Distributed Optical Phase Modulator Layout for Low-Voltage Bandwidth
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Solution Overview
Problem
Existing electro-optic modulators face a trade-off between low drive voltage and high modulation bandwidth, limited by group velocity mismatch, walk-off phenomena, and crosstalk, which hinder performance improvements.
Innovation Solution
A distributed optical phase modulator design with a distributed drive electrode and shielding electrodes, minimizing walk-off and crosstalk, and employing synchronized electrical signals across sub-drive electrodes to enhance modulation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional one-section drive electrode is used, then the device structure is simple, but the drive voltage is high and modulation bandwidth is limited
Solution Approach 1:
The drive electrode is divided into multiple sub-drive electrodes arranged in sequence along the optical waveguide. Each sub-drive electrode has a length of 5-20 mm and is spaced 0.5-2 mm apart. This segmentation allows the total interaction length to be achieved through cumulative effect while keeping individual electrode lengths short, reducing the drive voltage required for each section while maintaining overall modulation effectiveness.
2Power
If the drive electrode length is increased to reduce drive voltage, then the drive voltage decreases, but the modulation bandwidth is limited due to walk-off phenomenon
Solution Approach 1:
By segmenting the drive electrode into multiple short sections (5-20 mm each) with small spacing (0.5-2 mm), the patent achieves a long effective interaction length through cumulative modulation effect while maintaining short individual electrode lengths. This prevents the walk-off phenomenon between optical and electrical signals that would occur in a single long electrode, thereby maintaining high modulation bandwidth while reducing drive voltage requirements.
3Power
If multiple sub-drive electrodes are used to reduce drive voltage, then the drive voltage decreases, but crosstalk between electrodes increases
Solution Approach 1:
Grounding electrodes are positioned between adjacent sub-drive electrodes to act as electromagnetic shields. These intermediary grounding structures block capacitive coupling and electromagnetic interference between neighboring driven electrodes, effectively reducing crosstalk while allowing the multi-electrode configuration to maintain low drive voltage operation.
4Manufacturing precision
If the spacing between sub-drive electrodes is increased, then the manufacturing precision requirement is reduced, but the modulation efficiency decreases
Solution Approach 1:
The patent optimizes the spacing parameter between sub-drive electrodes to be 0.5-2 mm, which represents a carefully selected range that balances manufacturing tolerances with modulation efficiency. This parameter optimization ensures that the cumulative modulation effect across multiple electrodes is maximized while maintaining practical manufacturability with standard fabrication tolerances.
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 design achieves reduced drive voltage and increased modulation bandwidth with minimized signal loss and enhanced modulation efficiency.
Implementation Method 1
The electro-optic effect means that, when a voltage is applied to the electro-optic crystal, the refractive index of the electro-optic crystal will be changed, resulting in a change in the characteristics of the light wave passing through the crystal, so as to realize the modulation of the phase, amplitude, intensity and polarization state of the optical signal.
Data Source
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AI summary
Provided is a distributed optical phase modulator, comprising: a substrate (10); an optical waveguide (20) arranged on the substrate (10); a drive electrode (30) that is arranged on the substrate (10) and comprises a plurality of sub drive electrodes (31) arranged at intervals; and at least one shielding electrode (40), wherein at least some shielding electrodes and the sub drive electrodes (31) are arranged at intervals. The optical waveguide (20) sequentially passes through the sub drive electrodes (31) and the shielding electrodes (40). The length of each part of the drive electrode (30) is far less than the total length of an equivalent traditional modulator, and the drive signal voltage of each part is also far less than the drive signal voltage of the equivalent traditional modulator. In each part of the drive electrode (30), the propagation of an optical signal and the propagation of an electrical signal can be approximately synchronous, even synchronous. The phenomenon of walk-off between the optical signal and the electrical signal is minimized, and the upper limit of a modulation bandwidth is improved. The shielding electrodes (40) are respectively arranged between the sub drive electrodes (31), so that crosstalk between the sub drive electrodes (31) can be shielded, and crosstalk between the sub drive electrodes (31) can be greatly reduced.