Electro-Optic Modulator Electrode Short-Circuit Bandwidth
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Solution Overview
Problem
Electro-optic Mach-Zehnder modulators face limitations in high-frequency bandwidth due to electrical and optical velocity mismatch, electrical losses, and impedance mismatching, which are not adequately addressed by existing designs.
Innovation Solution
The modulator incorporates a travelling wave electrode arrangement with a first and second section of waveguide electrodes, where the sections are galvanically separated, and an electrically conductive connecting element creates a short-circuit between the electrodes in the second section, allowing a high-frequency voltage source to maintain different potentials, enhancing electro-optic properties without increasing modulation voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the length of the electrodes is reduced to increase bandwidth, then the electro-optic bandwidth is improved, but a higher modulation voltage is required
Solution Approach 1:
The electrode arrangement is divided into multiple sections (first section with electrodes 21, 22 and second section with electrodes 221, 222) that are galvanically separated. Each section can be independently optimized for different functions: the first section for voltage application and the second section with short-circuit for bandwidth enhancement, resolving the contradiction between bandwidth and voltage requirements
Solution Approach 2:
The invention changes the electrical boundary conditions by introducing short-circuits in the second section, transforming the electrode structure from open-ended to short-circuited. This parameter change enables the electrodes to support higher frequency modes and improves bandwidth without requiring proportional increases in modulation voltage
2Speed
If coplanar travelling wave electrodes are used to induce phase shift, then the modulator can operate at high speeds, but velocity mismatch between electrical and optical signals limits the bandwidth
Solution Approach 1:
The invention makes the electrode system dynamic by introducing frequency-dependent behavior through the short-circuited sections. The electrical line and waveguide electrodes are designed to support travelling waves at specific frequencies, creating a dynamic response that adapts to high-frequency operation and reduces velocity mismatch effects
Solution Approach 2:
The electrical line acts as an intermediary element that couples the voltage source to the waveguide electrodes. This intermediary structure enables better impedance matching and facilitates efficient energy transfer between the electrical and optical domains, mitigating velocity mismatch limitations
3Power
If multiple waveguide electrodes are used to apply voltage across optical waveguides, then the electro-optic effect is enhanced, but impedance mismatching occurs
Solution Approach 1:
Different sections of the electrode arrangement have different electrical characteristics: the first section is designed for voltage application with specific impedance, while the second section with short-circuit is designed for bandwidth enhancement. This local differentiation allows each section to be optimized for its specific function, maintaining impedance matching while enhancing the electro-optic effect
Solution Approach 2:
The short-circuit connections in the second section create equipotential regions between adjacent waveguide electrodes, which helps to equalize the electrical distribution and reduce impedance mismatches that would otherwise occur at electrode transitions or terminations
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 enhances the modulator's high-frequency characteristics by allowing high-frequency signals to interact with optical waveguides effectively, improving bandwidth without requiring higher modulation voltages.
Implementation Method 1
an electro-optic Mach-Zehnder modulator... a first optical waveguide forming a first modulator arm and a second optical waveguide forming a second modulator arm; an electrode arrangement comprising a plurality of first waveguide electrodes for applying a voltage across the first optical waveguide and a plurality of second waveguide electrodes for applying a voltage across the second optical waveguide
Implementation Method 2
at least one electrically conductive connecting element generating a short-circuit between the at least one first waveguide electrode and the at least one second waveguide electrode of the second section
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to an electro-optic modulator, in particular a Mach-Zehnder modulator or an electro-absorption modulator, comprising: - at least one optical waveguide (11, 12); - a travelling-wave electrode arrangement (2, 2000) comprising at least one waveguide electrode (221, 222, 2100) for applying a voltage across the optical waveguide (11, 12) and at least one electrical line (223, 224, 2300, 2400) and/or another waveguide electrode (221, 222), wherein at least one voltage source (41, 4100) is to be connected to the waveguide electrode (221, 222, 2100) and the electrical line (223, 224, 2300, 2400) or the other waveguide electrode (221, 222) in such a way that the potential of the waveguide electrode (221, 222, 2100) is different from the potential of the electrical line (223, 224, 2300, 2400) and the other waveguide electrode (221, 222), respectively; and - at least one electrically conductive connecting element (3, 3a, 3b) generating a short-circuit between the waveguide electrode (221, 222, 2100) and the electrical line (223, 224, 2300, 2400) and/or between the waveguide electrode (221, 222, 2100) and the other waveguide electrode (221, 222). The invention also relates to a method for fabricating an electro-optic modulator.