Kerr Microresonator Soliton Frequency Combs at Cryogenic Temperatures

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Quantum Optics

Background:

• Kerr frequency combs in microresonators are crucial for optical metrology.
• Thermo-refractive noise at room temperature limits the performance of these devices.
• Cryogenic operation offers a potential solution to mitigate noise.

Purpose of the Study:

• To investigate the feasibility and performance of single soliton Kerr frequency combs in silicon nitride microresonators at cryogenic temperatures.
• To assess the impact of cryogenic temperatures on key soliton generation parameters.
• To evaluate the potential for low-noise operation and improved device performance.

Main Methods:

• Experimental investigation of silicon nitride microresonators at temperatures as low as 7 K.
• Adiabatic frequency tuning of the pump laser to access single bright Kerr soliton states.
• Theoretical modeling to support experimental observations and analyze parameter impacts.
• Characterization of thermo-refractive coefficient, quality factor, dispersion, and nonlinearity.

Main Results:

• A two-orders-of-magnitude reduction in the thermo-refractive coefficient was achieved at cryogenic temperatures.
• Single bright Kerr soliton states were easily accessible below 60 K.
• Cryogenic temperatures primarily affected the thermo-refractive coefficient, leaving other soliton generation parameters unaltered.
• Significant potential for improved thermo-refractive noise performance was demonstrated.

Conclusions:

• Cryogenic operation is a viable strategy for enhancing the performance of silicon nitride microresonator-based Kerr frequency combs.
• This approach enables accessible single soliton states and reduced noise, paving the way for advanced chip-scale optical clocks and metrology.
• The findings open new avenues for developing high-precision photonic devices at cryogenic temperatures.