Light-Diffusing Fiber With High-Index Core and Scattering Centers
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Solution Overview
Problem
Conventional optical fibers face challenges in efficiently coupling with high numerical aperture light sources like LEDs and laser diodes due to mismatches in cross-sectional area and numerical aperture, and increasing the numerical aperture is difficult for light-diffusing fibers with low-index voids that provide scattering efficiency, limiting their flexibility and effectiveness in broad-area illumination applications.
Innovation Solution
A light-diffusing element with a glass core and a polymer or glass cladding, incorporating scattering centers such as dopants, nanoparticles, and internal voids, which increases the numerical aperture and scattering efficiency, allowing for efficient coupling with LEDs and laser diodes while maintaining flexibility, by maximizing refractive index contrast between the core and cladding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the numerical aperture of the fiber is increased to improve coupling efficiency with LEDs and laser diodes, then coupling efficiency is improved, but the flexibility of the fiber deteriorates due to increased diameter requirements
Solution Approach 1:
The patent changes the refractive index parameter of the core material to achieve high numerical aperture without increasing fiber diameter. By using a core with refractive index of 1.7 or higher (such as heavy metal oxide glasses), the numerical aperture can reach 0.65 or higher, enabling efficient coupling with LED and laser diode sources while maintaining standard fiber dimensions and flexibility
Solution Approach 2:
The patent employs composite glass materials containing heavy metal oxides (such as bismuth oxide, lead oxide, or titanium oxide) in the core composition. These composite materials provide both the high refractive index needed for high numerical aperture and the mechanical properties required for fiber flexibility, resolving the contradiction between coupling efficiency and flexibility
2Illumination intensity
If low-index voids are incorporated in the core region to provide scattering efficiency for light diffusing, then scattering efficiency is improved, but the numerical aperture deteriorates due to decreased average refractive index of the core
Solution Approach 1:
The patent fundamentally changes the approach to achieving scattering by using high-refractive-index base glass materials (refractive index 1.7 or higher) in the core. This allows the core to maintain a high average refractive index even when voids are present, because the glass matrix itself has such a high index. The numerical aperture can thus remain high (0.65 or higher) while still achieving effective light scattering for broad-area illumination
Solution Approach 2:
The patent creates local scattering centers within the high-refractive-index core through controlled void formation, dopant distribution, or compositional variations. These local inhomogeneities provide the necessary scattering effect for light diffusing functionality, while the overall high refractive index of the core material maintains the numerical aperture at high levels, resolving the contradiction between scattering efficiency and numerical aperture
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 solution enhances the coupling efficiency to high numerical aperture light sources, improves scattering efficiency, and maintains flexibility, enabling effective broad-area illumination with increased brightness and uniformity.
Implementation Method 1
Radial scattering is typically accomplished by incorporating nanostructural voids in the core region of the fiber. The voids are low-index regions, typically filled with a gas, and have dimensions on the order of the wavelength of the light propagating through the fiber. The refractive index contrast between the voids and surround dense glass matrix effects scattering of the light.
Implementation Method 2
The scattering efficiency, and hence intensity of scattered light, can be controlled by controlling the dimensions, spatial arrangement and number density of voids. The solution enhances the coupling efficiency to high numerical aperture light sources, improves scattering efficiency, and maintains flexibility, enabling effective broad-area illumination with increased brightness and uniformity.
Data Source
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AI summary
A light-diffusing optical element with efficient coupling to light sources with high numerical aperture. The light-diffusing optical element includes a higher index core surrounded by a lower index cladding. The cladding includes scattering centers that scatter evanescent light entering the cladding from the core. The scattered light exits the element to provide broad-area illumination along the element. Scattering centers include dopants, nanoparticles and/or internal voids. The core may also include scattering centers. The core is glass and the cladding may be glass or a polymer. The element features high numerical aperture and high scattering efficiency.