3D Optical Waveguide with Tapered Silicon Core
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Solution Overview
Problem
The challenge in three-dimensional optical waveguide technology is to increase fabrication yield while reducing waveguide loss, as precise control of core widths is required to minimize propagation loss, making it difficult to achieve high-density optical interconnects with existing designs.
Innovation Solution
The optical waveguide configuration includes a silicon core with a taper region and multiple silicon nitride cores with specific taper and fixed sectional areas, arranged in a stereoscopic structure to guide light three-dimensionally with reduced loss, using a silicon-on-insulator substrate and SiO2 cladding layers, allowing for increased manufacturing tolerance and lower refractive index differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a three-dimensional cross waveguide with taper regions is used to reduce optical loss, then waveguide loss is reduced, but manufacturing precision requirements increase making fabrication more difficult
Solution Approach 1:
The patent transitions from two-dimensional planar waveguide crossing to three-dimensional waveguide configuration. By stacking waveguide layers at different heights (z-direction) and using vertical coupling through intermediate layers, the design eliminates the need for precise taper region control in planar crossings. The dimensional transition allows waveguides to cross without interaction by separating them in the vertical dimension, thereby reducing optical loss while relaxing manufacturing precision requirements.
Solution Approach 2:
The patent introduces intermediate layers (cladding layers and coupling layers) as mediators between waveguide cores. These intermediate layers facilitate controlled optical coupling while providing mechanical support and isolation. The intermediary layers absorb manufacturing tolerances and enable precise optical coupling without requiring extreme precision in core width fabrication, thus resolving the contradiction between low loss and ease of manufacture.
2Productivity
If high-density optical waveguide arrays are formed with small distances between waveguides, then optical interconnect density increases, but waveguide loss increases due to mode coupling
Solution Approach 1:
The patent utilizes vertical stacking of waveguide layers to achieve high density without increasing planar proximity. By arranging waveguides in multiple layers along the z-axis with intermediate cladding layers, the design achieves high interconnect density while maintaining sufficient vertical separation to prevent unwanted mode coupling. This dimensional arrangement allows dense packaging while preserving low loss characteristics.
Solution Approach 2:
The patent segments the optical path into multiple discrete layers separated by cladding and coupling layers. Each waveguide layer is independently structured with controlled thickness and material composition. This segmentation allows precise control of optical coupling between layers while maintaining high density, as each segment can be optimized independently for low loss transmission.
3Reliability
If SiO2 cladding layers are used with silicon cores to achieve high light confinement, then light confinement efficiency increases, but refractive index difference creates sensitivity to dimensional variations
Solution Approach 1:
The patent employs composite material structures with multiple cladding layers (SiO2, Si3N4, polymer materials) with different refractive indices surrounding the silicon core. This composite approach allows optimization of light confinement while reducing sensitivity to dimensional variations. The layered composite structure provides graded refractive index transitions that maintain strong confinement but are more tolerant of fabrication tolerances compared to single-material cladding.
Solution Approach 2:
The patent changes the refractive index parameter profile by introducing multiple cladding layers with different materials and thicknesses. By adjusting the refractive index distribution through material selection and layer thickness control, the design achieves optimal light confinement while creating a structure that is less sensitive to core dimensional variations. The parameter optimization balances confinement efficiency with manufacturing robustness.
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 enables efficient three-dimensional light propagation with reduced waveguide loss and increased fabrication yield, allowing for higher-density optical interconnects and lower propagation losses, while maintaining single-mode light guidance.
Implementation Method 1
an Si core is frequently covered with a SiO2 cladding layer to form an optical waveguide, and since the difference in refractive index between Si and SiO2 is great, light can be confined in a higher efficiency in the Si core
Implementation Method 2
one core having a taper region, which has a size that decreases toward a tip end thereof, is provided on a certain plane, and another core having a taper region, which has a size that decreases toward a tip end thereof, is provided on another plane having a distance from a substrate different from that of the one plane such that a tip end thereof opposes to that of the taper region of the one core so that propagation light is shifted in the heightwise direction
Data Source
AI summary
An optical waveguide includes a substrate, a first core provided over the substrate and having a first taper region that extends from one side toward the other side and has a sectional area that decreases toward the other side, and a plurality of second cores provided over the substrate and over or under the first core with a first cladding layer sandwiched therebetween and extending in parallel to the substrate and the first core.