Semiconductor MZM GSSG Electrode Crosstalk Reduction
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Solution Overview
Problem
Conventional semiconductor Mach-Zehnder optical modulators face challenges with crosstalk between polarization multiplexing-type I/Q modulators, limiting high-speed modulation capabilities due to impedance and speed mismatch between electrical and optical signals, and requiring a two-chip configuration to mitigate crosstalk issues.
Innovation Solution
The semiconductor Mach-Zehnder modulator employs a capacity loading structure with a GSSG differential line configuration, featuring parallel signal and ground electrodes with discrete phase modulation electrodes and connection wiring to achieve impedance and speed matching, reducing crosstalk and enabling high-bandwidth modulation on a single chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional semiconductor MZM with coplanar strip lines is used, then the structure is simple and easy to manufacture, but crosstalk occurs between polarization multiplexing-type I/Q modulators and impedance/speed mismatch limits high-speed modulation
Solution Approach 1:
The patent introduces a ground electrode as an intermediary element between signal electrodes to provide electromagnetic shielding and reduce crosstalk. The ground electrode acts as a mediator that absorbs and redirects electromagnetic interference, preventing it from affecting adjacent modulators while maintaining impedance matching for high-speed operation.
Solution Approach 2:
The patent transitions from a two-dimensional coplanar strip line configuration to a three-dimensional electrode structure by adding ground electrodes positioned at different heights and orientations. This dimensional change enables electromagnetic shielding without increasing the lateral footprint, thus reducing crosstalk while maintaining compact integration.
2Object-affected harmful factors
If two-chip configuration is used to mitigate crosstalk, then crosstalk is reduced, but device complexity and size increase
Solution Approach 1:
The patent merges multiple I/Q modulators onto a single chip by implementing a differential electrode structure with ground electrodes that provide electromagnetic shielding between adjacent modulators. This combining approach maintains low crosstalk levels while simplifying the overall system architecture by eliminating the need for separate chips.
Solution Approach 2:
The patent segments the electrode structure into signal electrodes and ground electrodes with distinct functional roles. The ground electrodes are strategically positioned to create electromagnetic isolation zones between adjacent modulators, enabling single-chip integration with minimal crosstalk by dividing the electromagnetic environment into isolated segments.
3Productivity
If conventional electrode structure is used, then manufacturing is simple, but impedance and speed mismatch between electrical and optical signals limits modulation bandwidth
Solution Approach 1:
The patent optimizes the geometric parameters of the differential electrode structure, including electrode width, spacing, and ground electrode positioning, to achieve impedance matching. By carefully adjusting these physical parameters, the structure achieves both impedance compatibility for high-speed electrical signals and synchronization with optical signal propagation, enabling enhanced modulation bandwidth.
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 achieves stable differential transmission characteristics with high bandwidth, reducing crosstalk and enabling efficient high-speed modulation by matching electrical and optical signal speeds, thus allowing for a compact and cost-effective single-chip integration of polarization multiplexing I/Q modulators.
Implementation Method 1
a voltage can be applied to the first and second arm waveguides 104 and 105 to thereby cause a change of the refractive index due to an electrooptic effect in a semiconductor core layer of the first and second arm waveguides 104 and 105
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A semiconductor MZM of the present invention includes the first and second signal electrodes formed to be parallel to the first and second arm waveguides, respectively; the first and second phase modulation electrodes that are branched from the first and second signal electrodes and that are provided on the first and second arm waveguides in a discrete manner along the first and second signal electrodes; the first and second ground electrodes formed parallelly along the first and second signal electrodes; and a plurality of connection wirings to connect the first and second ground electrodes between a plurality of points. A differential signal is inputted to or outputted from the first and second signal electrodes. The plurality of connection wirings adjacent to each other are arranged with an interval 1/4 times smaller than wavelength of a signal propagated through the first and second signal electrodes.