Multichannel polarization stabilization for coherently combined fiber laser arrays

Area of Science:

• Optics and Photonics
• Laser Physics
• Fiber Optics

Background:

• Coherent laser combination requires precise control of optical properties.
• Maintaining polarization in non-polarization-maintaining fibers is challenging.
• Existing methods for polarization control can be complex and inefficient.

Purpose of the Study:

• To develop a simplified approach for active polarization control in coherently combined laser architectures.
• To enable closed-loop polarization locking of non-polarization-maintaining fibers.
• To demonstrate compatibility with existing phase control techniques.

Main Methods:

• Utilizing optical phase dithers applied by a phase controller.
• Generating polarization error signals from a single beam sample of the combined output.
• Implementing both hill-climbing and synchronous multidither phase control methods.

Main Results:

• Demonstrated a simplified approach for active polarization control.
• Achieved closed-loop polarization locking of non-polarization-maintaining fibers.
• Showcased compatibility with established phase control techniques.
• Successfully demonstrated simultaneous phase and polarization locking for a five-fiber array.

Conclusions:

• The proposed method offers a simplified and effective solution for polarization control in coherently combined lasers.
• The technique is robust and compatible with various phase control strategies.
• High phasing efficiency (>99%) and polarization extinction ratio (>20 dB) were achieved, validating the approach.