Optical Coupling Element Refractive Index for LED Heat Management
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Solution Overview
Problem
Existing light emitting devices face challenges in efficiently coupling light from a light source into a wavelength converter while minimizing light loss and heat dissipation within the luminescent layer, leading to temperature increases and reduced performance.
Innovation Solution
A light emitting device with a wavelength converter and an optical coupling element having a refractive index lower than the converter, allowing for efficient heat transfer and reduced light loss by reflecting a larger portion of light back into the converter, thereby maintaining light intensity and preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If optical contact is made between the light source and the wavelength converter to improve cooling, then heat dissipation is improved, but light loss increases through the optical contact interface
Solution Approach 1:
An optical coupling element with refractive index n1 is introduced as an intermediary between the wavelength converter (refractive index n2) and the surrounding medium. This mediator layer reduces light loss at the interface by optimizing the refractive index transition, while still allowing thermal connection to the heat sink to be maintained through the same or adjacent thermal pathways.
2Loss of energy
If no optical contact is made between the light source and the wavelength converter to reduce light loss, then light efficiency is improved, but heat dissipation worsens leading to temperature increase
Solution Approach 1:
The optical coupling element serves a dual function: optically, it minimizes light loss at the interface by matching refractive indices; thermally, it provides a pathway for heat to conduct from the wavelength converter to the heat sink, resolving the contradiction between light efficiency and heat dissipation.
3Productivity
If the refractive index of the optical coupling element is matched to the wavelength converter to maximize light transmission, then light coupling efficiency is improved, but light reflection losses increase at the exit interface
Solution Approach 1:
The optical coupling element is designed with specific local optical properties (refractive index n1 lower than n2) at the interface with the wavelength converter to optimize light extraction. This local quality difference creates favorable reflection conditions that direct more light toward the desired exit path while minimizing unwanted reflections.
Solution Approach 2:
By deliberately selecting and controlling the refractive index parameter of the optical coupling element to be lower than that of the wavelength converter, the system optimizes the balance between light coupling efficiency and reflection loss reduction, improving overall light extraction performance.
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 enables a higher portion of light to be emitted from the light exit surface while effectively managing heat, ensuring the wavelength converter operates efficiently for a longer period without performance reduction due to temperature issues.
Implementation Method 1
an optical coupling element arranged in contact with the wavelength converter, and in thermal connection with the heat sink
Implementation Method 2
the refractive index of the optical coupling element will determine the portion of light being reflected at the interface between the optical coupling element and the wavelength converter
Implementation Method 3
a wavelength converter which converts light from a blue wavelength range to a yellow wavelength range
Data Source
AI summary
A light emitting device (102, 202) comprising a light source (104) having a light exit surface, a wavelength converter (106) configured to convert light from a first wavelength to a second wavelength, said wavelength converter having a light exit surface (110) and a light entrance surface, a heat sink (100) and an optical coupling element (112), arranged in thermal connection with said heat sink (100) and said wavelength converter (106), wherein said optical coupling element (112) is selected to have a refractive index lower than a refractive index of said wavelength converter (106). The optical coupling element (112) will allow for an efficient heat transfer from the wavelength converter (106) to the heat sink (100) while avoiding loss of light from unwanted surfaces.