VCSEL Current Confining Layer Oxidation Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
VCSELs face challenges in achieving a smaller divergence angle, which affects the spot diameter and resolution in optical communication and storage, due to variations in the diameter of the oxidized aperture and the difficulty in controlling the lasing mode.
Innovation Solution
A VCSEL design with a current confining layer comprising a high-Al-composition AlAs layer and a low-Al-composition AlGaAs layer, where the AlGaAs layer is oxidized from the side surface of the mesa, allowing for precise control of the divergence angle by adjusting the Al concentration, thereby optimizing the single-mode operation and reducing the far-field pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diameter of the oxidized aperture is made smaller to obtain single-mode laser light, then the lasing mode is improved, but the divergence angle becomes greater and the diameter of the oxidized aperture becomes difficult to control
Solution Approach 1:
The current confining layer is divided into multiple semiconductor layers with different Al compositions (first layer with higher Al concentration, second layer with lower Al concentration). This segmentation allows different portions of the layer to be oxidized at different rates, enabling precise control of the oxidized aperture diameter while maintaining single-mode operation.
Solution Approach 2:
Different regions of the current confining layer are given different Al compositions to create local quality variations. The first semiconductor layer has higher Al concentration for faster oxidation, while the second layer has lower Al concentration for slower oxidation, allowing precise control of the oxidized aperture dimensions.
2Shape
If the diameter of the oxidized aperture is made greater to reduce divergence angle, then the divergence angle becomes smaller, but the lasing mode may become multi-mode
Solution Approach 1:
The Al composition parameter is varied within the current confining layer to control oxidation characteristics. By adjusting the Al concentration in different layers, the oxidation rate is controlled, enabling precise control of the oxidized aperture diameter to achieve small divergence angle while maintaining single-mode lasing.
3Device complexity
If a single-layer current confining layer is used, then the structure is simpler, but the diameter of the oxidized aperture is difficult to control precisely
Solution Approach 1:
The current confining layer is segmented into multiple semiconductor layers with different Al compositions. This segmentation provides precise control over the oxidation process, allowing accurate control of the oxidized aperture diameter despite the increased structural complexity.
Solution Approach 2:
The current confining layer uses a composite structure of multiple semiconductor layers with different Al compositions. This composite material approach enables precise control of oxidation characteristics and oxidized aperture dimensions that cannot be achieved with a single-layer structure.
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 design enables a smaller divergence angle and far-field pattern, improving the resolution and reducing errors in optical communication and storage applications, while simplifying the control of the VCSEL's optical characteristics.
Implementation Method 1
The first and second semiconductor layers are selectively oxidized from the side surface of the mesa structure
Data Source
AI summary
A VCSEL includes a first conductivity-type first semiconductor mirror layer on a substrate, an active region thereon, a second conductivity-type second semiconductor mirror layer thereon, and a current confining layer in proximity to the active region. A mesa structure is formed such that at least a side surface of the current confining layer is exposed. The current confining layer includes a first semiconductor layer having an Al-composition and a second semiconductor layer having an Al-composition and being formed nearer to the active region than the first semiconductor layer does. Al concentration of the first semiconductor layer is higher than that of the second semiconductor layer. When oscillation wavelength of laser light is λ, optical thickness being sum of the thickness of the first and second semiconductor layers is λ/4. The first and second semiconductor layers are selectively oxidized from the side surface of the mesa structure.