Tapered Fiber Bundle for Coherent Beam Combining
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Solution Overview
Problem
High power fiber laser amplifiers face challenges in combining beams coherently to achieve a uniform phase over the beam diameter, leading to reduced beam quality and increased complexity due to the need for precise alignment of fiber arrays with bulky free-space optical elements.
Innovation Solution
The use of a tapered fiber bundle, where fiber amplifiers are joined into a single fiber mass with an end cap, allowing for beam combining within the fiber material itself, eliminating the need for precise external alignment and maximizing fill factor by ensuring fiber modes overlap and interfere constructively, thereby enhancing beam quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple fiber laser amplifiers are combined using traditional free-space optical elements, then beam power can be increased, but device complexity and alignment precision requirements increase significantly
Solution Approach 1:
The patent merges multiple fiber amplifiers into a single tapered fiber bundle structure, combining the functions of multiple separate amplifiers into one integrated component. This eliminates the need for separate free-space optical elements and reduces overall device complexity while maintaining power scaling capabilities.
Solution Approach 2:
The tapered fiber bundle serves multiple functions simultaneously: it acts as both the amplification medium and the beam combining structure. This multi-functionality eliminates the need for separate combining optics and reduces the number of components required in the system.
2Power
If traditional fiber array combining methods are used, then beam power can be scaled, but manufacturing precision and alignment tolerance become more difficult to achieve
Solution Approach 1:
The patent combines multiple fiber cores into a single tapered fiber bundle where the cores are permanently fused together. This merging eliminates the need for precise alignment of separate fibers during operation, as the relative positions are fixed during manufacturing and maintained throughout the device lifetime.
Solution Approach 2:
The patent employs a tapered structure where the fiber bundle diameter gradually changes along its length. This parameter change allows for mode field matching and reduces sensitivity to alignment errors, making the system more tolerant to manufacturing variations while maintaining effective beam combining.
3Shape
If fiber modes are made to overlap completely for maximum fill factor, then beam quality improves, but device complexity increases due to precise positioning requirements
Solution Approach 1:
The patent merges multiple fiber modes within the tapered bundle structure, allowing them to overlap and interfere constructively. The tapering process naturally brings the modes into close proximity and enables their fields to overlap, achieving high fill factor and improved beam quality without requiring complex external positioning mechanisms.
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 results in a compact, integrated system with improved beam quality and power scaling capabilities, achieving higher fill factor and beam power within a single fiber aperture, reducing losses and thermal management issues, and enabling focusing to a smaller diffraction-limited spot.
Implementation Method 1
ensuring fiber modes overlap and interfere constructively
Implementation Method 2
a tapered fiber bundle, where fiber amplifiers are joined into a single fiber mass
Implementation Method 3
combined lens and sampling grating
Implementation Method 4
combined lens and sampling grating
Data Source
AI summary
A fiber laser amplifier system including a beam splitter that splits a feedback beam into a plurality of fiber beams where a separate fiber beam is sent to a fiber amplifier for amplifying the fiber beam. A tapered fiber bundle couples the output ends of all of the fiber amplifiers into a combined fiber providing a combined output beam. A beam sampler samples a portion of the output beam from the tapered fiber bundle and provides a sample beam. A single mode fiber receives the sample beam from the beam sampler and provides the feedback beam.