Locking of the Cavity-Soliton Repetition Rate via a Piezo-Stretched Amplifier

Laser cavity-solitons represent a cornerstone in advancing optical frequency comb technologies, offering highly stable and robust pulsed sources [1]. In this work, we emphasize the critical importance of achieving a locked and stable soliton state for metrological applications. Leveraging a nested-cavity configuration, where a nonlinear Kerr microresonator is coupled with an amplifying fibre loop, we demonstrate the ability to actively stabilize the soliton repetition rate [2,3]. Stable soliton states are essential for precision applications in frequency metrology, optical communications, and spectroscopy [1,4,5]. The inherent robustness of these dissipative structures, driven by nonlinear self-locking mechanisms, ensures minimal susceptibility to environmental perturbations [6]. By locking the soliton states, we enable fine control over key parameters, such as the free spectral range (FSR) and comb linewidth, critical for integrating these systems into practical, long-term stable metrological setups [2,3]. Furthermore, the ability to actively lock solitons paves the way for enhanced thermal stability, reduced phase noise, and compatibility with external references, addressing the stringent demands of modern applications [4]. © 2025 IEEE.