Grating Coupler Fiber-to-Waveguide Interconnects
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Solution Overview
Problem
Conventional optical fiber-to-waveguide couplers face inefficiencies, particularly in coupling light between single mode fibers and waveguides, due to the need for precise alignment and complex packaging, which increases costs and reduces efficiency.
Innovation Solution
The use of a grating coupler with a tapered waveguide and a non-periodic sub-wavelength grating (SWG) layer at the end of the optical fiber, which allows for efficient light coupling without requiring the fiber to be tilted, by directing light at an angle and utilizing sub-wavelength gratings to manage light phase and polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional grating coupler is used to couple light between waveguide and optical fiber, then light coupling is achieved, but the fiber must be positioned at an angle from normal which complicates the design and packaging of the chip
Solution Approach 1:
Instead of tilting the fiber to match the grating's scattering angle, the patent inverts the approach by using a tilted incident beam to achieve normal output coupling. The grating is designed with a specific tilt angle that converts the angled input from the fiber into a normal output beam, eliminating the need for angled fiber positioning and simplifying the packaging.
Solution Approach 2:
The patent changes the operational parameters of the grating coupler by introducing a specific tilt angle for the incident beam and designing the grating geometry to compensate for this tilt. By adjusting the grating period, depth, and tilt angle, the system achieves efficient coupling with normal fiber positioning, transforming the conventional angled-output configuration into a normal-output configuration.
2Productivity
If the fiber is positioned at an angle for efficient coupling with conventional grating coupler, then coupling efficiency is improved, but the design and packaging of the chip is complicated
Solution Approach 1:
The patent inverts the conventional approach by using a tilted incident beam instead of a normal incident beam. The grating is specifically designed to convert this tilted input into a normal output, achieving high coupling efficiency while maintaining simple normal positioning of the fiber, thereby eliminating the packaging complexity associated with angled fiber positioning.
Solution Approach 2:
The patent modifies the grating parameters including period, depth, and tilt angle to optimize the conversion of tilted incident light into normal output light. By carefully selecting these parameters, the system achieves high coupling efficiency without requiring angled fiber positioning, thus resolving the contradiction between efficiency and packaging simplicity.
3Ease of operation
If conventional techniques are used to couple light from waveguide into optical fiber with lens, then light direction control is achieved, but the mode matching between fiber core and captured light must be closely matched which reduces efficiency
Solution Approach 1:
The patent replaces the mechanical lens-based light direction control system with a grating-based diffraction system. The grating coupler uses diffraction to directly control the direction of light from the waveguide, eliminating the need for separate lens components and reducing the complexity of mode matching requirements while maintaining effective light direction control.
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 enhances coupling efficiency by eliminating the need for fiber tilting, reduces packaging complexity, and improves light transmission by managing light phase and polarization, thereby enhancing the overall performance of optical fiber-to-waveguide interconnects.
Implementation Method 1
Light coming from the waveguide propagates through the grating and is scattered in free space at some finite angle from normal
Implementation Method 2
utilizing sub-wavelength gratings to manage light phase and polarization
Implementation Method 3
a tapered guiding portion for converting the mode size between the fiber and the planar waveguide
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
Embodiments of the present invention are directed to optical waveguide- to-fiber interconnects. In one aspect, an optical fiber-to-waveguide interconnect includes a grating coupler (102) located at the end of a waveguide, and a grating layer (110) disposed on the end of an optical fiber (112). The optical fiber includes a core (118) and the grating layer includes a planar, non-periodic, sub-wavelength grating (116). Light carried by the waveguide into the grating coupler is output and coupled into the core via the sub-wavelength grating, and light transmitted along the core to the grating layer is directed by the sub-wavelength grating into the grating coupler for transmission in the waveguide.