Multicore Fiber Isotherm Layout for Coherent Beam Combining

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Solution Overview

Problem

Coherent beam combining systems face challenges in maintaining coherence due to group delay mismatches induced by thermal gradients and refractive index variations, which deteriorate recombination efficiency and output pulse duration, particularly in ultra-fast fiber laser systems.

Innovation Solution

A multicore fiber geometry with cores arranged along isotherms and housed in an isotropic cooling environment, such as a cold plate with a groove design, to eliminate thermal gradients and reduce group delay mismatches, combined with passive techniques like stress rods for polarization maintenance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional multicore fiber geometry is used, then the system structure is simple, but thermal gradients cause group delay mismatch and deteriorate recombination efficiency

Engineering Contradiction:

Improverecombination efficiencyVSAvoidfiber geometry complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by strategically positioning stress rods in specific locations within the fiber cross-section and using non-uniform doping concentrations in the cladding region. This asymmetric design creates controlled thermal gradients that compensate for the thermal gradients naturally induced by the pump laser geometry, thereby reducing group delay mismatch and improving recombination efficiency without requiring a completely different fiber structure

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes physical parameters including the doping concentration profile in the cladding, the material composition of stress rods, and the geometric dimensions of the fiber structure. By adjusting these parameters, the thermal conductivity distribution is modified to achieve more uniform temperature profiles across the cores, reducing thermal-induced phase errors while maintaining structural feasibility

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If active phase control mechanisms are used, then phase delay control is improved, but system complexity and cost increase

Engineering Contradiction:

Improvephase delay controlVSAvoidcontrol system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements self-service by designing the fiber structure to automatically compensate for thermal gradients through its inherent asymmetric geometry and stress rod configuration. The structure passively maintains phase coherence without requiring external active control systems, electronic feedback loops, or real-time phase adjustment mechanisms, thereby achieving precise phase delay control while minimizing system complexity

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent extracts the active phase control functionality from the system by replacing electronic feedback control with a passively designed fiber structure. The thermal management and phase stabilization functions are built into the fiber's physical structure itself, eliminating the need for separate active control subsystems and their associated complexity

Inventive Principle:

Principle #2Taking out (Extraction)

3Power

If cores are arranged to maximize power handling, then power scaling is improved, but thermal gradients increase causing group delay mismatch

Engineering Contradiction:

Improvepower handling capabilityVSAvoidthermal gradient

Core Design Contradiction:

PowerVSTemperature

Solution Approach 1:

The patent applies local quality by creating regions of different thermal conductivity within the fiber structure. The cladding region has modified doping concentrations that create locally enhanced thermal conductivity pathways, while the core regions maintain their power handling characteristics. This local differentiation allows heat to be conducted away from high-power cores more effectively, reducing thermal gradients without compromising power scaling capability

Inventive Principle:

Principle #3Local 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 configuration ensures uniform temperature profiles across cores, enhancing phase delay control and improving recombination efficiency and output beam quality in coherent beam combining systems.

Implementation Method 1

an isotropic cooling environment housing the multicore fiber, wherein the isotropic cooling environment includes: a cold plate having a groove shaped to fit the multicore fiber

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

multiple cores that are equidistant from the central axis and arranged in a symmetric pattern with respect to the central axis

Methodology Applied

Scientific EffectThermal gradient elimination: Temperature Gradient

Data Source

PatentUS20250264657A1Multicore fiber geometry and isotropic cooling environment mitigating thermal gradients in coherent beam combining

Publication Date: 2025.08.21 WELLS FARGO BANK NA

AI summary

In some implementations, an optical system comprises a multicore fiber having multiple cores arranged along one or more isotherms and an isotropic cooling environment housing the multicore fiber. In some implementations, the isotropic cooling environment includes a cold plate having a groove shaped to fit the multicore fiber and a structure to enclose the multicore fiber within the groove.