Infrasonic performance of a passively stabilized, all-fiber, optical frequency reference

Area of Science:

• Physics
• Astronomy
• Optical Engineering

Background:

• Space-based gravitational wave detectors require highly stable frequency references.
• Optical frequency combs and passive fiber interferometers are candidate technologies.

Purpose of the Study:

• To evaluate the infrasonic performance of a fiber optic laser frequency reference.
• To determine the optimal crossover frequency between different frequency stabilization techniques.
• To assess the suitability of fiber references for future gravitational wave observatories like LISA.

Main Methods:

• Stabilization of an optical frequency comb to a Rubidium atomic reference.
• Interrogation of two passive, all-fiber interferometers using digitally enhanced homodyne interferometry.
• Measurement of relative stability between three independent optical frequency references.

Main Results:

• The optimal crossover frequency between the optical frequency comb and fiber interferometers was found to be 1.5 mHz.
• The passive fiber frequency reference demonstrated superior performance compared to the optical frequency comb at frequencies above 1.5 mHz.
• Fiber interferometers achieved a stability of 20 kHz/Hz at 1.5 mHz, improving to 4 Hz/Hz above 3 Hz.

Conclusions:

• The passive fiber optic frequency reference is a viable and superior alternative to optical frequency combs for infrasonic applications in space-based detectors.
• The characterization provides valuable data on the long-term stability and thermal effects influencing passive fiber references.
• These findings inform the design of future frequency reference architectures for advanced scientific missions.