Then, the samples are characterized using terahertz time-domain spectroscopy up to 4 THz. Both techniques highlight absorption enhancement when the electric field is parallel to the fibers, opening new possibilities for THz devices using polarization filtering.

The development of future 6G communication systems necessitates advanced materials for efficient electromagnetic interference shielding in the sub-terahertz frequency range. This study presents the preparation, porosimetry analysis, compositional and electromagnetic characterization of a highly efficient hierarchically porous carbon-silica composite suitable for shielding and stealth applications in this frequency regime. The composite, fabricated using a mixture of carbon powder and tetraethoxysilane, possesses a highly porous structure with high surface area, which facilitates multiple reflections and scattering of electromagnetic waves. Electromagnetic characterization was conducted using a free-space semi-optical method at 140-220 GHz, focusing on reflection-only measurements due to the sample's large thickness. The results demonstrate that the composite exhibits a qualified bandwidth of 83% over the measured frequency band, with a maximum reflection loss of 35 dB at 187 GHz. Furthermore, measurements demonstrate that electromagnetic power within the sample's volume is effectively attenuated. The composite's shielding efficiency due to reflection is on average 0.26 dB across the band, highlighting its potential for high frequency EMI shielding and stealth applications.