Optical Modulator Coplanar Electrodes Reduce Vpi Voltage
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Solution Overview
Problem
Mach-Zehnder optical devices using PLZT crystals face inefficiencies due to increased distance between electrodes and the crystal, resulting in reduced electric field strength and higher Vπ voltage required for optical modulation.
Innovation Solution
An optical device with a substrate, dielectric film, and insulating film, featuring coplanar electrodes and auxiliary electrodes that apply bias voltages directly to the optical waveguides, allowing for efficient electric field application and reduced Vπ voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating film is formed between the electrode and the PLZT crystal, then the electrode structure is stabilized and insulation is improved, but the distance between the electrode and the crystal increases, reducing electric field strength and increasing Vπ voltage
Solution Approach 1:
The electrode structure is segmented into two parts: a first electrode formed on the PLZT crystal surface and a second electrode formed on the insulating film surface. This segmentation allows the insulating film to provide stabilization and insulation while the separated electrodes maintain effective electric field coupling to the waveguide through the first electrode's direct contact with the crystal.
Solution Approach 2:
The first electrode acts as an intermediary between the second electrode and the PLZT crystal. It transfers the electric field from the second electrode to the crystal without requiring direct contact between the insulating film and the crystal, thus maintaining insulation while preserving electric field strength.
2Reliability
If the distance between the electrode and the PLZT crystal is increased, then the insulating film provides better insulation, but the electric field generated does not effectively reach the waveguide, increasing Vπ voltage
Solution Approach 1:
The electrode system is divided into a first electrode直接接触 the PLZT crystal and a second electrode on the insulating film. This segmentation allows the insulating film to provide insulation while the first electrode ensures direct electric field coupling to the waveguide, maintaining modulation efficiency.
Solution Approach 2:
The first electrode serves as an intermediary that bridges the gap between the insulating film and the PLZT crystal. It enables effective electric field transmission to the waveguide while allowing the insulating film to maintain its insulation function.
3Force
If auxiliary electrodes are formed within the insulating film, then the electric field application is improved without increasing insulating film thickness, but the device structure becomes more complex
Solution Approach 1:
The first and second electrodes are nested within the insulating film structure. The first electrode is formed on the PLZT crystal surface, and the second electrode is formed on the insulating film surface, creating a nested configuration that improves electric field application while utilizing the existing insulating film thickness.
Solution Approach 2:
The electrodes are arranged in a vertical dimension (thickness direction of the insulating film) rather than expanding horizontally. This dimensional approach allows effective electric field application without increasing the lateral footprint or overall device complexity.
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 effective electric field application to optical waveguides, reducing the Vπ voltage by approximately 70% and maintaining high-frequency operation without increasing the thickness of the insulating film, thus enhancing the efficiency of optical modulation.
Implementation Method 1
a Mach-Zehnder optical device is known that uses a lead lanthanum titanium zirconium oxide (a PbLaZrTiO-type complex oxide, shortened hereinafter to 'PLZT') crystal, in which the change in refractive index with respect to applied electric field strength differs from that of LiNbO3 (LN)
Implementation Method 2
forming an insulating film of SiO2 on the PLZT crystal and then forming an electrode
Data Source
AI summary
Provided is an optical modulator that modulates input light with a high frequency and low half-wave voltage. An optical device comprises a substrate; a dielectric film that is formed on the substrate and includes a first optical waveguide and a second optical waveguide that run parallel to each other; an insulating film formed on the dielectric film; a coplanar line that is formed on the insulating film and includes a signal line arranged between the first optical waveguide and the second optical waveguide, a first ground line arranged in a first region, and a second ground line arranged in a second region; and auxiliary electrodes that are arranged in the first region and the second region, are formed in contact with the dielectric film or within the insulating film, and apply bias voltages to the first optical waveguide and the second optical waveguide.