Optical Waveguide Rectangular Core Slab Layer
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Solution Overview
Problem
In silicon photonics, the equivalent refractive index of optical waveguides is sensitive to processing errors such as core width and height fluctuations, making it difficult to manufacture arrays of optical waveguides with varying path lengths, such as in arrayed waveguide gratings, which requires an additional phase adjustment function.
Innovation Solution
An optical waveguide configuration featuring a semiconductor core with a rectangular cross-section and a semiconductor slab layer, optically coupled and separated by an insulator spacer layer, which stabilizes the equivalent refractive index against manufacturing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithography and etching are used to process the surface Si layer to form optical waveguides, then optical waveguides can be manufactured, but the equivalent refractive index fluctuates sensitively with processing errors such as core width and height variations
Solution Approach 1:
The patent employs a composite structure consisting of a Si core layer and an InGaAsP cladding layer with different refractive indices. This composite material approach creates an optical waveguide where the light confinement is achieved through the refractive index contrast between layers, making the equivalent refractive index less sensitive to dimensional variations in the Si core layer caused by lithography and etching processing errors.
2Ease of operation
If the equivalent refractive index is made stable against processing errors, then phase adjustment becomes easier in arrayed waveguide gratings, but the structural complexity increases due to the additional slab layer
Solution Approach 1:
The InGaAsP slab layer serves multiple functions: it acts as a cladding layer providing optical confinement, serves as a buffer layer that stabilizes the equivalent refractive index against processing errors, and enables better integration with other semiconductor optical devices. This multi-functionality reduces the need for additional phase adjustment mechanisms while the structural increase is justified by the multiple benefits provided.
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 reduces the sensitivity of the equivalent refractive index to processing errors, facilitating the manufacture of optical waveguides with reduced phase adjustment difficulties, particularly in arrayed waveguide gratings, by maintaining refractive index stability during manufacturing.
Implementation Method 1
a slab layer that is laminated on the clad layer with the core to be optically coupled to the core
Data Source
AI summary
A core and a slab layer that are formed on a lower clad layer are provided. The lower clad layer is formed on a substrate. The core is comprised of a semiconductor and has a rectangular shape in a cross-sectional view. The slab layer is comprised of a semiconductor. The core and the slab layer have a thickness that allows only up to a secondary mode of light to be present. Further, the core and the slab layer are laminated on the lower clad layer. Further, the core and the slab layer are disposed to be optically coupled to each other.