Mode-filtering technique based on all-fiber-based external cavity for fiber-based optical frequency comb.

Area of Science:

• Optics and Photonics
• Laser Physics
• Frequency Metrology

Background:

• Optical frequency combs are crucial for high-precision measurements.
• Increasing the repetition rate (f_rep) of fiber-based combs is challenging due to physical limitations.
• Stabilizing the carrier envelope offset frequency (f_ceo) is essential for comb applications.

Purpose of the Study:

• To develop a mode-filtering technique for a high f_rep fiber-based optical frequency comb.
• To achieve a high multiplication factor for f_rep.
• To ensure the stability and robustness of the comb against environmental fluctuations.

Main Methods:

• An all-fiber external cavity was employed for mode filtering.
• A long fiber (6.7 m) was used in a fiber ring cavity to mitigate limitations on shortening cavity length.
• A double-pass configuration was utilized to achieve f_rep multiplication.

Main Results:

• The repetition rate (f_rep) was successfully multiplied by a factor of 11, increasing from 48.7 MHz to 536.0 MHz.
• A side mode suppression ratio of approximately 25 dB was achieved.
• The carrier envelope offset frequency (f_ceo) was detected and stabilized, showing robustness to environmental fluctuations.

Conclusions:

• The developed mode-filtering technique effectively increases the f_rep of fiber-based optical frequency combs.
• The technique enables robust detection and stabilization of f_ceo.
• This advancement is significant for applications requiring high repetition rate frequency combs.