Ceramic Optoceramics for High Luminance Optical Converters
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Solution Overview
Problem
Conventional optical converters face limitations in achieving high luminance due to heat generation from Stokes losses, which leads to temperature-related attenuation and potential material destruction, especially in phosphor-in-silicone converters with low thermal conductivity and limited refractive index variation, resulting in reduced quantum efficiency and increased self-absorption.
Innovation Solution
The use of doped YAG or LuAG ceramic optoceramics with an embedded grain structure as converter materials, which exhibit high scattering and remission without compromising quantum efficiency, allowing for independent adjustment of absorption and scattering properties to achieve high luminance and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If phosphor-in-silicone converter material is used, then the converter can be manufactured with simple process, but the thermal conductivity is low leading to poor heat dissipation and limited maximum operating temperature
Solution Approach 1:
The patent changes the material parameters by transitioning from silicone-based phosphor converters to ceramic optoceramics with different thermal and optical properties. The ceramic material provides higher thermal conductivity and higher refractive index, enabling better heat dissipation and light scattering while maintaining manufacturability through sintering processes.
Solution Approach 2:
The patent uses composite ceramic optoceramic materials containing phosphor particles embedded in a ceramic matrix. This composite structure combines the light-converting properties of phosphors with the high thermal conductivity and mechanical stability of ceramics, resolving the contradiction between ease of manufacture and temperature resistance.
2Ease of manufacture
If phosphor particles are embedded in silicone matrix, then the converter can be easily manufactured, but the refractive index difference is limited reducing light scattering efficiency
Solution Approach 1:
The patent changes the refractive index parameter by using ceramic materials with refractive index of 1.7-2.2, compared to silicone's refractive index of approximately 1.4. This increased refractive index difference enhances light scattering efficiency while the ceramic sintering process maintains manufacturing feasibility.
3Illumination intensity
If higher excitation power is used to increase luminance, then the luminance output increases, but heat generation from Stokes losses increases leading to thermal quenching and material destruction
Solution Approach 1:
The patent converts the harmful heat generated by Stokes losses into a manageable parameter by using ceramic materials with high thermal conductivity. The heat that would otherwise cause thermal quenching and material destruction is efficiently conducted away, allowing higher excitation powers to be used for increased luminance output.
Solution Approach 2:
The patent changes the thermal conductivity parameter of the converter material from low (silicone) to high (ceramic), enabling the system to handle higher heat loads from increased excitation power while maintaining stable operation and high luminance output.
4Device complexity
If converter material is statically applied without heat dissipation structure, then the device complexity is reduced, but the heat dissipation capability is insufficient limiting luminance achievement
Solution Approach 1:
The patent changes the intrinsic thermal conductivity parameter of the converter material itself, using ceramic optoceramics with high thermal conductivity. This eliminates the need for complex external heat dissipation structures while maintaining structural simplicity and achieving effective heat management.
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
This approach enables the achievement of high luminance with a small emission spot and efficient heat dissipation, maintaining high quantum efficiency and thermal conductivity, thereby minimizing heat generation and extending the operational temperature limit, allowing for compact, high-performance optical converters.
Implementation Method 1
Optical conversion always produces heat in the converter, due to so called Stokes losses. The Stokes losses are caused by the difference of photon energies of the excitation light and the emitted light.
Implementation Method 2
Irrespectively from the failing threshold of the relevant converter materials employed, the effect of thermal quenching reduces quantum efficiency.
Implementation Method 3
The use of doped YAG or LuAG ceramic optoceramics with an embedded grain structure as converter materials, which exhibit high scattering and remission without compromising quantum efficiency
Data Source
AI summary
An optical converter for producing colored or white light from blue excitation light is provided. The converter has good scattering properties to be able to produce nearly white light from the scattered blue light components and the scattered, converted yellow light components. The optical converter includes material including one or more of a YAG ceramic, a LuAG ceramic, and a magnesium-aluminum ceramic exhibiting strong scattering.