Raman-assisted high-efficiency soliton microcombs in a SiO₂ microsphere.

Area of Science:

• Integrated photonics
• Nonlinear optics
• Materials science

Background:

• Soliton microcombs in high-Q microresonators are crucial for optical clocks, spectroscopy, and telecommunications.
• Conventional pumping methods face challenges with low conversion efficiency, high power thresholds, and parasitic nonlinear effects like stimulated Raman scattering (SRS).
• Parasitic nonlinearities can hinder the generation and stability of soliton states.

Purpose of the Study:

• To achieve high-efficiency soliton microcomb generation with a low power threshold.
• To leverage the synergistic interaction between SRS and four-wave mixing (FWM).
• To explore a novel dual-pump strategy in a SiO2 microsphere.

Main Methods:

• Utilized a high-Q SiO2 microsphere for nonlinear optical interactions.
• Implemented a dual-pump strategy: a primary pump for Raman gain and a secondary pump for soliton formation.
• Investigated the interplay between SRS and FWM for soliton microcomb generation.

Main Results:

• Achieved a 21.8% conversion efficiency from pump laser to soliton state.
• Demonstrated reduced soliton formation threshold compared to conventional methods.
• Showcased robust soliton stabilization through dynamic Raman gain compensation and thermal suppression.

Conclusions:

• The dual-pump strategy effectively exploits synergistic SRS and FWM for efficient soliton microcomb generation.
• This method significantly lowers the power threshold and enhances the stability of soliton states.
• Presents a universal pathway for energy-efficient nonlinear photonics in Raman-active microresonators.