Efficient laser noise reduction method via actively stabilized optical delay line.

Area of Science:

• Photonics
• Laser Physics
• Optical Engineering

Background:

• Fiber lasers are susceptible to frequency noise, limiting their application in sensitive measurements.
• Existing noise reduction methods often struggle with low-frequency noise and environmental disturbances.

Purpose of the Study:

• To demonstrate a novel fiber laser noise reduction method.
• To achieve significant reduction in out-of-loop frequency noise, particularly at low Fourier frequencies.

Main Methods:

• Locking a fiber laser to an actively stabilized optical delay line, specifically a 10 km fiber-based Mach-Zehnder interferometer.
• Utilizing heterodyne signal conversion to shift laser noise to the megahertz range for phase-locked loop (PLL) processing.
• Employing a secondary PLL to compensate for environmentally induced phase noise in the optical fiber spool.

Main Results:

• Achieved frequency noise levels of -30 dBc/Hz at 1 Hz.
• Demonstrated a noise reduction exceeding 90 dB compared to the free-running laser state.
• Efficiently reduced out-of-loop frequency noise, particularly at low Fourier frequencies.

Conclusions:

• The proposed method effectively reduces fiber laser frequency noise.
• The technique offers superior performance in suppressing low-frequency noise and environmental phase fluctuations.
• This advancement is crucial for applications requiring highly stable fiber lasers.