Ceramic Garnet Lighting Device Wavelength Offset
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Solution Overview
Problem
Luminescent light concentrators based on cerium-doped garnets for projectors face efficiency issues when increasing cerium and gadolinium concentrations, leading to lower than expected light conversion efficiency, especially in the red spectral region, due to thermal quenching and Stokes shift losses.
Innovation Solution
A lighting device with a ceramic body doped with specific concentrations of yttrium, gadolinium, and cerium, where the excitation wavelength is offset from the absorption maximum, utilizing a plurality of solid-state light sources to enhance light conversion efficiency and thermal stability, achieving higher red emission with improved spectral distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If cerium and gadolinium concentrations are increased in the garnet ceramic, then red emission intensity is improved, but light conversion efficiency decreases due to thermal quenching and Stokes shift losses
Solution Approach 1:
The patent applies parameter changes by offsetting the excitation wavelength from the absorption maximum (e.g., using 460-470 nm instead of 450 nm for Ce-doped garnets). This wavelength offset creates an optimal balance between achieving sufficient red emission intensity and maintaining high light conversion efficiency by reducing thermal quenching effects while still achieving the desired spectral distribution.
2Use of energy by moving object
If excitation wavelength is tuned to absorption maximum, then light absorption is maximized, but light conversion efficiency decreases due to thermal quenching and Stokes shift losses
Solution Approach 1:
The patent changes the excitation wavelength parameter from the absorption maximum to an offset wavelength (e.g., 10-30 nm offset). This parameter change optimizes the balance between light absorption and conversion efficiency by reducing thermal quenching while maintaining sufficient absorption for practical applications.
3Stability of the object's composition
If gadolinium concentration is increased, then thermal stability is improved, but light conversion efficiency decreases
Solution Approach 1:
The patent optimizes the gadolinium concentration parameter within a specific range (e.g., 10-30 mole %) and combines it with offset excitation wavelength. This coordinated parameter optimization achieves both thermal stability and acceptable light conversion efficiency by balancing the competing effects of thermal quenching suppression and efficient energy conversion.
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 offset excitation and specific doping concentrations significantly increase the light conversion efficiency of the ceramic body, achieving higher red emission while maintaining thermal stability, closer to theoretically estimated values, and providing a good compromise between intensity, efficiency, and spectral distribution.
Implementation Method 1
the elongated ceramic body comprises a ceramic material configured to wavelength convert at least part of the blue light source light into converter light
Implementation Method 2
the efficiency can substantially be increased when the excitation wavelength of the light sources was not tuned to maximum absorption
Data Source
Figure 1A~1B
Figure 1C
Figure 1D
AI summary
The invention provides a lighting device (1) comprising a plurality of solid state light sources (10) and an elongated ceramic body (100) having a first face (141) and a second face (142) defining a length (L) of the elongated ceramic body (100), the elongated ceramic body (100) comprising one or more radiation input faces (111) and a radiation exit window (112), wherein the second face (142) comprises said radiation exit window (112), 5 wherein the plurality of solid state light sources (10) are configured to provide blue light source light (11) to the one or more radiation input faces (111), wherein the blue light source light (11) has an peak maximum (λex1), wherein the elongated ceramic body (100) comprises a ceramic material (120) configured to wavelength convert at least part of the blue light source light (11) into converter light (101), wherein the ceramic material (120) comprises an 10 A3B5O12:Ce 3+ ceramic material, wherein A comprises yttrium (Y) and gadolinium (Gd), and wherein B comprises aluminum (A1), wherein A comprises in the range of 10-50 atom % Gd, and wherein the ceramic material (120) comprises 0.5-3.5 mole % Ce, wherein the ceramic material (120) comprises an absorption spectrum having an absorption peak maximum (λa), wherein the peak maximum (λex1) is unequal to the absorption peak maximum (λa).