Internal phase control of coherent fiber laser array without ambiguous phase based on double wavelength detection

Area of Science:

• Optics and Photonics
• Laser Technology

Background:

• High-power fiber lasers are crucial for manufacturing and medical applications.
• Monolithic fiber laser output power is limited by mode instability and nonlinear effects.
• Coherent Beam Combining (CBC) offers a path to higher output power.

Purpose of the Study:

• To propose and validate an all-fiber CBC structure with internal phase detection that overcomes the pi-phase ambiguity inherent in existing methods.
• To enable compact and scalable high-power fiber laser arrays through a novel phase control technique.

Main Methods:

• Development of an all-fiber CBC structure utilizing dual-wavelength detection, incorporating a beacon laser at a different wavelength.
• Establishment of a mathematical model and derivation of a phase-matched condition for the proposed system.
• Simulation of phase control for fiber laser arrays with 7, 19, and 37 beams.

Main Results:

• The proposed dual-wavelength detection method successfully eliminates pi-phase ambiguity in all-fiber CBC systems.
• Simulations demonstrated robust phase control with a control bandwidth exceeding 1 kHz for various array sizes.
• Analysis confirmed that the beacon laser's spectral width can reach tens of nanometers.

Conclusions:

• The novel internal phase control method based on dual-wavelength detection effectively addresses pi-ambiguity in all-fiber CBC.
• The proposed structure shows promise for achieving high-power CBC experimentally with good robustness and scalability.
• This advancement is expected to enhance the capabilities of fiber laser systems in demanding applications.