Coherent Combining of Fiber Oscillators for High Power Laser Scalability
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Solution Overview
Problem
Current high energy fiber lasers face limitations in power scalability due to small active medium sizes and complex phase locking techniques, which are not robust enough to achieve multi-kilowatt power levels needed for advanced applications.
Innovation Solution
A system that coherently combines the outputs of multiple fiber oscillators using free-space combining nodes with polarizing beam splitters or semi-reflective surfaces, allowing for unequal fiber lengths and incorporating beam shaping optics for flat profile modes, enabling robust phase locking without precise equalization of fiber lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the core diameter of fiber lasers is increased to raise power levels, then power scalability is improved, but the ability to sustain diffraction limited mode of operation deteriorates
Solution Approach 1:
The patent divides a single large-core fiber laser into multiple smaller-core fiber lasers that are coherently combined. Each individual fiber maintains diffraction limited mode operation with a small core diameter, while the coherent combination of multiple fibers achieves the desired high power levels. This segmentation resolves the contradiction by allowing each segment to maintain optical quality while the aggregate system achieves power scalability.
Solution Approach 2:
The patent merges the outputs of multiple individual fiber lasers through coherent combination techniques. By phase-locking multiple fibers and combining their outputs constructively, the system achieves power levels that would be impossible for a single fiber while maintaining beam quality. This merging approach allows the system to overcome the power limitations of individual small-core fibers.
2Reliability
If the Talbot effect is used for phase locking of multiple core fiber lasers, then phase locking is achieved, but the system requires extremely precise equalization of core lengths and positioning in periodical structure
Solution Approach 1:
The patent employs asymmetric coupling schemes where fibers of different lengths and configurations can be combined. Rather than requiring all fibers to be identical and precisely positioned in a periodic structure, the asymmetric approach allows for length mismatches and irregular configurations while still achieving coherent combination through appropriate phase compensation techniques.
Solution Approach 2:
The patent utilizes parameter changes in the coupling and phase control mechanisms to accommodate variations in fiber lengths and positions. By dynamically adjusting phase parameters and coupling conditions, the system can maintain coherent combination even when fibers have different lengths or are not precisely positioned, thereby reducing the stringent alignment requirements of the Talbot effect.
3Manufacturing precision
If active feedback loop with digital wavefront measurement is used, then wavefront control is achieved, but the system becomes too complex for larger numbers of oscillators
Solution Approach 1:
The patent extracts the complex active feedback control system and replaces it with passive coherent combination techniques. By using intrinsic phase-locking mechanisms and passive coupling schemes, the system achieves wavefront control without requiring complex digital measurement and active adjustment systems for each oscillator, thereby simplifying the overall system architecture while maintaining beam quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for scalable high-energy output without the limitations of traditional phase locking methods, enabling the achievement of tens to hundreds of kilowatts of power by ensuring coherent phase locking of individual oscillators, thus overcoming the power scalability issues in fiber lasers.
Implementation Method 1
The node may be implemented with a polarizing beam splitter or a semi-reflective surface
Implementation Method 2
node for coherently combining said first and second beams
Data Source
AI summary
An optical arrangement comprising first and second guided structures for providing first and second beams of electromagnetic energy and a node for coherently combining said first and second beams in free space, that is, with an unguided structure. In the illustrative embodiment, the first and second structures are first and second fiber oscillators. The first and second fiber oscillators may be of unequal lengths. The node may be implemented with a polarizing beam splitter or a semi-reflective surface. Beam shaping optics are included in the node to collimate the first and second beams and provide a flat profile mode thereof. The outputs of plural first and second fiber oscillators are combined via plural nodes to provide a single high energy output beam. Amplifying elements may be disposed between nodes. The plural nodes may be disposed in a single integrated structure along with an outcoupler mirror to coherently phase lock the outputs of the plural oscillators.