Free Space Grating Coupler With Parallel Fiber Alignment
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Solution Overview
Problem
Direct butt coupling methods for optical fibers and silicon waveguides face challenges such as coupling loss, leakage, mechanical alignment difficulties, and increased production costs due to the need for precise alignment and fiber bending.
Innovation Solution
A free space coupling system using a silicon housing with a reflective surface and a lens-mirror configuration that allows for parallel alignment of the fiber to the waveguide, eliminating the need for direct butt coupling and reducing back reflections by focusing light onto a grating port, thereby minimizing coupling loss and mechanical complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct butt coupling is used to couple optical fiber to silicon waveguide, then coupling efficiency may be improved, but mechanical alignment difficulty and production cost increase
Solution Approach 1:
A housing structure is introduced as an intermediary component between the optical fiber and silicon waveguide. The housing provides a standardized mechanical interface with precision-machined alignment features (such as V-grooves or registration pins) that automatically guide the fiber into the correct position, eliminating the need for complex manual alignment procedures while maintaining coupling efficiency
Solution Approach 2:
The alignment features are pre-formed during the housing fabrication process rather than requiring post-assembly adjustment. The housing is manufactured with built-in mechanical guides and positioning structures that pre-establish the correct spatial relationship between fiber and waveguide, simplifying the assembly process and reducing production complexity
2Reliability
If direct butt coupling is used to couple optical fiber to silicon waveguide, then coupling efficiency may be improved, but production cost increases
Solution Approach 1:
The housing structure incorporates self-aligning mechanical features that automatically position the optical fiber relative to the silicon waveguide without requiring external alignment tools or complex assembly procedures. The self-service alignment mechanism reduces labor costs and simplifies the manufacturing process while maintaining high coupling efficiency
Solution Approach 2:
The coupling system is divided into separate modular components: the housing, the optical fiber, and the silicon waveguide. This segmentation allows each component to be manufactured independently using optimized processes, with the housing serving as a reusable platform that can accommodate different waveguide types, thereby reducing overall production cost
3Reliability
If fiber is bent for coupling alignment, then coupling efficiency may be improved, but mechanical stability and reliability deteriorate
Solution Approach 1:
The housing acts as a rigid intermediary structure that supports both the optical fiber and silicon waveguide in fixed, stress-free positions. By providing a stable mechanical platform with precision-machined mounting features, the housing eliminates the need to bend or stress the fiber, maintaining both coupling efficiency and mechanical stability simultaneously
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 approach reduces coupling loss, minimizes mechanical alignment issues, and lowers production costs while enabling wider bandwidths and more compact packaging, accommodating a range of beam mode diameters including smaller ones suitable for coarse wavelength division multiplexing.
Implementation Method 1
a lens positioned in the housing for conditioning light communicated between the light element and the waveguide
Implementation Method 2
a mirror positioned in the housing, wherein the lens and the mirror are configured such that a first light received from the light element is focused on the grating port
Data Source
AI summary
A free space coupling system comprising a waveguide horizontally positioned on an integrated circuit, and a silicon housing coupled to the waveguide, wherein the silicon housing comprises a reflective surface, a first port, wherein the first port is configured to receive light from an optic source positioned substantially parallel to the waveguide at a coupling point, and a second port, wherein the second port is oriented at about ninety degrees with respect to the first port, and wherein the second port is aligned with a grating port on the waveguide.