Enlarged Multilayer Nitride Waveguide for Low-Loss Photonic Integration
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Solution Overview
Problem
Existing nitride waveguides in photonic integrated circuits (PICs) exhibit unsatisfactory propagation losses, particularly when interfacing with single-mode optical fibers.
Innovation Solution
The implementation of an enlarged multilayer nitride waveguide with a cladding layer of lower refractive index than the nitride body, positioned in an inter-level dielectric layer, along with optically side-coupled waveguides to reduce propagation losses and allow mode shape changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the waveguide is made vertically short for integration with CMOS devices, then the integration compatibility is improved, but the propagation losses increase
Solution Approach 1:
The patent transitions from vertical waveguide extension to lateral enlargement of the waveguide cross-section. By increasing the width and height dimensions of the nitride waveguide core while maintaining short vertical profile for CMOS integration, the patent achieves mode shape transformation that enables efficient coupling to single-mode fibers without increasing propagation losses
Solution Approach 2:
The patent modifies the refractive index distribution by introducing a cladding layer with lower refractive index than the nitride body. This parameter change in the optical confinement structure enables better mode confinement and reduces propagation losses while maintaining the short vertical dimension for integration compatibility
2Loss of energy
If the waveguide is enlarged to reduce propagation losses, then the propagation losses decrease, but the device complexity increases
Solution Approach 1:
The patent segments the waveguide structure into distinct functional layers: a nitride body layer for optical confinement, a lower cladding layer with lower refractive index for mode shaping, and an upper cladding layer. This segmentation allows each layer to be optimized independently for its specific function while maintaining overall structural simplicity
Solution Approach 2:
The patent employs composite material structure combining nitride materials with different refractive indices arranged in multiple layers. This composite structure achieves superior optical performance with reduced propagation losses while maintaining fabrication compatibility with standard semiconductor processes
3Adaptability or versatility
If the waveguide is enlarged for better fiber coupling, then the mode shape compatibility with single-mode fiber is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent performs preliminary planarization of the upper cladding layer surface before subsequent processing steps. This preliminary action creates a flat reference surface that simplifies alignment and reduces the precision requirements for subsequent fiber coupling operations
Solution Approach 2:
The patent applies different material properties and structural characteristics to different regions of the waveguide: the nitride body provides strong optical confinement, the lower cladding layer with lower refractive index provides mode shaping at the interface, and the upper cladding provides protection and structural support. This local optimization allows each region to contribute to overall performance while maintaining manufacturability
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 significantly reduces propagation losses, allows for shorter directional coupling between waveguides, and enhances the integration of ultra-low-loss nitride waveguides with silicon waveguides and CMOS devices, improving the performance of photonic integrated circuits.
Implementation Method 1
a first cladding layer on at least a lower surface of the first nitride body, wherein the first cladding layer has a lower refractive index than the first nitride body
Data Source
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AI summary
Structures and methods implement an enlarged multilayer nitride waveguide. The structure may include an inter-level dielectric (ILD) layer over a substrate. A first enlarged multilayer nitride waveguide is positioned in the ILD layer in a region of the substrate. A second multilayer nitride waveguide may also be provided in the ILD layer. A lower cladding layer defines a lower surface of the nitride waveguide(s). The lower cladding layer has a lower refractive index than the nitride waveguide(s). Additional lower refractive index cladding layers can be provided on the upper surface and/or sidewalls of the nitride waveguide(s). The enlarged nitride waveguide may be implemented with other conventional silicon and nitride waveguides.