Differential Optical Modulator Layout for Low-Voltage Wide Bandwidth
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Solution Overview
Problem
Optical modulators face challenges in achieving low electrode and optical losses, large modulation bandwidth, and efficient operation at low driving voltages due to electrode signal losses and increased voltage requirements with frequency, particularly in high-frequency applications.
Innovation Solution
The use of a ferroelectric nonlinear optical modulator interface with differential electrode pairs and ground connections, coupled with a differential driver, allows for low-voltage phase shifts and reduced signal losses, utilizing materials like lithium niobate and lithium tantalate, and optimized waveguide and electrode configurations to minimize losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional optical modulators are used to achieve sufficient optical modulation, then the modulation depth is improved, but the electrode driving voltage increases and area consumption increases
Solution Approach 1:
The patent divides the modulator into multiple sections with interleaved electrodes, where each section contributes to the overall modulation. This segmentation allows the electric field to be distributed across multiple smaller regions, achieving sufficient total modulation depth while maintaining lower driving voltages compared to a single large electrode structure.
Solution Approach 2:
The patent employs interleaved electrode configurations where electrodes are positioned at different locations (e.g., top and bottom surfaces) to create localized electric field regions. This local quality approach optimizes the electric field distribution in specific areas, enhancing modulation efficiency at lower voltages by concentrating the field where it is most effective.
2Loss of energy
If electrode length is increased to reduce microwave losses, then electrode losses are improved, but device area increases
Solution Approach 1:
The patent transitions from a single-plane electrode layout to a three-dimensional interleaved configuration with electrodes on both top and bottom surfaces. This dimensional change allows microwave signals to travel through multiple parallel paths, effectively reducing losses without requiring a larger footprint area, as the length reduction is compensated by the added vertical dimension.
Solution Approach 2:
The patent combines multiple electrode pairs in an interleaved arrangement where top and bottom electrodes work together to achieve the desired modulation. This merging of multiple electrode structures into a compact integrated configuration reduces total microwave loss by providing redundant signal paths while maintaining a small device area.
3Productivity
If operating frequency is increased to achieve larger modulation bandwidth, then bandwidth is improved, but electrode losses increase and required driving voltage increases
Solution Approach 1:
The patent segments the electrode structure into multiple interleaved pairs that can operate effectively at high frequencies. This segmentation reduces the inductance and capacitance of individual electrode sections, allowing the modulator to maintain low losses and acceptable driving voltages even at elevated operating frequencies with larger bandwidth.
4Manufacturing precision
If electrode length is increased to achieve larger modulation, then modulation depth is improved, but optical losses increase
Solution Approach 1:
The patent utilizes three-dimensional interleaved electrode positioning with electrodes on both top and bottom surfaces of the waveguide. This dimensional arrangement achieves sufficient modulation depth through the combined effect of multiple shorter electrode sections rather than relying on a single long electrode, thereby reducing the interaction length and associated optical losses while maintaining effective modulation.
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 enables low-voltage operation with reduced electrode and optical losses, enabling efficient modulation across a wide frequency range, achieving phase shifts of π with voltages as low as 1-2 volts and minimizing device area consumption.
Implementation Method 1
An optical modulator typically includes one or more waveguides formed using materials having an index of refraction that is sensitive to electric fields. The waveguide(s) carry an optical signal. The modulator also includes electrodes that apply an electric field to the waveguide to alter the index of refraction of the waveguide.
Implementation Method 2
The waveguide(s) are formed of a ferroelectric nonlinear optical material. The application of an electrode signal alters an index of refraction of the waveguide material, thereby modulating the optical signal carried by the waveguide(s).
Data Source
AI summary
An interface for an optical modulator and the optical modulator are described. The interface includes first and second differential line pairs. The first differential line pair has a first negative line and a first positive line arranged on opposing sides of a first waveguide. The first negative line is on a distal side of the first waveguide relative to a second waveguide. The first positive line is on a proximal side of the first waveguide relative to the second waveguide. The second differential line pair has a second negative line and a second positive line arranged on opposing sides of the second waveguide. The second negative line is on a distal side of the second waveguide relative to the first waveguide. The second positive line is on a proximal side of the second waveguide relative to the first waveguide. The first and second waveguides each include lithium niobate and/or lithium tantalate.