Focusing Grating for Out-of-Plane Optical Coupling
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Solution Overview
Problem
Existing solutions for coupling light between a planar waveguide and an out-of-plane light source/receiver, such as VCSELs, fail to efficiently bridge gaps of 30 to 300 microns with minimal optical losses and beam divergence, often requiring complex and costly lenses or gratings that are difficult to manufacture using standard CMOS fab tools.
Innovation Solution
An optical coupling arrangement that integrates a focusing grating within the waveguide layer, designed for out-of-plane coupling with a focal distance between 30 and 300 microns, combined with a refractive surface like a prism to deviate the light beam, avoiding the use of lenses and utilizing standard lithography and etching techniques for fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lens is used to focus light between the waveguide and light source, then light coupling efficiency is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the focusing function from a separate lens component and integrates it directly into the waveguide structure through etched grooves. This eliminates the need for a discrete lens while maintaining the light focusing capability, thereby reducing device complexity and manufacturing steps while preserving light coupling efficiency.
Solution Approach 2:
The patent combines the light guiding function and light focusing function into a single integrated waveguide structure. The grooves etched into the waveguide serve dual purposes: guiding light along the waveguide and focusing light at the coupling point, thereby reducing the number of components and simplifying the overall device architecture.
2Length of stationary object
If a micro-lens is used to reduce focal distance, then light focusing capability is improved, but fabrication complexity increases
Solution Approach 1:
The patent replaces the mechanical micro-lens fabrication process with a standard semiconductor etching process. Instead of using complex micro-lens fabrication techniques, the patent uses conventional lithography and etching to create grooves in the waveguide that provide the necessary focusing capability, thereby simplifying fabrication and enabling compatibility with standard CMOS manufacturing processes.
Solution Approach 2:
The patent changes the physical structure of the waveguide by etching grooves with specific dimensions and patterns. By controlling the groove depth, width, spacing, and curvature, the patent achieves the desired focal distance without requiring a separate micro-lens component, thereby simplifying fabrication while maintaining focusing capability.
3Reliability
If a grating coupler with hyperbolic sidewalls and elliptic scattering elements is used, then optical coupling efficiency is improved, but manufacturing simplicity deteriorates
Solution Approach 1:
The patent modifies the grating coupler structure by using straight or slightly curved grooves instead of complex hyperbolic sidewalls and elliptic scattering elements. By adjusting parameters such as groove depth, width, spacing, and curvature radius, the patent achieves satisfactory optical coupling efficiency while maintaining compatibility with standard lithography and etching processes, thereby simplifying manufacturing.
Solution Approach 2:
The patent applies local quality by creating grooves with varying depth, width, and spacing at different locations along the waveguide. This localized variation in groove parameters allows the grating coupler to achieve efficient optical coupling without requiring complex global structures, thereby simplifying manufacturing while maintaining performance.
4Reliability
If the gap between waveguide and light source is reduced, then light coupling efficiency is improved, but adaptability to different light source configurations deteriorates
Solution Approach 1:
The patent introduces a movable or adjustable component (such as a movable lens or adjustable waveguide position) that allows the system to adapt to different light source configurations. This dynamic adjustment capability enables efficient light coupling for various gap distances and light source types without requiring a complete redesign of the coupling structure.
Solution Approach 2:
The patent designs the grating coupler and waveguide structure to serve multiple functions: coupling light from different types of light sources (VCSELs, edge-emitting lasers), accommodating different gap distances, and working with various light wavelengths. This universal design approach maintains light coupling efficiency across different configurations without requiring specialized structures for each case.
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 solution enables efficient and accurate light coupling with minimal optical losses and divergence across the specified gap, using standard manufacturing processes in a CMOS fab, while maintaining high precision and cost-effectiveness.
Implementation Method 1
a refractive surface positioned between the VCSEL and the integrated optical waveguide and shaped to refract the light emitted by the VCSEL over an angle of at least 3 degrees
Implementation Method 2
integrating a focusing grating in the waveguide layer, and designing the focusing grating for out-of-plane coupling light from a light source
Data Source
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AI summary
An optical coupling arrangement for coupling light (105; 205; 305) between an integrated optical waveguide (110; 210; 310) and a light source/receiver (120; 220; 320) comprises: - a substrate (101; 201; 301); - one or more undercladding layers (102; 202; 302); - a core layer (103; 203; 303) comprising the integrated optical waveguide (110; 210; 310); and - one or more overcladding layers (104; 204; 304). The core layer (103; 203; 303) further comprises a focusing grating (130; 230; 330; 430; 530) designed for out-of-plane coupling between the integrated optical waveguide (110; 210; 310) and the light source/receiver (120; 220; 320). This focusing grating (130; 230; 330; 430; 530; 630) comprises an ellipse arc shaped pattern (431-441; 531-541; 631-638) designed to focus the light (105; 205; 305) over a focusing distance of at least 30 microns and at most 300 microns.