A corrugated planar-Goubau-line termination for terahertz waves

TL;DR

This paper introduces a broadband, impedance-matched load for planar Goubau lines at terahertz frequencies, using an exponentially-tapered corrugated line to absorb energy efficiently and reduce reflections.

Contribution

A novel corrugated line design for broadband terahertz Goubau line loads that simplifies fabrication and achieves low reflections across 0.5-1.1 THz.

Findings

Reflections below -19 dB above 580 GHz

Good agreement between simulations and measurements

Simplified fabrication without auxiliary materials

Abstract

The planar Goubau line is a promising low-loss metal waveguide for terahertz interconnects. To enable advanced system architectures and multi-port measurements based on planar Goubau lines, there is a strong need for broadband impedance-matched loads, which can be used to absorb the energy and minimize standing waves in a system. In this work, we propose a matched load for planar Goubau lines based on an exponentially-tapered corrugated line, gradually increasing conductor losses while maintaining small reflections. The corrugation density is high enough to increase conductor losses without requiring an auxiliary low-conductivity material, simplifying the fabrication process. A 400-$\mu$m long planar Goubau line load was fabricated on a 10-$\mu$m thick silicon substrate suspended in the air. Electromagnetic simulations of the load show excellent agreement with calibrated reflection measurements in the frequency range 0.5 THz - 1.1 THz. Above the cut-off frequency of around 580 GHz, the measured reflections are much less than -19 dB, below the noise floor of the characterization setup.