Measurement of microresonator frequency comb coherence by spectral interferometry

Area of Science:

• Photonics and Optics
• Quantum Optics
• Nonlinear Optics

Background:

• Microresonator optical frequency combs are crucial for precise frequency generation.
• Understanding their spectral coherence is vital for advanced applications.
• Existing methods for coherence assessment are limited.

Purpose of the Study:

• To experimentally investigate the spectral coherence of microresonator optical frequency combs.
• To apply a spectral interference method to assess coherence across the comb bandwidth.
• To compare experimental findings with theoretical predictions.

Main Methods:

• Utilized a spectral interference technique, adapted from supercontinuum generation studies.
• Measured the complex degree of first-order coherence across the full bandwidth of two distinct frequency combs.
• Performed numerical simulations to validate experimental observations.

Main Results:

• Observed significantly different coherence characteristics between the two investigated frequency combs.
• Identified dynamical regimes that closely resemble stable and unstable modulation instability regimes.
• Demonstrated excellent agreement between experimental data and numerical simulations.

Conclusions:

• The spectral interference method provides a new technique for assessing optical frequency comb stability.
• Experimental results offer strong validation for prior theoretical analyses of comb dynamics.
• The findings enhance understanding of microresonator comb coherence and stability.