LED Extraction via Inclined Grating and Waveguide Segmentation
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Solution Overview
Problem
Optoelectronic devices with light-emitting diodes face challenges in achieving high extraction efficiency and directivity due to the trapping of electromagnetic radiation, particularly because periodic diffraction gratings alter the directivity of the devices.
Innovation Solution
The design incorporates a single-mode waveguide with a diffraction grating in the optoelectronic device, where the diffraction grating is inclined by more than 10° relative to the direction perpendicular to the surface, and the thickness of the waveguide is carefully controlled to ensure efficient extraction of radiation along a specific direction, enhancing both extraction efficiency and directivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a periodic diffraction grating is formed on the transmission surface to increase extraction efficiency, then more guided modes are extracted, but the directivity of the device is altered and degraded
Solution Approach 1:
The semiconductor layer is divided into two distinct portions: a first portion with larger thickness that maintains directivity by preserving the direct radiation mode, and a second portion with smaller thickness that extracts guided modes through the diffraction grating. This segmentation allows each portion to perform its specific function without interfering with the other, resolving the contradiction between extraction efficiency and directivity
Solution Approach 2:
Different regions of the semiconductor layer are assigned different thicknesses to achieve different optical functions. The first portion has optimized thickness for maintaining direct radiation, while the second portion has optimized thickness for guided mode extraction. This local differentiation enables simultaneous achievement of high extraction efficiency and preserved directivity
2Ease of operation
If the thickness of the semiconductor layer is increased to maintain directivity, then fewer guided modes are extracted, but extraction efficiency decreases
Solution Approach 1:
The semiconductor layer is segmented into two portions with different thicknesses. The first portion has larger thickness to maintain directivity and direct radiation mode, while the second portion has smaller thickness optimized for extracting guided modes through the diffraction grating. This segmentation resolves the trade-off by distributing different thickness requirements to different functional regions
Solution Approach 2:
The solution moves from a single-dimensional thickness parameter to a two-dimensional spatial distribution of thickness. By varying the thickness across different spatial regions (first portion vs. second portion), the patent achieves both directivity and extraction efficiency simultaneously, transforming a scalar optimization problem into a spatial distribution problem
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 increases the extraction efficiency and directivity of the optoelectronic device by ensuring that radiation is emitted along a consistent direction, reducing losses and improving the directional emission of light, as demonstrated by simulations showing a highly directional emission pattern with increased power in the desired cone.
Implementation Method 1
comprising a diffraction grating in the second part capable of extracting the electromagnetic radiation from the second portion
Implementation Method 2
the second portion forming a single-mode waveguide
Implementation Method 3
Optoelectronic device 30 further comprises an opaque portion 44 which is reflective for the radiation emitted by active area 18
Data Source
AI summary
An optoelectronic device including an active area capable of supplying an electromagnetic radiation and sandwiched between first and second semiconductor layers, the first semiconductor layer delimiting a surface and including a first portion in contact with the active area and delimiting a first part of the surface and extending in a second portion delimiting a second part of the surface, the second portion forming a single-mode waveguide, the optoelectronic device including an opaque portion reflective for the electromagnetic radiation covering the first part and including a diffraction grating on the second part capable of extracting the electromagnetic radiation from the second portion.