Brillouin laser-driven terahertz oscillator up to 3 THz with femtosecond-level timing jitter

TL;DR

This paper presents a novel Brillouin laser-based terahertz oscillator capable of generating up to 3 THz with femtosecond-level timing jitter, significantly advancing spectral purity and coherence in THz sources.

Contribution

Introduces a dual-wavelength laser design with stimulated Brillouin scattering and optical injection to produce highly coherent THz waves with ultra-low phase noise.

Findings

Achieves phase noise below -100 dBc/Hz at 10 kHz

Generates THz waves from 300 GHz to 3 THz

Timing noise below 10 as/√Hz at 10 kHz

Abstract

The terahertz (THz) frequency range, spanning 0.1 to 10 THz, is a field ripe for innovation with vast, developing potential in areas like wireless communication and molecular spectroscopy. Our work introduces a dual-wavelength laser design that utilizes stimulated Brillouin scattering in an optical fiber cavity to effectively generate two highly coherent optical Stokes waves with differential phase noise inherently mitigated. To guarantee robust operation, the Stokes waves are optically injected into their respective pump lasers, which also serves to greatly improve the resulting coherence. The frequency difference between the two wavelengths is converted into THz waves through a uni-traveling-carrier photodiode. This innovative design facilitates the generation of THz waves with phase noise levels of less than -100 dBc/Hz, translating to timing noise below 10~$\mathrm{as} / \sqrt{\mathrm{Hz}}$ at 10 kHz Fourier frequency, over a carrier frequency range from 300 GHz to 3 THz. This development in phase noise reduction establishes a new benchmark in the spectral purity of tunable THz sources. Such advances are pivotal for applications to move beyond oscillator constraints.