Mach-Zehnder Optical Modulator Via Hole Electrode Design
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Solution Overview
Problem
Mach-Zehnder type optical modulators face challenges in reducing size due to the presence of T-shaped electrodes, which increase the size of the modulator, and complex electrode shapes, making it difficult to achieve impedance and refractive index matching.
Innovation Solution
The design incorporates a clad layer with via holes along the optical waveguide, allowing for wider and longer travelling wave electrodes connected through these holes, eliminating T-shaped electrodes and simplifying the structure, thereby reducing the modulator's size and facilitating impedance and refractive index matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If T-shaped electrodes are used to connect travelling wave electrode and optical waveguide, then electrical connection is achieved, but the modulator size increases
Solution Approach 1:
The electrode structure is segmented into multiple components: a straight travelling wave electrode, separate via holes for electrical connection, and distinct T-shaped electrodes. This segmentation allows each component to be optimized independently, reducing the overall footprint while maintaining electrical connectivity between the travelling wave electrode and optical waveguide.
Solution Approach 2:
The electrical connection is achieved by transitioning to a vertical dimension through via holes that penetrate the substrate, rather than extending horizontally. This dimensional change allows the T-shaped electrodes to connect to the travelling wave electrode through the thickness of the substrate, significantly reducing the planar area required for connection.
2Reliability
If complex electrode shapes are used to achieve electrical connection, then connection reliability is improved, but device complexity increases
Solution Approach 1:
The electrode system is divided into distinct functional segments: the travelling wave electrode for signal transmission, via holes for vertical electrical connection, and T-shaped electrodes for interfacing with the optical waveguide. This segmentation simplifies the design and fabrication of each component while ensuring reliable electrical connection through standardized interfaces.
Solution Approach 2:
The via holes serve as intermediary elements that facilitate electrical connection between the travelling wave electrode and the T-shaped electrodes. These via holes act as mediators that simplify the connection process by providing a straightforward vertical pathway for electrical signals, reducing the complexity of direct lateral connections.
3Manufacturing precision
If capacitance of optical waveguide is increased to adjust impedance, then impedance matching is achieved, but modulation bandwidth is reduced
Solution Approach 1:
The capacitance distribution is made non-uniform by strategically positioning T-shaped electrodes at specific locations along the optical waveguide. This local quality approach allows impedance matching to be achieved in specific critical regions without increasing the total capacitance, thereby maintaining high modulation bandwidth while achieving the required impedance characteristics.
Solution Approach 2:
The impedance characteristics are adjusted by changing the geometric parameters of the T-shaped electrodes, such as their width, length, and spacing, rather than increasing the overall capacitance of the optical waveguide. This parameter optimization allows impedance matching to be achieved while keeping the total capacitance low, preserving high-speed modulation performance.
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 size of the optical modulator, enhances modulation efficiency, and simplifies the fabrication process while achieving high-frequency refractive index matching and impedance matching, leading to increased modulation band and reduced power consumption.
Implementation Method 1
A Mach-Zehnder type optical modulator of group IV semiconductor includes an optical waveguide in which a core layer of group IV semiconductor is provided on a semiconductor substrate, a travelling wave electrode, and a periodic insulating structure
Data Source
AI summary
It is an object of the present invention to provide a technique for making it possible to reduce the size of a Mach-Zehnder type optical modulator. In a clad layer, provided are a plurality of first and second via holes along an optical waveguide. The Mach-Zehnder type optical modulator includes a first travelling wave electrode connected to a first semiconductor region through the plurality of first via holes, extending along the optical waveguide in a plan view to have a width which is wider and a length and a second travelling wave electrode connected to a second semiconductor region through the plurality of second via holes, extending along the optical waveguide in a plan view to have a width which is wider and a length.