Frequency comb-to-comb stabilization over a 1.3-km free-space atmospheric optical link.

Area of Science:

• Optics and Photonics
• Frequency Metrology
• Optical Communications

Background:

• Stabilizing optical frequency combs typically requires complex optoelectronic systems with strict environmental controls.
• Frequency comb-to-comb synchronization offers a more efficient alternative by transferring stability from a master to a slave comb.

Purpose of the Study:

• To demonstrate a novel method for remote frequency comb stabilization using a free-space optical link.
• To reduce the complexity and equipment required for high-precision frequency comb synchronization over long distances.

Main Methods:

• Utilized a 1.3 km free-space optical link for coherent transfer of two separate frequency comb lines.
• Implemented feedback control to suppress atmospheric phase noise.
• Transferred the stability of a master frequency comb to a slave comb over the optical link.

Main Results:

• Achieved a transfer stability of 1.7 × 10^-15 at 0.1 s averaging over the free-space optical link.
• Maintained the master comb's stability of 1.2 × 10^-15 at 1.0 s across the slave comb's entire spectrum.
• Demonstrated applications in broadband molecular spectroscopy (6 THz bandwidth) and ultra-stable microwave generation (-80 dBc/Hz at 1 Hz phase noise).

Conclusions:

• Remote frequency comb stabilization via free-space optical links is feasible and highly effective.
• This technique significantly simplifies the requirements for long-distance frequency comb applications.
• Enables advanced applications like ground-to-ground and ground-to-satellite optical frequency dissemination.