On-chip coherent frequency-domain THz spectroscopy for electrical transport

TL;DR

This paper presents an on-chip coherent frequency-domain THz spectroscopy technique that offers high frequency resolution and the ability to analyze ultrafast electron transport in integrated circuits, surpassing traditional time-domain methods.

Contribution

The authors developed a broadband, high-resolution frequency-domain THz spectroscopy method on a chip, enabling detailed analysis of ultrafast electron transport with simpler setup than femtosecond laser systems.

Findings

Achieved 10 MHz frequency resolution in the 200 MHz to 1.6 THz range.

Enabled identification of multiple reflections using Hilbert analysis.

Demonstrated measurement of ultrafast electron transport in THz circuits.

Abstract

We developed a coherent frequency-domain THz spectroscopic technique on a coplanar waveguide in the ultrabroad frequency range from 200 MHz to 1.6 THz based on continuous wave (CW) laser spectroscopy. Optical beating created by mixing two frequency-tunable CW lasers is focused on photoconductive switches to generate and detect high-frequency current in a THz circuit. In contrast to time-domain spectroscopy, our frequency-domain spectroscopy enables unprecedented frequency resolution of 10 MHz without using complex building blocks of femtosecond laser optics. Furthermore, due to the coherent nature of the photomixing technique, we are able to identify the origin of multiple reflections in the time domain using the Hilbert analysis and inverse Fourier transform. These results demonstrate that the advantages of on-chip coherent frequency-domain spectroscopy, such as its broadband, frequency resolution, usability, and time-domain accessibility, provide a unique capability for measuring ultrafast electron transport in integrated THz circuits.