Laser-Driven White Emitter Using Solid Phosphors

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Solution Overview

Problem

Conventional white light emitters using LEDs suffer from efficiency droop at high power, while laser diodes achieve high optical power density but face issues with powdered phosphor damage in polymer matrices.

Innovation Solution

A high-intensity white light emitting device utilizing a laser diode emitting near-UV or blue light, combined with a single crystal, ceramic, or polycrystalline phosphor that absorbs and converts the light to produce high-intensity white light, with the phosphor being incorporated into or remotely placed from the laser diode packaging, and optionally using reflectors and scattering layers for uniform mixing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If conventional powdered phosphor is used in polymer matrix with laser diode, then high optical power density is achieved, but the phosphor and polymer matrix are damaged due to susceptibility at high power density

Engineering Contradiction:

Improveoptical power densityVSAvoidphosphor durability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent changes the physical state and structural parameters of the phosphor from powdered form in polymer matrix to solid block form (single crystal, ceramic, or polycrystalline). This parameter change enables the phosphor to withstand high optical power densities without damage, resolving the contradiction between achieving high power density and maintaining phosphor durability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures where the phosphor is integrated with the laser diode in a solid-state configuration. The use of solid block phosphors (single crystal, ceramic, or polycrystalline) combined with laser diode creates a composite system that maintains structural integrity and reliability at high optical power densities.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If LED-based white light emitters are operated at high power, then high intensity light is produced, but efficiency droop occurs reducing conversion efficiency

Engineering Contradiction:

Improvelight intensityVSAvoidconversion efficiency

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

The patent replaces the electrical injection mechanism of LEDs with an optical pumping mechanism using laser diodes. This substitution eliminates the efficiency droop phenomenon inherent in LED operation at high currents, allowing high intensity light production while maintaining high conversion efficiency through the laser-diode-to-phosphor optical energy transfer pathway.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Use of energy by moving object

If multiple LEDs are used to preserve efficiency at high power, then conversion efficiency is maintained, but device complexity and number of components increase

Engineering Contradiction:

Improveconversion efficiencyVSAvoidnumber of LEDs

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the efficiency droop problem by replacing the LED light generation mechanism with a laser diode plus solid block phosphor system. This extraction allows single or few laser diodes to replace multiple LEDs, reducing device complexity while maintaining or improving conversion efficiency at high power operation.

Inventive Principle:

Principle #2Taking out (Extraction)

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 device achieves an efficiency of at least 75 lumens per Watt with an intensity of 1100 lumens, maintaining performance without phosphor degradation even after 10 minutes of operation, and offers improved color rendering and safety through the use of resilient phosphor materials.

Implementation Method 1

a laser diode emitting light in a first wavelength range that is converted to light at a longer wavelength by a single crystal, ceramic, or polycrystalline phosphor

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Implementation Method 2

the phosphor absorbs only some of the light emitted from the laser diode

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS10495268B1High intensity solid state white emitter which is laser driven and uses single crystal, ceramic or polycrystalline phosphors

Publication Date: 2019.12.03 RGT UNIV OF CALIFORNIA

AI summary

A white light emitting device includes an edge-emitting laser diode, such as a III-nitride laser diode, emitting light in a first wavelength range that is converted to light at a longer wavelength by a single crystal, ceramic or polycrystalline phosphor, such as a Ce:YAG single crystal phosphor, wherein the phosphor absorbs only some of the light emitted from the laser diode, such that a combination of remaining light emitted from the laser diode with the light at the longer wavelength emitted from the phosphor results in emission of high-intensity white light from the device. Reflectors on either side of the edge-emitting III-nitride laser diode reflect the light from both ends of the edge-emitting laser diode towards the phosphor. One or more sides of the phosphor may roughened, or a scattering layer may be added, to promote uniform color mixing of the emissions.