Polarization self-selection in a coherent beam combination system with an all-optical feedback loop.

Area of Science:

• Optics and Photonics
• Fiber Laser Technology
• Beam Combination

Background:

• Coherent beam combination of fiber amplifiers is crucial for high-power laser systems.
• Achieving stable polarization states in combined beams presents a significant challenge.
• Passive phasing techniques offer a simpler alternative to active control.

Purpose of the Study:

• To demonstrate polarization self-selection in a passive phasing setup for four fiber amplifiers.
• To investigate the role of polarization-maintaining (PM) and non-PM components in the all-optical feedback loop.
• To quantify the improvement in polarization extinction ratio (PER) and interference visibility.

Main Methods:

• Utilized an all-optical feedback loop for passive phasing of four fiber amplifiers.
• Employed a polarization-maintaining (PM) isolator and non-PM components.
• Measured the polarization extinction ratio (PER) and interference pattern visibility of the combined beam.

Main Results:

• Achieved polarization self-selection, increasing the PER of the combined beam.
• Observed a maximum interference visibility of 95.2%.
• Demonstrated a significant increment in PER up to 7.4 dB.
• Found that all PM components are not essential for coherent beam combination with this feedback loop.

Conclusions:

• Passive phasing with an all-optical feedback loop enables effective polarization self-selection in fiber amplifiers.
• Non-PM components are suitable for achieving high output power in such systems.
• This technique simplifies the setup for coherent beam combination, reducing complexity and potentially cost.