Double Channel Current Injection for VECSEL Uniformity
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Solution Overview
Problem
Conventional surface emitting lasers, particularly VCSELs, face issues with non-uniform current density distribution leading to current crowding and reduced output power due to high horizontal resistance, which limits aperture size and efficiency.
Innovation Solution
A double-channel current injection structure is implemented, with a first channel injecting current towards the center and a second channel towards the edge of the aperture, using an annular high resistance region and current shielding layers to achieve uniform current distribution and reduce absorption losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single current injection channel is used in conventional VCSELs, then the device structure is simple, but current density becomes non-uniform causing current crowding at the aperture edge
Solution Approach 1:
The current injection structure is segmented into two separate channels: a first current injection channel extending to the central region of the aperture and a second current injection channel extending to the edge of the aperture. This segmentation allows independent current paths that can be optimized for different regions, eliminating the current crowding problem while maintaining structural simplicity.
2Power
If the aperture size is increased to improve output power, then more light can be emitted, but current crowding at the edge becomes more severe
Solution Approach 1:
Different regions of the aperture are provided with different current injection characteristics. The first current injection channel targets the central region with appropriate current density, while the second current injection channel targets the edge region. This local quality approach allows the aperture to be enlarged for higher output power while maintaining uniform current distribution across different zones.
3Loss of energy
If current is injected uniformly across the active layer, then absorption losses are reduced, but the device complexity increases
Solution Approach 1:
The current injection structure is divided into two simple channels with distinct spatial distributions. The first channel injects current toward the center while the second channel injects current toward the edge. This segmentation achieves uniform current distribution across the active layer, reducing absorption losses without requiring complex injection mechanisms.
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 enables high-output power single transverse mode oscillation with a larger active layer aperture, improving efficiency and reducing absorption losses, while simplifying manufacturing processes.
Implementation Method 1
a first current injection channel, which may allow current to be injected toward a central portion of an aperture... and a second current injection channel, which may allow current to be injected toward an edge of the aperture
Implementation Method 2
when current is applied to the active layer 114, light is emitted from the active layer 114 due to the recombination of holes and electrons in the active layer 114
Implementation Method 3
The lower and upper DBR layers 113 and 116 are reflection layers having high reflectivity with respect to the oscillation wavelength of the laser. The light is emitted through the upper DBR layer 116 after being repeatedly reflected between the upper DBR layer 116 and the lower DBR layer 113 and amplified in the active layer 114
Data Source
AI summary
Embodiments provide a vertical external cavity surface emitting laser (VECSEL) that may provide a uniform current density in an active layer using a double current injecting channel. The surface emitting laser device may include a double channel current injection structure for uniformly applying current to an active layer, wherein the double channel current injection structure may include: a first current injection channel, which may allow current to be injected toward a central portion of an aperture, which may be a light beam output region formed in the active layer, and may have a smaller diameter than the aperture: and a second current injection channel, which may allow current to be injected toward an edge of the aperture and may be located around the aperture.