Broadband Terahertz Frequency Comb Based on Actively Mode Locked Resonant Tunneling Diode

TL;DR

This paper presents the first all-electrical, compact terahertz frequency comb source based on a resonant tunneling diode with active mode locking, enabling broadband spectrum generation and potential applications in THz communications.

Contribution

The paper introduces a novel, integrated THz frequency comb generator using a resonant tunneling diode with active mode locking, advancing THz technology capabilities.

Findings

Broadband comb spectrum from 140 to 325 GHz

Wide tuning range of approximately 40 GHz

Successful demonstration as local oscillator in coherent THz transmission

Abstract

The frequency combs characterized by their phase-coherent equidistant spectral modes and precise frequency scales of broadband spectrum, have made them an indispensable part of contemporary physics. A terahertz (THz) frequency comb is a key asset for THz technology applications in spectroscopy, metrology, communications, and sensing. However, the THz frequency comb technologies are comparatively underdeveloped compared to the optical frequency domain, primarily attributed to the deficiency of advanced THz generation components. In this paper, we innovatively demonstrate a compact THz frequency comb source based on a resonant tunneling diode (RTD) through active mode locking technique. By injecting a strong continuous-wave radio frequency (RF) signal via the bias line into a RTD oscillator integrated within a WR-5 hollow metallic waveguide package, we observe a broadband comb spectrum spanning from 140 to 325 GHz. The mode spacing is directly determined by the frequency of the injected RF signal, providing a wide tuning range of approximately 40 GHz. We also employ the proposed frequency comb source as the local oscillator in a coherent transmitter. In particular, this is the first all-electrical compact THz frequency comb source, and the transmission demonstration paves the way to next-generation communication.