X-cut Lithium Niobate Waveguide Stepped Buffer Electrodes
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Solution Overview
Problem
Conventional thin-film LN optical modulators face a tradeoff between reducing scattering loss and improving electric field efficiency due to the thickness of the buffer layer, which affects the size and performance of the device.
Innovation Solution
The optical waveguide device features a thin-film LN layer with X-cut lithium niobate and a buffer layer with a predetermined thickness, where electrodes are positioned on steps etched in the buffer layer to be closer to the optical waveguide, reducing scattering loss and enhancing electric field efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the buffer layer thickness is increased to reduce scattering loss, then scattering loss is reduced, but electric field efficiency deteriorates
Solution Approach 1:
The invention transitions from a conventional planar electrode configuration to a three-dimensional stepped structure. The buffer layer is formed with multiple height levels (first height and second height), creating vertical dimensionality that allows electrodes to be positioned at different heights. This dimensional change enables the electrodes to be closer to the optical waveguide while maintaining adequate buffer layer coverage, thus resolving the tradeoff between scattering loss reduction and electric field efficiency.
Solution Approach 2:
The buffer layer is designed with non-uniform thickness, having different heights in different regions. The first buffer layer portion has a first height and the second buffer layer portion has a second height, creating local variations in buffer layer thickness. This local quality differentiation allows the structure to provide both scattering loss reduction (through adequate buffer coverage) and electric field efficiency (through localized thinning near electrodes).
2Volume of moving object
If the device size is reduced to meet demand for smaller optical devices, then device size is reduced, but manufacturing complexity increases
Solution Approach 1:
The buffer layer is segmented into multiple portions with different heights (first buffer layer portion and second buffer layer portion). This segmentation allows the structure to achieve compact dimensions while maintaining functional performance through the differentiated height regions, rather than requiring a uniformly large structure.
Solution Approach 2:
The electrode is nested within the stepped buffer layer structure, with the electrode positioned to extend over the boundary between the first and second buffer layer portions. This nesting arrangement allows compact integration of multiple components (buffer layer and electrode) in a vertically stacked configuration, reducing overall device footprint while maintaining functionality.
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 allows for a compact optical modulator with low scattering loss and high electric field efficiency, addressing the previous tradeoff and enabling size reduction while maintaining performance.
Implementation Method 1
a thin-film LN layer containing an X-cut lithium niobate... electrodes provided, respectively, at a first side and a second side of the optical waveguide
Data Source
AI summary
An optical waveguide device has a substrate, an intermediate layer, a thin-film LN layer containing an X-cut lithium niobate, and a buffer layer stacked on the substrate, and an optical waveguide having a ridge shape formed in the thin-film LN layer. The optical waveguide device includes a plurality of electrodes provided, respectively, at a first side and a second side of the optical waveguide. The electrodes are disposed so that respective bottom surfaces thereof are at positions lower than a position of a surface of the buffer layer.