Corrugated Substrate Side Surfaces for Optical Device Light Extraction
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Solution Overview
Problem
Existing methods for manufacturing optical devices, such as laser diodes and LEDs, result in a high proportion of light being totally reflected within the substrate due to the rectangular shape of the side surfaces, leading to reduced light extraction efficiency and luminance.
Innovation Solution
The optical device features a substrate with corrugated side surfaces, formed by alternately arranged concave and convex portions, which reduces the incident angle of light and increases the proportion of light that is transmitted rather than reflected, improving light extraction efficiency. This is achieved through a manufacturing method involving the application of a laser beam with a transmission wavelength to form modified layers inside the wafer, which are then used as a division point to create the corrugated shape during the division process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the substrate has a rectangular shape with flat side surfaces perpendicular to the light emitting layer, then the manufacturing process is simple and the device structure is straightforward, but the light extraction efficiency is reduced due to total internal reflection
Solution Approach 1:
The patent applies curvature to the side surfaces of the substrate by forming corrugated structures with alternating concave and convex portions. This curved geometry changes the incident angles of light rays striking the side surfaces, reducing total internal reflection and improving light extraction efficiency without significantly complicating the manufacturing process
Solution Approach 2:
The patent applies local quality by creating corrugated structures only on the side surfaces of the substrate while keeping the front and back surfaces flat. This localized modification targets the specific area where light extraction needs improvement without affecting other parts of the device or requiring complete redesign of the entire substrate
2Loss of energy
If the side surfaces are made corrugated with concave and convex portions to improve light extraction, then the light extraction efficiency increases, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by forming the corrugated structure on the substrate before mounting the light emitting layer. This approach allows the complex geometric structure to be created when the substrate is still accessible and can be processed more easily, rather than attempting to create the same structure after device assembly
3Illumination intensity
If the corrugated structure is formed on the substrate, then the proportion of transmitted light increases and luminance improves, but the manufacturing steps increase
Solution Approach 1:
The patent replaces mechanical machining methods with laser processing to form the corrugated structure. This substitution enables more precise and efficient creation of the complex geometric pattern, improving luminance while minimizing the impact on manufacturing time and productivity
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 corrugated shape of the substrate increases the proportion of light that is transmitted rather than reflected, enhancing light extraction efficiency and improving luminance by allowing more light to be emitted from the device.
Implementation Method 1
applying a pulsed laser beam having an absorption wavelength to the wafer along the division lines to form a laser processed groove along each division line by ablation
Implementation Method 2
the proportion of the light striking each side surface at an incident angle greater than the critical angle is large. As a result, the proportion of the light totally reflected on each side surface is large
Data Source
AI summary
An optical device including a substrate formed of a light transmitting material and a light emitting layer formed on the front surface of the substrate. Both the front surface and the back surface of the substrate are parallel to each other and have substantially the same rectangular shape. The substrate has four side surfaces connecting the front surface and the back surface of the substrate. Each side surface of the substrate has a corrugated sectional shape such that a plurality of concave portions and convex portions are alternately formed.