Laser Activated Remote Phosphor Low Index Coating
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Solution Overview
Problem
Current Laser Activated Remote Phosphor (LARP) applications suffer from inefficient light emission, with about 50% of light being emitted in undesired directions due to the omni-directional nature of phosphor targets, leading to wasted light and reduced optical efficacy.
Innovation Solution
A dielectric layer with a low index coating is introduced between the phosphor and the substrate, utilizing total internal reflection (TIR) effects to redirect light back into the phosphor, enhancing optical efficacy by reflecting light at high angles and optimizing the dichroic filter's angular distribution, and acting as a heat barrier to improve heat conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a mirror such as a dichroic mirror is positioned to reflect light from the excitation source back in the direction of the phosphor element, then light reflection efficiency is improved, but not all desired light can be reflected depending on the incident angle, resulting in wasted light
Solution Approach 1:
The solution segments the light management function into two distinct components: a dichroic mirror for specular reflection and a diffuse reflector for omnidirectional reflection. The dichroic mirror handles light within its effective angular range, while the diffuse reflector captures and redirects light at all angles, including those that would otherwise be lost. This segmentation allows each component to optimize its specific function, resolving the contradiction between reflection efficiency and angular adaptability.
Solution Approach 2:
The patent employs a composite reflective system combining a dichroic mirror (with wavelength-selective properties) and a diffuse reflector (with angle-independent properties). This composite approach integrates two different reflection mechanisms to achieve both high reflection efficiency for usable light and broad angular acceptance for all emitted light, eliminating the trade-off present in single-component systems.
2Productivity
If a dielectric layer is introduced on the interface between phosphor and substrate to increase optical efficacy, then optical flux is improved, but the layer adds complexity to the device structure
Solution Approach 1:
The dielectric layer is designed to exploit total internal reflection (TIR) at the phosphor-dielectric interface. By carefully selecting the refractive index of the dielectric material, the system creates conditions where light attempting to escape through the interface is automatically reflected back into the phosphor layer. This self-service mechanism requires no additional active components or complex control systems, achieving enhanced optical flux through passive optical design alone, thus minimizing added complexity.
3Temperature
If the dichroic layer is made thinner to improve heat conductivity, then heat dissipation is improved, but the layer may not provide sufficient optical filtering
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary between the phosphor and the dichroic mirror. This dielectric layer serves multiple functions: it creates total internal reflection to enhance light extraction, and it acts as a thermal conduit to improve heat dissipation from the phosphor. By placing the dichroic mirror behind this thermally conductive dielectric layer, the system achieves improved heat management while maintaining the optical filtering function of the dichroic mirror, as the dielectric layer itself is optically transparent at the relevant wavelengths.
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 increases optical flux by 5-6% and allows for a thinner dichroic layer, improving heat conductivity and reducing operation temperatures, thereby enhancing the overall efficacy of the phosphor target.
Implementation Method 1
a low index layer which is generating total internal reflection (TIR) effects
Implementation Method 2
Remote phosphor targets in LARP applications are converting light with short wavelength which is used for the excitation into light with longer wavelength
Implementation Method 3
The dichroic may be optimized to a smaller angular distribution which may provide additional efficacy
Data Source
AI summary
A laser-activated remote phosphor (LARP) target with a first layer having a first index of refraction and a phosphor dispersed within the first layer. A second layer which has a second index of refraction different from the first index of refraction and adjoins the first layer at an interface. The first index of refraction is higher than the second index of refraction such that the interface is configured to at least partially reflect light emitted from the phosphor.