Beveled Fluorescent Crystal Geometry for Trapped Light Extraction
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Solution Overview
Problem
Current light extraction technologies from fluorescent and scintillator crystals are inefficient, leading to limited luminance and power in applications such as LED-pumped luminescent concentrators, scintillators, and quantum optics, where high sensitivity and energy resolution are crucial.
Innovation Solution
A light emitting device with a solid fluorescent or scintillator crystal featuring beveled vertices or edges, where the normal to the beveled surface is oriented to recycle trapped rays, increasing light extraction efficiency by creating artificial escape cones and minimizing overlap with untrapped rays, thereby enhancing the luminance and power of the exit beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a parallelepiped crystal geometry is used, then the manufacturing is simple and robust, but the light extraction efficiency is limited due to total internal reflection trapping most rays
Solution Approach 1:
The patent applies asymmetry by beveling specific vertices or edges of the crystal while maintaining the overall parallelepiped geometry. This creates asymmetric exit surfaces at strategic locations that allow trapped rays to escape without requiring a complete change in crystal shape. The beveled surfaces have different orientations from the main crystal faces, breaking the symmetry that causes total internal reflection.
Solution Approach 2:
The invention adds a new dimensional element by introducing beveled surfaces at vertices or edges, which creates additional exit pathways in directions not available from the standard parallelepiped faces. This allows rays that would otherwise be trapped in three-dimensional total internal reflection to find escape routes through the newly created angular surfaces.
2Loss of energy
If mirrors are placed on crystal faces to reflect trapped rays, then light extraction efficiency improves slightly, but the overall efficiency remains limited to at most 16% in Ce:YAG and 9% in diamond
Solution Approach 1:
The patent extracts the light extraction function from the crystal faces themselves by creating beveled vertices or edges that serve as dedicated exit pathways. Instead of adding mirrors to reflect light back into the crystal, the invention directly provides extraction surfaces oriented to capture and emit trapped rays, eliminating the need for reflective coatings and associated complexity.
Solution Approach 2:
The beveled surfaces act as intermediary structures between the trapped light field inside the crystal and the external environment. These intermediate surfaces are specifically oriented to receive rays that would otherwise be trapped and transfer them to the outside, serving as a mediator that bridges the gap between the high-index crystal interior and the low-index exterior.
3Use of energy by moving object
If the crystal index is increased to improve light absorption, then the absorption efficiency improves, but the percentage of trapped rays increases to 73% in diamond
Solution Approach 1:
The patent applies local quality by maintaining the high-index material properties throughout the crystal volume for optimal absorption, while locally modifying specific vertices or edges with beveled surfaces to provide extraction pathways. This allows the bulk material to maintain its high absorption efficiency while localized regions provide the necessary light escape routes.
Solution Approach 2:
The invention changes the geometric parameters of specific crystal regions by introducing beveled surfaces with specific angles and orientations. This modifies the local optical parameters (escape cone angles, critical angles) at the beveled surfaces without changing the bulk material properties, thereby enabling light extraction while preserving absorption efficiency.
4Illumination intensity
If LED pumping is used to achieve high luminance, then the luminance can reach 10 to 20 times higher than LED, but the power and luminance are still limited by the extraction efficiency
Solution Approach 1:
The patent applies preliminary action by pre-configuring the crystal geometry with beveled vertices or edges before the light generation process. This pre-established geometric structure creates predetermined escape pathways that are ready to capture and emit photons as they are generated by LED pumping, maximizing the utilization of generated light from the outset rather than attempting to correct extraction issues afterward.
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 beveled design significantly increases light extraction efficiency, potentially up to eight times higher than prior art, by allowing trapped rays to exit the crystal, thereby improving luminance and power of the exit beam, and enhancing energy resolution in scintillators.
Implementation Method 1
a solid fluorescent material or a solid scintillator material adapted to absorb an incident light and then emit a luminescent light in said material
Implementation Method 2
a solid fluorescent material or a solid scintillator material adapted to absorb an incident light and then emit a luminescent light in said material
Implementation Method 3
a portion, called trapped portion, of said luminescent light being trapped by total internal reflections in said material
Data Source
AI summary
A light emitting device including a solid fluorescent material or a solid scintillator material adapted to absorb an incident light and then emit a luminescent light in the material, a portion, called trapped portion, of the luminescent light being trapped by total internal reflections in the material, the material including two parallel faces, called large faces, along an horizontal plane xy, and n∈N>2 faces called side faces, and forming vertex between two adjacent side faces and a large face. The material has an invariance of the normals to said side faces by rotation by an angle of 2π/n in said horizontal plan around a z-axis perpendicular to the horizontal plane. The material has a vertex called virtual vertex that is beveled thus forming a surface called beveled vertex, or the material has an edge between two side faces.