We observe that the modal field distribution of a dielectric slot waveguide closely resembles a magnetic dipole antenna. Such an aperture distribution traditionally demands metals, making it ill-suited to high frequencies due to excessive ohmic loss. By terminating a dielectric slot waveguide with a matched free-space interface, a compact all-dielectric radiating magnetic dipole is realized. In this way, we introduce general-purpose dipole antennas, which have long been a mainstay of RF and microwave ranges, into the realm of light wave photonic integrated circuits. The existence of the desired magnetic dipole aperture distribution is experimentally confirmed in the terahertz range, at ∼275 GHz, and good matching is evident in the ∼−25 dB reflection level. This is the electrically smallest radiator to ever be incorporated into an all-dielectric waveguiding platform.

An ultra-wideband (UWB) interconnect technology using indium phosphide (InP)-based transitions for coupling the output signals from terahertz (THz) photodiodes featuring coplanar waveguide (CPW) outputs to low-loss dielectric rod waveguides (DRWs) is presented. The motivation is to exploit the full bandwidth offered by THz photodiodes without limitations due to standard rectangular waveguide interfaces, e.g., for future high data rate THz communications. Full electromagnetic wave simulations are carried out to optimize the electrical performance of the proposed InP transitions in terms of operational bandwidth and coupling efficiency. The transitions are fabricated on 100-µm-thin InP and integrated with silicon (Si) DRWs. Experimental frequency domain characterizations demonstrate efficient THz signal coupling with a maximum coupling efficiency better than − 2 dB. The measured 3-dB and 6-dB operational bandwidths of 185 GHz and 280 GHz, respectively, prove the multi-octave ultra-wideband features of the developed interconnect technology. The 6-dB operational bandwidth covers all waveguide bands between WR-12 to WR-3, i.e., a frequency range between 60 and 340 GHz. In addition, the multi-octave performances of the fabricated interconnects were successfully exploited in proof-of-concept THz communication experiments. Using intermediate frequency orthogonal frequency division multiplexing (OFDM), THz communications are demonstrated for several frequency bands using the same interconnect. Considering soft-decision forward error correction, error-free transmission with data rates of 24 Gbps at 80 GHz and 8 Gbps at 310 GHz is achieved.

A metallic structure is introduced into the vicinity of a mm-wave dielectric rod waveguide in order to accelerate the propagating mode and effect a phase change. When in close proximity, a maximum phase change of 770° phase change is observed at 77 GHz, and there is less than 5 dB of transmission loss over the range of 73-110 GHz. This indicates promise as a solution for phase shifter in the mm-wave and THz region. The mechanical translation range of the phase shifter is less than 1 mm, making it compatible with very small form-factor piezoelectric precision motors. In this way, we can get can avoid complicated electronic or optoelectronic tuning mechanisms that increase loss, reduce bandwidth, and raise system cost.

This paper presents a novel technique for efficient waveguide coupling between a hollow metallic waveguide and a silicon dielectric rod waveguide in the 75–110 GHz range. The technique uses a short section of dielectric slot waveguide as a quarter-wave matching section to enhance robustness, reliability, compactness and yield for all-silicon terahertz integrated devices and systems, compared to those that employ conventional tapered-spike couplers. The transmission and reflection responses of the quarter-wave matched and tapered dielectric rod waveguides are presented, showing less than 2 dB loss. Reflection below -10 dB is achieved over the 75-110 GHz, reaching the lowest reflection magnitude of -25 dB at 97 GHz. The strong localization of the E-field with quarter-wave matching enables contactless coupling of mm waves, even in cases where there is a small separation.

We demonstrate mm-wave sensing of a sealed volume of bio-liquid via a dielectric waveguide's evanescent fields, which are enhanced by narrowing the guide core in order to reduce field confinement. This is exploited to investigate whether a culture of Gliboblastoma cells effects a measurable change in the composition of a nutrient solution. A small discernible decrease in absorption is observed, indicating potential for future safe and noninvasive mm-wave diagnostic tools

We present a method to control the polarization of guided waves in a mm-wave dielectric rod waveguide. A pair of optical posts is situated on either side of the waveguide, and this markedly raises the cutoff of the undesired mode. The isolation is 20 dB over a frequency span from (55-87) GHz. This can be viewed as a proof-of-concept for reconfigurable, general-purpose polarization control and dispersion engineering in mm-wave and terahertz-range dielectric waveguides.