Frequency chirp linearization for ultraflat optical frequency comb generation based on group velocity dispersion

Area of Science:

• Photonics and Optics
• Nonlinear Optics
• Optical Metrology

Background:

• Optical frequency combs (OFCs) are crucial for precision measurement and spectroscopy.
• Generating ultraflat OFCs with high tone counts and minimal power variation remains a challenge.
• Existing methods often involve complex setups or limited flatness.

Purpose of the Study:

• To propose and demonstrate a novel method for generating ultraflat optical frequency combs.
• To enhance the flatness of OFCs generated by cascaded phase and amplitude modulation.
• To investigate the impact of group velocity dispersion on OFC generation.

Main Methods:

• Inserting group velocity dispersion between cascaded phase and amplitude modulation stages.
• Utilizing continuous wave light subjected to phase modulation.
• Simulating the generation of OFCs with the proposed dispersion-engineered method.

Main Results:

• Achieved an ultraflat OFC with 37 tones within 0.88 dB power variation at a modulation index of 20.
• Demonstrated an ultraflat comb generator with 10 GHz frequency spacing.
• Improved the flatness of 15 tones around the center wavelength to 0.98 dB.

Conclusions:

• The proposed method effectively enhances OFC flatness by linearizing chirp.
• Group velocity dispersion is a key parameter for optimizing ultraflat OFC generation.
• This technique offers a promising approach for practical ultraflat OFC sources.