Dual-Junction Fiber Laser Diode for Efficient Optical Coupling
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Solution Overview
Problem
Conventional laser diodes face challenges in efficiently coupling light into optical fibers due to astigmatism and high elliptical aspect ratio, requiring numerous components and increasing the likelihood of optical mirror damage, which are costly and time-consuming to manufacture.
Innovation Solution
A dual junction fiber-coupled laser diode design incorporating a tunnel junction between two guiding layers in a single epitaxial structure, allowing for coherent lasing and reduced divergence, thus enabling efficient coupling with fewer optical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single junction laser diodes are used, then the device structure is simple, but the optical power coupling efficiency into fiber is low due to astigmatism and high elliptical aspect ratio
Solution Approach 1:
The laser diode is divided into multiple independent gain regions (first gain region, second gain region, third gain region) separated by tunnel junctions within a single epitaxial structure. Each gain region can be independently controlled and contributes to the overall optical output, enabling improved coupling efficiency through spatial distribution of emission sources while maintaining a unified device structure.
Solution Approach 2:
The patent transitions from a conventional single-planar junction to a multi-layer vertical structure with tunnel junctions stacked between gain regions. This vertical stacking in the third dimension allows multiple emission sources to be integrated within a compact footprint, improving fiber coupling efficiency without proportionally increasing device area or complexity.
2Manufacturing precision
If multiple optical components (lenses, reflectors, prisms) are used for spatial combining, then the optical power coupling into fiber is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
Multiple gain regions and their emission sources are merged into a single integrated epitaxial structure with tunnel junctions. This consolidation replaces the need for separate external optical components (multiple lenses, reflectors, prisms) that would otherwise be required to combine beams from separate laser diodes, thereby improving coupling efficiency while reducing overall device complexity and manufacturing cost.
Solution Approach 2:
The multi-region laser diode structure performs multiple functions within a single device: it generates multiple coherent beams, provides spatial combining internally through the epitaxial structure, and enables efficient fiber coupling. This multi-functionality eliminates the need for separate external optical components that would otherwise be required to achieve the same capabilities.
3Manufacturing precision
If numerous optical components are used for coupling, then the optical power coupling efficiency is improved, but the likelihood of optical mirror damage increases
Solution Approach 1:
By merging multiple gain regions into a single integrated structure with internal spatial combining capabilities, the patent reduces the number of external optical components (especially mirrors and lenses) required for coupling. This consolidation directly lowers the risk of optical mirror damage by eliminating or reducing the number of optical surfaces exposed to high power densities.
4Ease of manufacture
If conventional laser diodes are used, then the manufacturing process is simple, but the component costs and manufacturing time increase due to requiring numerous optical components
Solution Approach 1:
The patent combines multiple gain regions, tunnel junctions, and waveguide structures into a single epitaxial growth process. This integration eliminates the need to manufacture and assemble multiple separate optical components, thereby simplifying the overall manufacturing process and reducing both manufacturing time and cost despite the increased complexity of the laser diode structure itself.
Solution Approach 2:
The patent employs tunnel junctions with specific doping profiles and thickness parameters to enable internal spatial combining and improve coupling efficiency. By optimizing these structural parameters during epitaxial growth, the device achieves high coupling efficiency without requiring additional external optical components, thereby reducing manufacturing complexity and cost.
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 design achieves nearly twice the optical power coupling efficiency with reduced component costs and manufacturing time, improved reliability, and lower risk of optical mirror damage by spreading optical density over a larger area.
Implementation Method 1
A tunnel junction is positioned between the first and second guiding layers, wherein the tunnel junction is formed from two thin, heavily doped layers positioned in contact with one another
Implementation Method 2
A common vertical waveguide is shared by the active layers of the first and second guiding layers, wherein the common vertical waveguide is formed from the first guiding layer in contact with one of the two thin, heavily doped layers and the second guiding layer positioned in contact with another of the two thin, heavily doped layers
Data Source
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AI summary
A laser diode apparatus has a first waveguide layer including a gain region connected in series with a second waveguide layer with a second gain region. A tunnel junction is positioned between the first and second guide layers. A single collimator is positioned in an output path of laser beams emitted from the first and second waveguide layers. The optical beam from the single collimator may be coupled into an optical fiber.