Optical Waveguide Coupler with Convex Protrusion for Elliptical Beam Matching
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Solution Overview
Problem
Conventional optical waveguide couplers face significant coupling loss when dealing with semiconductor lasers having elliptical beam spots, particularly those narrow in the vertical direction, such as quantum dot lasers, due to mode mismatching and inadequate light confinement.
Innovation Solution
An optical waveguide coupler with a multi-layer structure featuring a first waveguide layer with a refractive index distribution where the center has the highest refractive index, and a protrusion that acts as a convex or hemispherical lens to optimize light coupling, allowing for efficient coupling with semiconductor lasers having elliptical beam spots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional optical waveguide coupler with a flat end surface is used, then the structure is simple and easy to manufacture, but coupling loss is significant when dealing with semiconductor lasers having elliptical beam spots
Solution Approach 1:
The patent applies spheroidality by transforming the flat end surface of the waveguide into a convex curved surface (hemispherical or spherical shape). This curved surface acts as a lens that focuses and shapes the light beam, enabling better mode matching with elliptical beam spots from semiconductor lasers. The curvature radius is specifically designed to be 0.5-2.0 times the waveguide width to optimize coupling efficiency while maintaining manufacturability through standard semiconductor processing techniques.
2Loss of energy
If the waveguide end surface is made into a semi-cylindrical lens form, then coupling efficiency with certain beam spots is improved, but coupling loss remains great for beam spots narrow in the vertical direction
Solution Approach 1:
The patent applies asymmetry by designing the waveguide end surface with different curvature characteristics in different directions. The convex curved surface has a curvature radius that is specifically related to the waveguide width, creating an asymmetric profile that can adapt to elliptical beam spots. This asymmetric curvature allows the waveguide to effectively couple with beam spots that are narrow in the vertical direction, unlike the symmetric semi-cylindrical lens form.
Solution Approach 2:
The patent applies parameter changes by optimizing the curvature radius of the convex curved surface to be 0.5-2.0 times the waveguide width. This parameter optimization enables the waveguide to effectively couple with various beam spot sizes and shapes. By adjusting this key geometric parameter, the waveguide achieves high coupling efficiency with quantum dot lasers and other semiconductor lasers having elliptical beam spots, while maintaining broad adaptability.
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 proposed solution significantly reduces coupling loss, achieving a coupling efficiency approximately 1.5 times greater than conventional methods, with a maximum efficiency of about 70% and improved light propagation with minimal attenuation.
Implementation Method 1
the first waveguide layer has such a protrusion that the center portion having the highest refractive index protrudes in a cross section that is perpendicular to the end surface through which light enters and exits
Implementation Method 2
the first waveguide layer has such a distribution of the refractive index that the refractive index is the highest at the center of the first waveguide layer
Data Source
AI summary
An optical waveguide coupler includes a substrate and an optical waveguide of a multi-layer structure of a first clad layer/a first waveguide layer/a second clad layer, at least, on the end surface side of an optical input and output provided on the substrate, characterized in that the first waveguide layer has such a distribution of the refractive index that the refractive index is the highest at the center of the first waveguide layer in the multi-layer structure in the stacking direction, and the first waveguide layer has such a protrusion in a convex form that the center portion having the highest refractive index protrudes in a cross section that is perpendicular to the end surface of the optical input and output and perpendicular to the main surface of the substrate.