Search

We propose a broadband end-fire antenna for continuous-wave terahertz (THz) photomixing–based devices working in the frequency range of 0.5–1 THz. A compact Vivaldi antenna is presented that does not require any hyper-hemispherical silicon lens to collect and collimate THz radiation unlike the conventionally used broadside antennas. The antenna is tailored to radiate THz into or receive radiation from a dielectric waveguide placed in close vicinity of it. The antenna is fabricated on an indium phosphide (InP) substrate. A silicon (Si) superstrate is used to improve the directionality of the radiated beam. THz power coupled into Si waveguides is measured using two different techniques between 0.1 and 1.15 THz. Firstly, the waveguide is placed in the optical path of a 1550 nm based continuous-wave THz setup with a commercial broadside emitter, focusing optics, and a detector fabricated on the InP substrate with log-periodic broadside antenna. Secondly, the waveguide is placed in direct contact with the designed Vivaldi antenna–based THz receiver and using the commercial broadside emitter as a source. It is observed that the direct coupling technique using the Vivaldi end-fire antenna outperforms the optically coupled approach at frequencies higher than 668 GHz. Efficient THz photoconductive sources and receivers based on the designed compact Vivaldi end-fire antenna will be suitable for launching THz power into on-chip THz circuitry and for compact THz systems.

We present a 2-port terahertz vector network analyzer (VNA) based on four continuous-wave (CW) photomixers and a pair of telecom-wavelength CW lasers. The presented optoelectronic VNA is free-space coupled and can operate continuously from 0.1 THz to 1 THz with a resolution of 2 MHz. We demonstrate two different applications with it: the determination of the material properties of a quartz wafer and the characterization of a terahertz distributed Bragg reflector (DBR).

Photonic Vector Network Analyzers (PVNA) provide a viable solution to the rising demand for efficient, accurate, and affordable characterization instruments for benchmarking terahertz devices and components. This paper compares continuous-wave and pulsed versions of the free space 2-port PVNA and their aptitudes for THz characterization using a distributed Bragg reflector as an application example.