Semiconductor Laser Diode Ridge Waveguide Segmentation
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Solution Overview
Problem
In semiconductor laser diodes with a ridge waveguide structure, optimizing the overlap between the pumped area and the mode area is challenging due to the interdependence of mode guidance and current conduction, which limits the possibilities for efficient device optimization, and varying the ridge dimensions affects operating voltage.
Innovation Solution
The semiconductor laser diode features a ridge waveguide structure with varying widths and materials in different regions, including a superlattice structure in the second region to enhance current spreading, allowing for specific adjustment of mode behavior and current overlap, thereby optimizing laser diode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the ridge width is reduced to improve mode guidance, then the mode area is reduced, but the current spreading area is also reduced leading to increased operating voltage
Solution Approach 1:
The ridge structure is segmented into multiple regions with different widths along the longitudinal direction. The first region has a wider ridge for current spreading, while the second region has a narrower ridge for mode guidance. This segmentation allows independent optimization of current conduction and optical mode confinement without the trade-off present in uniform ridge structures.
Solution Approach 2:
Different regions of the ridge are given different local properties - the first region has larger cross-sectional dimensions optimized for electrical current spreading, while the second region has smaller dimensions optimized for optical mode guidance. This local differentiation resolves the contradiction by allowing each region to perform its specific function optimally.
2Productivity
If the ridge dimensions are changed to optimize the overlap between pumped area and mode area, then the laser efficiency is improved, but the mode behavior and current conduction are both affected limiting optimization possibilities
Solution Approach 1:
By dividing the ridge into functionally distinct segments (first region for current spreading, second region for mode guidance), the invention decouples the interdependence between current conduction and mode behavior. This allows independent optimization of each function to maximize pump-mode overlap and laser efficiency without the constraints of a uniform ridge structure.
Solution Approach 2:
The optimization is extended from a single-dimensional uniform width to a multi-dimensional structure varying along the longitudinal direction. This dimensional expansion provides additional degrees of freedom for optimizing both current spreading and mode confinement simultaneously, thereby improving laser efficiency.
3Manufacturing precision
If the contact area on the ridge is reduced to vary the local current imprint, then the current distribution is improved, but the operating voltage increases
Solution Approach 1:
The contact structure is segmented to provide different contact areas in different regions. The first region has a larger contact area for current spreading, while the second region has a smaller contact area for precise current imprint control. This segmentation allows improved current distribution without the penalty of increased operating voltage that would result from uniformly reducing the contact area.
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 results in semiconductor laser diodes with lower laser thresholds, higher efficiency, and more linear characteristics, while also facilitating better passivation and yield due to slanted edges.
Implementation Method 1
a lateral waveguiding takes place during operation through a refractive index jump between the ridge area and the material adjacent to the ridge
Implementation Method 2
The current injection into the diode, through which the active zone is electrically pumped into inversion, which makes laser operation possible
Implementation Method 3
The optical mode(s) decays exponentially laterally outside the ridge area
Data Source
AI summary
A semiconductor laser diode is disclosed. In an embodiment a semiconductor laser diode includes a semiconductor layer sequence having at least one active layer and a ridge waveguide structure having a ridge extending in a longitudinal direction from a light output surface to a rear side surface and being delimited by ridge side surfaces in a lateral direction perpendicular to a longitudinal direction, wherein the ridge has a first region and a second region adjacent thereto in a vertical direction perpendicular to the longitudinal and lateral directions, wherein the ridge includes a first semiconductor material in the first region and at least one second semiconductor material different from the first semiconductor material in the second region, wherein the ridge has a first width in the first region, and wherein the ridge has a second width in the second region, the second width being larger than the first width.