Adiabatic Mode Converters for Low-Loss Grating Couplers
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Solution Overview
Problem
Conventional optical grating couplers are costly, cumbersome, and inefficient, often introducing asymmetry and higher-order mode generation due to differences in geometry and mode propagation between waveguides and grating regions, leading to significant light loss.
Innovation Solution
Incorporation of adiabatic mode converters with tapered sections at the waveguide-grating interface to gradually match the mode profile and propagation speed, minimizing reflections and higher-order mode excitation, thereby enhancing coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grating couplers are used to couple light between waveguides and the outside world, then light coupling is achieved, but coupling loss increases and coupling efficiency decreases
Solution Approach 1:
The patent applies parameter changes by transforming the grating structure from a two-dimensional planar pattern to a three-dimensional spherical or aspherical surface. This geometric parameter transformation enables the grating to focus and collimate light simultaneously, changing the light propagation parameters to achieve lower coupling loss and higher efficiency without altering the fundamental grating coupling mechanism
Solution Approach 2:
The invention transitions from a conventional two-dimensional planar grating to a three-dimensional spherical or aspherical grating structure. This dimensional change allows the grating to manipulate light in multiple spatial dimensions, creating focused beams with controlled divergence and achieving superior coupling efficiency compared to planar configurations
2Reliability
If conventional grating structures are used, then manufacturing is simplified, but coupling efficiency is limited
Solution Approach 1:
The patent replaces complex mechanical alignment systems with an optically optimized spherical or aspherical grating structure. The inherent focusing and collimating properties of the curved grating surfaces eliminate the need for complex mechanical adjustment mechanisms, achieving high coupling efficiency through geometric design rather than mechanical precision
Solution Approach 2:
The spherical or aspherical grating structure performs multiple functions simultaneously: it diffracts light, focuses the beam, and collimates the output. This multi-functionality consolidates what would otherwise require separate optical components into a single grating element, maintaining manufacturing simplicity while achieving superior performance
3Loss of energy
If light is coupled directly from waveguide to fiber, then connection is achieved, but coupling loss is high
Solution Approach 1:
The patent changes the light parameter distribution by using spherical or aspherical grating surfaces to transform divergent waveguide light into focused or collimated beams. This parameter transformation matches the spatial distribution of light between the waveguide and fiber, minimizing coupling loss without requiring precise alignment
4Ease of manufacture
If grating couplers are implemented, then light coupling is enabled, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes the geometric parameters of the grating from flat to spherical or aspherical surfaces, which inherently provide focusing and collimating functions. This parameter change reduces sensitivity to manufacturing variations in grating period and orientation, as the curved geometry compensates for small fabrication tolerances
Solution Approach 2:
The invention employs composite structures combining the grating pattern with curved substrate geometries (spherical or aspherical surfaces). This composite approach separates the diffraction function from the focusing function, allowing each to be optimized independently and reducing the overall manufacturing precision requirements
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
Significantly reduces light loss by suppressing parasitic effects, allowing for high-efficiency coupling of optical signals into and out of integrated circuits, with improved performance and reduced material costs.
Implementation Method 1
Grating couplers are used to couple light between waveguides and the outside world
Data Source
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AI summary
Methods and systems for mode converters for grating couplers may include a photonic chip comprising a waveguide, a grating coupler, and a mode converter, with the waveguide being coupled to the grating coupler via the mode converter. The mode converter may include waveguide material and tapers defined by tapered regions, where the tapered regions do not have waveguide material. The photonic chip may receive an optical signal in the mode converter from the waveguide, where the received optical signal has a light profile that may be spatially deflected in the mode converter to configure a desired profile in the grating coupler. A long axis of the tapers may be parallel to a direction of travel of the optical signal. The long axis of the tapers may point towards the input waveguide of the grating couplers, which may be linear.