Laser-Excited Phosphor Light Emission Without Fluorescence Saturation
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Solution Overview
Problem
Existing light emitting devices using phosphors with long luminescence lifetimes experience output saturation of fluorescence when excited by high-energy laser beams, limiting the intensity and wavelength selection of emitted light.
Innovation Solution
The device employs a phosphor with a garnet crystal structure, such as (Gd1-xLax)(Ga1-y-zScyCrz)2Ga3O12, activated by Cr3+, which converts high-energy laser beams into near-infrared light efficiently, preventing fluorescence output saturation by ensuring the energy sum of excitation and fluorescence energies is below the host crystal's bandgap energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a phosphor with long luminescence lifetime is used to enhance wavelength selection freedom and afterglow property, then the degree of freedom in wavelength selection and afterglow property are improved, but fluorescence output saturation occurs when excited by high-energy laser beams
Solution Approach 1:
The patent changes the energy parameter relationship by selecting specific excitation and fluorescence wavelengths such that their sum is below the bandgap energy of the host crystal. This parameter optimization prevents fluorescence saturation while maintaining long luminescence lifetime, resolving the contradiction between wavelength selection freedom and fluorescence intensity.
2Illumination intensity
If the energy density of the laser beam is increased to enhance the intensity of emitted light, then the intensity of light emitted by the phosphor increases, but fluorescence output saturation occurs when the energy density exceeds a predetermined value
Solution Approach 1:
The patent optimizes the energy distribution by selecting excitation and fluorescence wavelengths whose sum is below the bandgap energy. This allows high light intensity to be achieved through wavelength selection rather than energy density increase, maintaining high fluorescence output efficiency without saturation.
3Illumination intensity
If a phosphor with short luminescence lifetime is used to prevent fluorescence saturation, then fluorescence output saturation is prevented, but the degree of freedom in wavelength selection and afterglow property are reduced
Solution Approach 1:
The patent changes the approach from modifying luminescence lifetime to optimizing wavelength energy parameters. By selecting excitation and fluorescence wavelengths such that their sum is below the bandgap energy, the patent achieves high fluorescence intensity while maintaining long luminescence lifetime and wavelength selection freedom.
4Illumination intensity
If high light density excitation is applied to phosphors to achieve high intensity emission, then the intensity of emitted light increases, but the phosphor becomes difficult to emit fluorescence with high intensity when it has long luminescence lifetime due to output saturation
Solution Approach 1:
The patent optimizes the energy parameters by selecting specific excitation and fluorescence wavelengths whose sum is below the bandgap energy. This creates a stable emission system that prevents saturation and ensures reliable high-intensity fluorescence emission regardless of luminescence lifetime.
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 high-intensity, near-infrared light emission with reduced fluorescence saturation, suitable for medical applications like fluorescence imaging and photodynamic therapy, and enhances the spectral distribution of emitted light.
Implementation Method 1
a phosphor with a garnet crystal structure, such as (Gd1-xLax)(Ga1-y-zScyCrz)2Ga3O12, activated by Cr3+, which converts high-energy laser beams into near-infrared light efficiently
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~3(b)
AI summary
A light emitting device (1, 1A, 1B, 1C) includes a light source (2) that emits a primary light (6) having a light energy density exceeding 0.5W/mm2, and a first phosphor (4) that absorbs the primary light to convert the primary light into a first wavelength-converted light (7) having a wavelength longer than that of the primary light. The first phosphor includes a compound serving as a host, the compound being a simple oxide including one kind of metal element or a composite oxide including a plurality of different kinds of the simple oxide as an end member. When an energy conversion value at a peak wavelength of the primary light is E1 electron volts and an energy conversion value at a fluorescence peak wavelength of the first wavelength-converted light is E2 electron volts, a bandgap energy of a crystal of the simple oxide is larger than a sum of the E1 electron volts and the E2 electron volts. An electronic device includes the light emitting device. An inspection method uses the light emitting device.