Planar Non-Periodic High-Index Grating for LED Light Extraction
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Solution Overview
Problem
Semiconductor LEDs suffer from poor light-extraction efficiency due to total internal reflection at the semiconductor-air interface and absorption of light within the device, with existing solutions like surface texturing, DBRs, and photonic crystals being complex, costly, and limited in effectiveness.
Innovation Solution
Incorporating a planar non-periodic high-index-contrast grating as a parabolic reflector and collimating lens in the LED package, which can be easily manufactured and integrated, to enhance light extraction efficiency across a broad spectrum by redirecting and collimating light that would otherwise be lost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If surface texturing is used to increase light output, then light extraction efficiency is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the light extraction function from complex surface texturing and implements it through a simple planar grating structure. The grating lines are formed by depositing a high-index material layer patterned with parallel lines, which simplifies the manufacturing process while maintaining effective light extraction through diffraction and interference effects.
Solution Approach 2:
The patent changes the refractive index parameter by using a high-index material (such as silicon nitride or silicon oxide) for the grating lines. This parameter change enables the planar grating to achieve light extraction efficiency comparable to complex surface texturing, while the grating can be easily fabricated using standard semiconductor processing techniques.
2Loss of energy
If a Distributed Bragg Reflector (DBR) is added to reduce light absorption, then light extraction efficiency is improved, but device complexity and fabrication cost increase
Solution Approach 1:
The planar grating structure serves multiple functions simultaneously: it acts as a light extraction element, a beam shaping element, and a wavelength-selective element. This multi-functionality eliminates the need for separate DBR structures, reducing device complexity while maintaining effective light management across a broad spectrum.
Solution Approach 2:
The patent merges the light extraction function with the beam shaping function into a single planar grating structure. The grating lines are configured to both extract light from the semiconductor layer and shape the emitted beam, combining what would traditionally require separate components into one integrated structure.
3Loss of energy
If a photonic crystal is added to diffract wave-guided modes, then light extraction efficiency is improved, but fabrication complexity increases and light bandwidth is limited
Solution Approach 1:
The patent segments the photonic crystal structure into simple parallel lines formed by depositing high-index material. Instead of requiring complex three-dimensional photonic crystal lattices, the invention uses one-dimensional grating lines that are easily fabricated using standard lithography and deposition techniques, while still achieving effective diffraction of wave-guided modes.
Solution Approach 2:
The patent applies local quality by creating regions of high refractive index material only where needed for light extraction. The grating lines are positioned and dimensioned to locally modify the optical field, diffracting wave-guided modes without requiring the complex periodic structure of photonic crystals across the entire device.
4Loss of energy
If multilayer structures with undulating surface and graded refractive index are used, then light extraction is improved, but fabrication complexity and cost increase
Solution Approach 1:
The patent extracts the essential light extraction function from complex multilayer graded-index structures and implements it through a simple planar grating. The grating lines formed by high-index material provide the necessary optical path differences to extract light efficiently, eliminating the need for multiple layers and graded index profiles.
Solution Approach 2:
The patent uses a simple, easily fabricated planar grating structure that can be produced with standard semiconductor processing. This simple structure replaces expensive and complex multilayer graded-index structures, providing cost-effective light extraction without requiring sophisticated fabrication processes.
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 significantly improves LED efficiency by redirecting and collimating light that would be absorbed, resulting in a more cost-effective and efficient light-emitting diode with improved light extraction capabilities.
Implementation Method 1
a planar non-periodic high-index-contrast grating as a parabolic reflector and collimating lens in the LED package, which can be easily manufactured and integrated, to enhance light extraction efficiency across a broad spectrum by redirecting and collimating light that would otherwise be lost
Implementation Method 2
Incorporating a planar non-periodic high-index-contrast grating as a parabolic reflector and collimating lens in the LED package
Implementation Method 3
Semiconductor LEDs suffer from poor light-extraction efficiency due to total internal reflection at the semiconductor-air interface
Data Source
AI summary
A light emitting diode device is described which includes at least one planar non-periodic high-index-contrast grating. The light emitting diode device includes a cavity formed between a reflective optical element and a transmissive optical element. One or both of the optical elements can be a planar non-periodic high-index-contrast grating. The transmissive optical element can be a collimating lens used to collimate incident beams of light while the reflective optical element can be a parabolic reflector used to reflect incident beams of light along a direction opposite to an incidence direction. A light emitter can be disposed within the cavity and can emit beams of light.