Thermally accessible broadband soliton microcombs in silicon carbide enabled by dynamic polarization control

TL;DR

This paper introduces a dynamic polarization control scheme to stabilize and enhance broadband soliton microcombs in silicon carbide microresonators, overcoming thermo-optic instability challenges.

Contribution

It presents a novel thermal compensation method using polarization rotation, enabling reliable soliton access and improved bandwidth and power in microcombs.

Findings

Demonstrated a 108-GHz-FSR single-soliton microcomb spanning 450 nm

Achieved 39% improvement in 20-dB bandwidth

Realized 60% increase in comb power compared to static self-cooling

Abstract

Optical microcombs generated in high-Q microresonators are promising chip-scale light sources for applications ranging from optical communications to spectroscopy and metrology. However, thermo-optic instabilities remain a major obstacle to reliable soliton access. Self-cooling using auxiliary modes can stabilize the intracavity power, yet part of the power is continuously allocated to thermal compensation rather than comb generation, thereby limiting comb power and bandwidth. Here we propose a thermal compensation scheme based on dynamic polarization control. During soliton initiation, a fraction of the pump is coupled to an orthogonally polarized mode to provide self-cooling and ensure reliable soliton access. After soliton formation, polarization rotation and pump tuning transfer this cooling power to the comb-generating mode, enabling efficient single-soliton operation. Using this approach, we experimentally demonstrate a broadband 108-GHz-FSR single-soliton microcomb spanning over 450 nm, together with approximately 39% improvement in the 20-dB bandwidth and 60% increase in comb power relative to the static self-cooling configuration. This dynamic polarization-based thermal compensation enables efficient use of available laser power and provides a practical route to high-performance soliton microcombs in platforms with strong thermo-optic effects.