Vertical Cavity Light-Emitting Element With Variable Optical Distance
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Solution Overview
Problem
Vertical cavity light-emitting elements, such as surface emitting lasers, face challenges in achieving low threshold voltage and high output with stable slope efficiency.
Innovation Solution
A vertical cavity light-emitting element is designed with a substrate, first and second multilayer reflectors, a semiconductor structure layer including a light-emitting layer, and a light guide layer forming a light guide structure with a center region and a peripheral region, where the second multilayer reflector has a flatness property over both regions, optimizing the optical distance and refractive index to reduce optical loss and enhance light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional vertical cavity light-emitting element is used, then the structure is simple, but the threshold voltage is high and the output is low
Solution Approach 1:
The light guide layer is segmented into a center region and a peripheral region with different optical path lengths. The center region has a longer optical path between reflectors compared to the peripheral region, creating spatial variation in optical properties that enables both low threshold and high output performance
Solution Approach 2:
Different regions of the light guide layer are assigned different optical characteristics. The center region is optimized for light emission with longer optical path, while the peripheral region has shorter optical path to confine and guide light, creating local optimization that resolves the contradiction between threshold and output
2Power
If the optical distance between reflectors is increased to improve light emission, then the output increases, but the optical loss increases
Solution Approach 1:
The patent introduces spatial dimensionality variation in the optical path length by creating different distances between reflectors in different regions (center vs peripheral). This dimensional change allows simultaneous optimization of light emission in the center region while maintaining low loss through shorter paths in the peripheral region
3Productivity
If the light guide structure is added to concentrate light, then the slope efficiency improves, but the device complexity increases
Solution Approach 1:
The light guide layer serves multiple functions simultaneously: it guides light from the active region, confines optical modes, provides current blocking, and creates the desired optical path length variation. This multi-functionality achieves high slope efficiency while minimizing the addition of separate structural components
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 configuration results in a surface emitting laser with a low threshold voltage, high output, and improved slope efficiency by concentrating laser light near the emission center and reducing scattering loss, leading to stable unimodal or multimodal laser light generation.
Implementation Method 1
a light guide layer configured to form a light guide structure including a center region extending in a direction perpendicular to the upper surface of the substrate between the first and second multilayer reflectors and including a light emission center of the light-emitting layer, and a peripheral region provided around the center region and having a smaller optical distance between the first and second multilayer reflectors than that in the center region
Implementation Method 2
a second multilayer reflector formed on the semiconductor structure layer and constituting a resonator together with the first multilayer reflector
Data Source
AI summary
A vertical cavity light-emitting element comprises a substrate, a first multilayer reflector formed on the substrate, a semiconductor structure layer formed on the first multilayer reflector and including a light emitting layer, a second multilayer reflector formed on the semiconductor structure layer and constituting a resonator together with the first multilayer reflector, and a light guide layer configured to form a light guide structure including a center region extending in a direction perpendicular to the upper surface of said substrate between the first and second multilayer reflectors and including a light emission center of the light-emitting layer and a peripheral region provided around the center region and having a smaller optical distance between the first and second multilayer reflectors than that in the center region. The second multilayer reflector has a flatness property over the center region and the peripheral region.