Interposer Beam Expander Chip for Fiber-to-Waveguide Coupling
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Solution Overview
Problem
Efficient and cost-effective optical coupling into or out of optical waveguides in photonic integrated circuits is challenging due to requirements for mode size or shape changes and precise alignment, increasing assembly costs.
Innovation Solution
An interposer chip with V-grooves for fiber alignment and tapered optical waveguides that reduce vertical mode size, combined with a hard stop for vertical alignment, enables efficient coupling between an array of fibers and optical waveguides on a second photonic chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mode size changes and precise alignment are implemented for efficient optical coupling, then coupling efficiency is improved, but assembly cost increases
Solution Approach 1:
The patent introduces an interposer chip as an intermediary component between the fiber array and the photonic integrated circuit. This interposer chip contains optical waveguides with tapered sections that mediate the mode size transformation, eliminating the need for direct complex alignment and mode matching between fibers and the PIC, thereby reducing assembly cost while maintaining coupling efficiency
Solution Approach 2:
The optical waveguides in the interposer chip feature tapered sections where the width parameter changes gradually along the propagation direction. This parameter change enables adiabatic mode transformation, allowing efficient coupling between different mode sizes without requiring precise mechanical alignment, thus resolving the contradiction between coupling efficiency and assembly cost
2Reliability
If mode size transformation is implemented for efficient coupling, then optical coupling efficiency is improved, but device complexity increases
Solution Approach 1:
The coupling system is segmented into distinct functional components: a fiber array, an interposer chip with multiple optical waveguides, and a photonic integrated circuit. Each waveguide is further segmented into sections with different width characteristics (tapered section, first section, second section), allowing independent optimization of each segment's function while simplifying the overall design
Solution Approach 2:
The interposer chip acts as an intermediary that handles the complex mode transformation task, isolating the complexity from both the fiber array and the photonic integrated circuit. This mediator approach distributes the complexity across a dedicated component rather than requiring complex structures in the main systems
3Manufacturing precision
If precise alignment features are added to the photonic chip, then alignment precision is improved, but manufacturing complexity increases
Solution Approach 1:
The optical waveguides are designed with self-aligning features including tapered sections and flat facets that automatically guide the fiber positioning during assembly. The tapered geometry provides mechanical guidance that naturally aligns the fiber with the waveguide mode, enabling self-alignment without requiring additional active alignment steps or complex adjustment mechanisms
Solution Approach 2:
The interposer chip is pre-fabricated with precisely positioned optical waveguides, tapered sections, and alignment features before assembly. This preliminary fabrication of the interposer chip with built-in alignment references allows for simplified final assembly, as the alignment work is performed during the controlled fabrication process rather than during system assembly
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 interposer chip facilitates efficient light coupling by aligning and reducing mode size, reducing assembly costs and improving alignment precision, allowing for efficient optical communication between fibers and photonic chip waveguides.
Implementation Method 1
Each optical waveguide has a taper with a first end and a second end, the first end being configured to support an optical mode that couples efficiently to the mode of an optical fiber. The taper reduces the vertical mode size, so that the mode supported by the second end of the taper may be efficiently coupled to a 3-micron thick optical waveguide on the second photonic chip.
Data Source
AI summary
An interposer chip for coupling light between an array of fibers and an array of optical waveguides on a second photonic chip. The interposer chip has an array of V-grooves for aligning the ends of the fibers to corresponding ends of an array of optical waveguides on the interposer chip. Each optical waveguide has a taper with a first end and a second end, the first end being configured to support an optical mode that couples efficiently to the mode of an optical fiber. The taper reduces the vertical mode size, so that the mode supported by the second end of the taper may be efficiently coupled to a 3-micron thick optical waveguide on the second photonic chip. The interposer chip further has a hard stop having a flat surface parallel to the optical waveguides on the interposer chip, at the interface to the second chip. When the interposer chip is flipped and assembled with the second chip, the hard stop abuts against a mounting surface on the second chip, so that optical waveguides on the interposer chip are aligned, in the vertical direction, with optical waveguides on the second chip.