Y-Shaped Spotsize Converter for Fiber-to-Chip Coupling
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Solution Overview
Problem
High coupling loss between silicon-based photonic integrated circuits (PICs) and single-mode optical fibers due to mismatched spot sizes and refractive indices, making effective optical signal transmission challenging.
Innovation Solution
A spotsize converter with a Y-shaped waveguide structure, including a substrate layer, a first coverage layer, an isolating layer, and a waveguide with specific refractive index differences and geometrical configurations to reduce coupling loss by gradually increasing the width of the third waveguide and decreasing the distance between the first and second waveguides, forming a Y shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional spotsize converter is used, then the coupling loss is reduced, but the coupling loss remains relatively large
Solution Approach 1:
The waveguide is divided into three segments (first waveguide, second waveguide, and third waveguide) arranged in a Y-shape. Each segment serves a specific function in the mode field transformation process, allowing gradual and controlled transition from fiber mode to chip mode, thereby reducing coupling loss and improving coupling efficiency.
Solution Approach 2:
The patent introduces a vertical dimension by stacking multiple waveguide layers (first coverage layer, isolating layer, substrate layer) to create a three-dimensional Y-shaped structure. This vertical stacking enables more effective mode field matching by controlling light propagation through multiple layers with different refractive indices, achieving lower coupling loss than planar designs.
2Reliability
If the waveguide width is gradually increased, then the mode field matching is improved, but the device length increases
Solution Approach 1:
The patent uses vertical stacking of waveguide layers to achieve mode field transformation in the vertical dimension rather than solely in the horizontal dimension. This allows the converter to achieve effective mode matching with a more compact overall length by utilizing the third dimension (vertical stacking of isolating layer, first coverage layer, substrate layer) for light confinement and transformation.
Solution Approach 2:
Different segments of the Y-shaped waveguide have locally optimized properties: the first and second waveguides have specific widths and spacing for optimal mode coupling, while the third waveguide has gradually varying dimensions. The isolating layer and coverage layers have specific refractive index properties tailored to their local positions, enabling efficient mode transformation within a compact length.
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 Y-shaped spotsize converter effectively reduces coupling loss between the optical fiber and the PIC, allowing for improved optical signal transmission with reduced alignment requirements and lower losses, achieving coupling losses less than 1.5 dB for both TE and TM modes.
Implementation Method 1
a difference between a refractive index of the second material and a refractive index of the first material is less than a first threshold, and a difference between a refractive index of the third material and a refractive index of the first material is greater than a second threshold
Data Source
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AI summary
A spotsize converter (200) includes a substrate layer (201); a first coverage layer (202) disposed above the substrate layer (201); an isolating layer (203) disposed between the substrate layer (201) and the first coverage layer (202); and a waveguide (204) disposed inside the first coverage layer (202), where the waveguide (204) is symmetrical along a principal axis. The waveguide (204) includes an equal-width first waveguide (301), an equal-width second waveguide (302), and a third waveguide (303). A first end of the third waveguide (303) is connected to a first end of the first waveguide (301) and a first end of the second waveguide (302), and the first waveguide (301), the second waveguide (302), and the third waveguide (303) form a Y shape. Along a first direction of the principal axis, a width of the third waveguide (303) gradually increases, and a distance, in a second direction, between the first waveguide (301) and the second waveguide (302) gradually decreases. The spotsize converter (200) can be used to implement spot size conversion between an optical fiber and an optical waveguide, and a coupling loss between the optical fiber and the optical waveguide can be reduced by using the spotsize converter (200).