Double-Layer Bragg Grating Waveguide for CMOS Fabrication
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Solution Overview
Problem
Conventional optical add/drop multiplexers with single Bragg grating waveguides face processing difficulties due to stringent requirements for small grating sizes, especially in silicon optical technology, which are challenging to meet, especially for dense wavelength division multiplexing applications.
Innovation Solution
The use of a double-layer waveguide structure in the Bragg grating waveguide with alternating widths for the upper and lower layers reduces light restriction, allowing for a larger grating size while maintaining the required reflectance spectrum bandwidth, thereby simplifying the processing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer Bragg grating waveguide is used, then the coupling factor increases due to strong light restriction, but the grating size becomes very small (tens of nanometers) making CMOS processing difficult
Solution Approach 1:
The patent transitions from a single-layer waveguide to a double-layer waveguide structure, adding a vertical dimension to the design. This dimensional change allows the system to achieve the required coupling factor through the combined effect of two layers with different refractive indices, thereby relaxing the horizontal grating size requirement and making CMOS processing feasible.
Solution Approach 2:
The patent employs a composite waveguide structure consisting of two layers with different refractive indices (n1 and n2). This composite approach allows the system to achieve stronger and more controllable light restriction through the interaction between layers, enabling the use of larger grating sizes while maintaining the necessary coupling factor for DWDM applications.
2Reliability
If a small grating size is used to achieve proper coupling factor in single-layer waveguide, then the coupling factor is sufficient, but the processing difficulty increases greatly for CMOS technology
Solution Approach 1:
By introducing a vertical dimension through the double-layer structure, the patent distributes the light restriction function across two layers. This allows each layer to contribute to the overall coupling effect, enabling the use of larger, more manufacturable grating sizes that are compatible with standard CMOS processing capabilities.
Solution Approach 2:
The patent changes the structural parameters by introducing a second waveguide layer with a different refractive index. This parameter change fundamentally alters how light is restricted and coupled, allowing the system to achieve the required performance with grating sizes that are much more amenable to CMOS manufacturing processes.
3Manufacturing precision
If a double-layer waveguide structure is used, then the grating size can be larger reducing processing difficulty, but the structure complexity increases
Solution Approach 1:
The patent adds a vertical layer to the waveguide structure, transitioning from 2D to 3D configuration. While this increases structural complexity, it simultaneously enables the use of larger grating sizes that are much easier to manufacture with standard CMOS processes, representing a worthwhile trade-off for achieving manufacturability.
Solution Approach 2:
The composite double-layer waveguide structure, while more complex than a single layer, provides superior control over light propagation and coupling. The increased structural complexity is justified by the significant improvement in manufacturability and the ability to achieve the required coupling factor with much larger, more tolerant grating dimensions.
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 enables the use of larger grating sizes, reducing processing difficulties and maintaining the necessary coupling factor for efficient signal separation and reflection, thus improving the feasibility of implementing optical add/drop multiplexers in silicon optical technology.
Implementation Method 1
the Bragg grating waveguide is configured to: receive the optical signals that are in the first mode and that are sent by the first transmission mode converter; and reflect, to the first transmission mode converter as an optical signal that is in a second mode, an optical signal that has a predetermined wavelength and that is of the optical signals that are in the first mode
Data Source
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AI summary
Embodiments of this application relate to the field of optoelectronic technologies and disclose an optical add/drop multiplexer, so that a fiber Bragg grating of a relatively large size can be used, thereby reducing a processing difficulty. The optical add/drop multiplexer includes a drop signal separator (11) and a drop signal reflector (12). The drop signal separator (11) is connected to a main input end and a drop end. The drop signal separator (11) is connected to the drop signal reflector (12), and the drop signal reflector (12) is connected to a main output end.