Optical Waveguide Spatially Modulated Index Region Misalignment
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Solution Overview
Problem
Efficient coupling of light into small-core photonic integrated circuits (PICs) and other small-scale optical devices is challenging due to the large difference in refractive indices between silicon waveguide cores and claddings, leading to misalignment sensitivity and dust effects.
Innovation Solution
An optical waveguide with a spatially modulated index region, comprising alternating higher and lower index regions, is designed to extract optical modes, featuring a length greater than 30 microns, which reduces the impact of lateral misalignment and supports multiple optical modes, allowing for efficient coupling with expanded beam approaches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If small-core PIC waveguides are used, then integration density is improved, but coupling efficiency with optical fibers deteriorates due to misalignment sensitivity
Solution Approach 1:
The waveguide structure is segmented into multiple regions with different refractive indices (core region, cladding regions, and intermediate regions). This segmentation allows the waveguide to maintain a small core area while having extended interaction regions that improve coupling tolerance to misalignment
Solution Approach 2:
Different regions of the waveguide are assigned different local optical properties (refractive indices). The core region has high index for confinement, while cladding and intermediate regions have lower indices to enable mode matching and reduce sensitivity to alignment errors, thus improving coupling efficiency without increasing core area
2Area of moving object
If small-core PIC waveguides are used, then integration density is improved, but sensitivity to dust and misalignment increases
Solution Approach 1:
Intermediate regions with refractive indices between the core and outer cladding act as mediators. These regions create a gradual transition that reduces the impact of dust particles and misalignment by distributing the optical field more broadly, thereby reducing sensitivity to harmful factors while maintaining the small core area
Solution Approach 2:
The waveguide structure extends in the vertical dimension with multiple layers (core, cladding, intermediate regions) to create a larger effective interaction area. This dimensional extension compensates for the small horizontal core area, reducing sensitivity to dust and misalignment in the lateral direction
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 optical waveguide effectively couples light to and from optical fibers with reduced sensitivity to misalignment and dust, enhancing the integration of PICs into large-scale systems while maintaining low loss and insensitivity to position.
Implementation Method 1
a spatially modulated index region comprising alternating higher and lower index regions extending along a width, and arranged along the length, of the optical waveguide and configured to extract an optical mode that would otherwise propagate along the length of the waveguide
Implementation Method 2
an optical core having first and second optical core portions sequentially arranged along the length of the waveguide and having different respective first and second indices of refraction... a first optical cladding disposed adjacent the optical core and extending along the first and second optical core portions
Data Source
AI summary
An optical waveguide propagates an optical mode at a first wavelength along a length of the waveguide. The optical waveguide has an optical core with a substantially polygonal cross-section in a plane substantially perpendicular to the length of the waveguide. The optical core has an index of refraction n1 at the first wavelength. A first optical cladding is disposed adjacent the optical core and has an index of refraction n2 at the first wavelength, n2<n1. A spatially modulated index region has alternating higher and lower index regions extending along a width, and arranged along the length, of the optical waveguide, and configured to extract an optical mode that would otherwise propagate along the length of the waveguide.