Travelling Wave Electro-Optic Modulator RF Reflection Control
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Solution Overview
Problem
Travelling wave electro-optic modulators face issues with RF wave reflections at the end of electrode strips, leading to adverse effects on device operation and electrical systems, and existing termination methods, such as resistive shunt paths, cause heat dissipation problems and increase manufacturing complexity and cost.
Innovation Solution
A travelling wave electro-optic modulator with a matched termination comprising a serpentine metallic strip and a semiconductive backplane matching element, which are capacitively coupled, providing a distributed heat dissipation and eliminating the need for external components, thus avoiding RF discontinuities and reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistive shunt path is used to terminate electrode strips, then RF reflections are reduced, but heat dissipation problems occur and manufacturing complexity increases
Solution Approach 1:
The patent extracts the resistive termination function from external components and integrates it into the substrate through a serpentine metallic strip pattern. This eliminates the need for external resistors and wire bonding, reducing manufacturing complexity while maintaining RF reflection control.
Solution Approach 2:
The patent merges the termination function with the substrate structure by creating a serpentine metallic strip that is directly patterned on the substrate. This combines the electrical termination function with the mechanical support structure, eliminating separate components and reducing manufacturing steps.
2Reliability
If a resistive element is integrated into the modulator, then RF reflections are controlled, but heat dissipation destabilizes the electro-optic modulator operation
Solution Approach 1:
The patent transitions from a point-contact resistive termination to an extended serpentine pattern distributed across the substrate surface. This dimensional expansion distributes the heat generation from a concentrated point to a distributed area, improving thermal management while maintaining RF termination functionality.
Solution Approach 2:
The serpentine metallic strip pattern creates localized regions of different electrical and thermal properties throughout the substrate. The meandering path provides continuous RF termination while distributing heat generation across multiple locations, allowing different zones to serve different functions.
3Reliability
If external resistive elements are wire bonded to electrode strips, then termination is achieved, but RF discontinuities cause reflections that rise with frequency
Solution Approach 1:
The patent merges the termination structure with the substrate and electrode strips by using a serpentine metallic strip that is directly patterned and bonded to the same substrate. This eliminates the wire bonding interface and associated RF discontinuities, maintaining consistent impedance across the entire structure.
Solution Approach 2:
The termination is segmented into multiple sections along the serpentine path, distributed along the length of the electrode strips. This segmentation allows the termination function to be distributed rather than concentrated at a single point, reducing localized RF discontinuities and improving high-frequency 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
The solution effectively reduces RF reflections and heat dissipation issues, simplifies manufacturing, and integrates the termination within the modulator without additional costs or complexity, enhancing the performance and reliability of the electro-optic modulator.
Implementation Method 1
the serpentine metallic strip and backplane matching element being capacitively coupled together with the backplane matching element being further capacitively coupled to the electrode strips
Implementation Method 2
a first end of each of the first, second and third electrode strips is connected to an RF source and, a second opposite end of each of the first, second and third electrode strips is connected to a matched termination
Data Source
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AI summary
A travelling wave electro-optic modulator comprising a substrate; first and second parallel spaced apart electrode strips arranged on the substrate; first and second optical waveguides arranged on the substrate, the optical waveguides being positioned between the first and second electrode strips and extending parallel thereto; the first electrode strip comprising at least one portion extending proximate to the first optical waveguide; the second electrode strip comprising at least one portion extending proximate to the second optical waveguide; a semiconductive backplane layer arranged within the substrate and extending between the waveguides; and, a matched termination connected to the first and second electrode strips, the matched termination comprising (a) a serpentine electrically conductive strip arranged on the substrate and connecting the first and second electrode strips together; and, (b) a semiconductive backplane matching element, the backplane matching element comprising a plurality of semiconductive backplane plates connected together by at least one semiconductive backplane arm, the plates and at least one backplane arm being arranged within the substrate, the plates being arranged proximate to the electrode strips such that each electrode strip is capacitively coupled to at least one backplane plate; the serpentine electrically conductive strip being arranged such that at least a portion of its length is proximate to at least one backplane arm such that the two are electrically coupled together.