Automated co-alignment of coherent fiber laser arrays via active phase-locking

Area of Science:

• Optics and Photonics
• Laser Physics
• Coherent Beam Combining

Background:

• Coherent combining of fiber laser arrays is crucial for high-power laser systems.
• Precise alignment and phase-locking of individual laser beams are significant challenges.
• Existing methods often lack the precision or scalability required for complex arrays.

Purpose of the Study:

• To demonstrate a novel closed-loop approach for high-precision co-alignment of laser beams.
• To achieve simultaneous phase-locking and position-locking in a fiber laser array.
• To enhance the control range and robustness of the alignment system.

Main Methods:

• Development of a closed-loop system utilizing optical transduction of pointing errors into phase errors.
• Implementation of duplicated closed-loop phasing controls to null detected phase errors.
• Application of spatial filtering to the sensed light for extended control range.
• Experimental validation using a five-fiber coherent fiber tip array.

Main Results:

• Simultaneous phase-locking and position-locking of five laser beams achieved with sub-micron accuracy.
• Demonstration of interferometric precision in beam co-alignment.
• Spatial filtering successfully extended the control range beyond single beam diameters.
• Recovery of spatial coherence despite limited far-field beam overlap.

Conclusions:

• The novel closed-loop approach offers a robust and highly precise method for co-aligning laser beams in fiber laser arrays.
• The technique effectively addresses challenges in phase-locking and position-locking, enabling scalable high-power laser systems.
• Spatial filtering proves vital for extending the operational range and maintaining coherence in practical applications.