A multi-branch, fiber-based frequency comb with millihertz-level relative linewidths using an intra-cavity...

Area of Science:

• * Optics and Photonics
• * Quantum Metrology
• * Laser Physics

Background:

• * Fiber-based frequency combs are crucial for precise frequency measurements.
• * Achieving high frequency stability and linewidth transfer across wavelengths remains a challenge.
• * Multi-branch configurations offer potential for enhanced optical frequency comb systems.

Purpose of the Study:

• * To demonstrate millihertz-level frequency stability transfer using fiber-based frequency combs.
• * To investigate the impact of multi-branch configurations on comb performance.
• * To analyze the sources of frequency noise in branched fiber systems.

Main Methods:

• * Employed fiber-based frequency combs with multi-branch configurations.
• * Utilized an intra-cavity electro-optic modulator for broad servo bandwidth repetition rate control.
• * Stabilized repetition rate frequencies using a stable continuous-wave laser as a common reference.

Main Results:

• * Demonstrated linewidth and frequency stability transfer to another wavelength at the millihertz level.
• * Achieved 99% and 30% energy concentration to the carrier at 1 kHz and 7.6 mHz bandwidths, respectively.
• * Attained frequency instability of 3.7x10⁻¹⁶ at 1 s, improving to 5-8x10⁻¹⁹ at 10000 s.

Conclusions:

• * Multi-branch fiber frequency combs can effectively transfer high frequency stability.
• * The primary source of frequency noise in the out-of-loop beat is phase noise in branched optical fibers.
• * This work advances optical frequency metrology with enhanced stability and precision.