Grating Coupler Backside Recess and Reflector
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Solution Overview
Problem
Current photonics devices face challenges in achieving high coupling efficiency while maintaining manufacturability, particularly in the silicon photonics platform, where complex processing steps and custom-made substrates are required, leading to increased costs and defects.
Innovation Solution
A semiconductor photonics device using a conventional semiconductor-on-insulator substrate with a grating coupler on top of the buried oxide layer and a recessed portion at the backside for radiation coupling, optionally incorporating a reflector above the grating coupler to enhance efficiency, allowing the use of standard SOI wafers and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reflector is implemented below the buried oxide layer to increase coupling efficiency, then the amount of light coupled to the waveguide increases, but custom-made silicon-on-insulator wafers are required, rendering manufacturing less trivial
Solution Approach 1:
Instead of placing the reflector below the buried oxide layer (conventional approach), the patent inverts the structure by placing the reflector above the grating coupler. This inversion allows the use of standard silicon-on-insulator wafers while maintaining enhanced coupling efficiency, as the reflector is positioned to reflect light back through the grating without requiring substrate modification or custom wafer fabrication.
Solution Approach 2:
The patent moves the reflector from the vertical dimension (below the substrate) to the horizontal dimension (above the grating coupler on the same substrate layer). This dimensional repositioning allows the reflector to function effectively while兼容ing with standard manufacturing processes, as it eliminates the need for backside processing or custom substrate preparation.
2Reliability
If substrate removal and metal deposition are performed to implement a mirror under the grating, then coupling efficiency increases, but the processing steps become complex
Solution Approach 1:
The patent inverts the conventional mirror implementation by placing the reflector above rather than below the grating coupler. This eliminates the need for substrate removal and complex metal deposition steps, as the reflector can be integrated into the existing layer structure using standard semiconductor fabrication processes.
Solution Approach 2:
The patent extracts the reflector from the substrate layer and places it in the cladding layer above the grating. This extraction eliminates the need for complex substrate modification steps such as etching, substrate removal, and metal deposition, simplifying the overall manufacturing process while maintaining the light-reflection function.
3Reliability
If silicon grating is applied by locally increasing silicon waveguide thickness to increase coupling efficiency, then efficiency improves, but tight control of geometrical dimensions is required for controlling grating spectral response
Solution Approach 1:
The patent segments the coupling structure into distinct functional layers: the grating coupler in the silicon waveguide layer and the reflector in the upper cladding layer. This segmentation allows each component to be optimized independently, reducing the need for tight dimensional control across the entire structure and simplifying manufacturing tolerances.
Solution Approach 2:
The reflector acts as an intermediary element that enhances the coupling function of the grating without requiring the grating itself to be complex. By introducing this intermediate reflector layer, the system achieves high coupling efficiency through a simpler grating structure with more relaxed dimensional tolerances.
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 efficient radiation coupling with standard substrates, increasing coupling efficiency and reducing manufacturing complexity, while allowing for high integration of active components and minimal thermal dependency.
Implementation Method 1
a grating coupler positioned on top of the buried oxide layer and configured for coupling incident radiation to the semiconductor waveguide
Implementation Method 2
The semiconductor substrate has a recessed portion at the backside of the semiconductor substrate for receiving incident radiation to be coupled to the semiconductor waveguide via the backside of the semiconductor substrate
Data Source
AI summary
Semiconductor photonics devices for coupling radiation to a semiconductor waveguide are described. An example photonics device comprises a semiconductor-on-insulator substrate comprising a semiconductor substrate, a buried oxide layer positioned on top of the semiconductor substrate, and the semiconductor waveguide on top of the buried oxide layer to which radiation is to be coupled. The example device also comprises a grating coupler positioned on top of the buried oxide layer and configured for coupling incident radiation to the semiconductor waveguide. The semiconductor substrate has a recessed portion at the backside of the semiconductor substrate for receiving incident radiation to be coupled to the semiconductor waveguide via the backside of the semiconductor substrate and the grating coupler.