Semiconductor Laser Oblique End Face Reflection Control
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Solution Overview
Problem
Semiconductor optical devices face challenges in accurately positioning emitting and incident facets due to reflection issues at cleaved end faces, leading to difficulties in coupling with optical fibers and maintaining uniform gaps in arrays, requiring special equipment and processes.
Innovation Solution
The design of semiconductor optical devices with oblique end faces allows independent direction control of incident and emitting beams, reducing reflection and eliminating the need for special alignment equipment by using oblique end faces that are perpendicular to the cleaved end faces, enabling uniform gap maintenance without additional optical components or processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cleaved end face is used as an incident facet or emitting facet, then the device structure is simple and manufacturing is easy, but reflection factor at the end face is high (approximately 30%)
Solution Approach 1:
The patent applies asymmetry by designing the waveguide to be inclined at a specific angle (e.g., 7 degrees) relative to the cleaved end face, rather than being perpendicular. This asymmetric configuration causes reflected light to diverge at angles that prevent coupling back into the waveguide, thereby reducing the reflection factor while maintaining the simplicity of using a cleaved end face.
Solution Approach 2:
Instead of trying to reduce reflection by making the end face perpendicular to the waveguide (the conventional approach), the patent inverts the approach by intentionally inclining the waveguide relative to the cleaved end face. This inversion of the geometric relationship achieves reflection reduction without requiring complex anti-reflection coatings or specialized end face processing.
2Object-generated harmful factors
If the waveguide is inclined to reduce reflection factor, then reflection is reduced, but the emitting beam direction becomes oblique requiring special alignment equipment and processes
Solution Approach 1:
The patent makes the cleaved end face serve multiple functions: it acts as both the incident facet and the emitting facet for the waveguide, while also serving as the reference surface for coupling with optical fibers. By designing the waveguide inclination relative to this universal reference surface, the patent eliminates the need for separate alignment equipment while maintaining low reflection.
Solution Approach 2:
The cleaved end face itself provides the alignment reference function without requiring external markers or special equipment. The inclined waveguide geometry automatically ensures that the emitting beam exits at an angle that can be directly coupled to optical fibers positioned relative to the cleaved end face, making the system self-aligning.
3Object-generated harmful factors
If oblique end face is used to reduce reflection, then reflection factor is reduced, but maintaining uniform gaps in arrays of semiconductor optical devices becomes difficult
Solution Approach 1:
The patent establishes the cleaved end face as a common reference plane (equipotential surface) for all semiconductor optical devices in an array. By inclining all waveguides at the same angle relative to this common reference, the emitting beams from all devices exit at consistent angles, enabling uniform gap maintenance across the array without requiring individual alignment adjustments.
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 enhances beam direction control, reduces reflection, and simplifies the alignment process, improving coupling efficiency with optical fibers and maintaining uniform gaps in arrays of semiconductor optical devices.
Implementation Method 1
a reflection factor at such the end face on the waveguide is determined due to each index of refractions of a semiconductor and an external ambient atmosphere... it becomes difficult for a reflected light to couple again with the waveguide 101 that is reflected at such the cleaved end face (obliquely cleaved end face)
Implementation Method 2
such the emitting beam 103 with having an angle for output to be inclined as approximately three times as an angle of the waveguide 101 against the cleaved end face 102 due to a phenomenon of the refraction that is caused due to the difference on the indexes of refraction of between such the semiconductor and the air
Data Source
AI summary
A semiconductor laser element 10 according to the present invention comprises a waveguide 12 of a high mesa type. And then such the waveguide 12 comprises an oblique end face 17 as an emitting facet that is different from a cleaved end face 16. And hence it becomes possible to reduce a reflection factor at the end face by making of such the oblique end face 17, and it becomes possible to design a direction of an emitting beam 21, that is to be emitting from the oblique end face 17, to be independent of that for the cleaved end face 16 as well. Moreover, the emitting beam 21 is designed to be emitting as vertical to the cleaved end face 16. And then therefore in a case where an emitting beam from a semiconductor optical device is designed to be coupled with such as an optical fiber or another waveguide or the like, it is not necessary to device such as that the semiconductor laser element 10 is required to be arranged at a sub mount by being inclined to be oblique or the like.