Brillouin photonics engine in the thin-film lithium niobate platform

TL;DR

This paper introduces the use of thin-film lithium niobate as a scalable platform for integrated Brillouin photonics, demonstrating strong SBS gain, a tunable Brillouin laser, and a microwave photonic notch filter.

Contribution

It presents the first implementation of stimulated Brillouin laser and microwave filter in TFLN, combining high SBS gain with integrated photonic functionalities.

Findings

Achieved angle-dependent strong SBS gain in TFLN overcoming propagation loss

Demonstrated the first TFLN-based stimulated Brillouin laser with >20 nm tuning

Created a high-rejection microwave photonic notch filter integrating multiple components

Abstract

Stimulated Brillouin scattering (SBS) is revolutionizing low-noise lasers and microwave photonic systems. However, despite extensive explorations of a low-loss and versatile integrated platform for Brillouin photonic circuits, current options fall short due to limited technological scalability or inadequate SBS gain. Here we introduce the thin-film lithium niobate (TFLN) platform as the go-to choice for integrated Brillouin photonics applications. We report the angle-dependent strong SBS gain in this platform, which can overcome the intrinsic propagation loss. Furthermore, we demonstrate the first stimulated Brillouin laser in TFLN with a tuning range > 20 nm and utilize it to achieve high-purity RF signal generation with an intrinsic linewidth of 9 Hz. Finally, we devise a high-rejection Brillouin-based microwave photonic notch filter, for the first time, integrating an SBS spiral, an on-chip modulator, and a tunable ring all within the same platform. This TFLN-based Brillouin photonics engine uniquely combines the scalability of this platform and the versatility of SBS. Moreover, it bridges SBS with other functionalities in the TFLN platform, unlocking new possibilities for Brillouin-based applications with unparalleled performances.