Broadband resonator-waveguide coupling for efficient extraction of octave-spanning microcombs

Area of Science:

• Photonics
• Nonlinear Optics
• Microresonator Devices

Background:

• Octave-spanning frequency combs are generated in Kerr nonlinear microresonators.
• Efficient light extraction is crucial but challenging due to frequency-dependent coupling variations.

Purpose of the Study:

• Investigate a pulley waveguide scheme to enhance microcomb extraction, especially at short wavelengths.
• Improve the efficiency of generating broadband frequency combs.

Main Methods:

• Utilized coupled-mode theory to model pulley coupler performance.
• Compared pulley coupling designs with traditional straight waveguide coupling.
• Performed experimental validation of theoretical predictions.

Main Results:

• Demonstrated improved light extraction at short wavelengths using the pulley scheme.
• Achieved a 20 dB improvement in extraction at short wavelengths compared to straight waveguides.
• Showed good agreement between coupled-mode theory predictions and experimental measurements.

Conclusions:

• The pulley waveguide scheme effectively enhances the extraction of octave-spanning microcombs.
• This approach addresses the challenge of frequency-dependent coupling in microresonator-based frequency combs.
• Offers a pathway to more efficient broadband light generation in photonic devices.