Non-Quadratic GRIN Fiber for Beam Symmetry Homogenization
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Solution Overview
Problem
Optical fibers with a gradient refractive index (GRIN) often maintain asymmetry in the input source, leading to undesirable elliptical or flattened output beam patterns, which is a challenge in optical systems, particularly laser systems.
Innovation Solution
Employing optical fibers with a non-quadratic refractive index profile (RIP) that induces propagation precession, allowing for angular and spatial homogenization of the beam by twisting the fiber during draw, thereby reducing beam asymmetry without significantly sacrificing brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If optical fibers with a gradient refractive index (GRIN) are used to preserve input source brightness, then brightness is maintained, but beam asymmetry is maintained leading to undesirable elliptical output patterns
Solution Approach 1:
The patent applies asymmetry by introducing a controlled asymmetric distortion to the GRIN profile. Specifically, the refractive index profile is modified to include an asymmetric component that counteracts the input beam asymmetry. This is achieved by creating a GRIN fiber where the refractive index varies not only radially but also azimuthally, with the asymmetric variation designed to compensate for the elliptical input pattern and produce a symmetric output beam while maintaining brightness.
2Shape
If a non-quadratic refractive index profile is used to induce propagation precession for angular homogenization, then beam symmetry is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating different refractive index characteristics in different regions of the fiber core. The GRIN profile is designed to have a quadratic component for basic light guidance and an additional asymmetric component for homogenization. This is achieved by controlling the dopant distribution (e.g., germanium dioxide concentration) to vary both radially and azimuthally, with each region having locally optimized properties to contribute to the overall beam symmetrization while maintaining manufacturability through controlled deposition processes.
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
The non-quadratic RIP effectively homogenizes the beam, improving angular and spatial symmetry at the output while maintaining brightness, suitable for various optical systems including materials processing, chemical sensing, and medical applications.
Implementation Method 1
optical fibers having a core with a gradient refractive index (GRIN)
Implementation Method 2
a non-quadratic refractive index profile (RIP) that induces propagation precession, allowing for angular and spatial homogenization of the beam
Data Source
AI summary
Angularly homogenizing gradient index optical fiber having a refractive index profile that is non-quadratic to a degree sufficient to enhance precession of light as it is propagated through the fiber. Deviation from the quadratic may be limited to avoid profoundly changing the radial boundary within the fiber. Beam asymmetry, for example, associated with small aperture sources launched into a fiber off axis, may be made more symmetric as the beam is propagated through the homogenizing gradient index optical fiber. A refractive index profile may be manufactured to avoid a pure quadratic profile, or a fiber having a refractive index profile that is quadratic in only some orientations about the fiber axis may be twisted during draw to induce a refractive index profile path that enhances propagation precession.