Optical Modulator Bias Control via Surface Acoustic Wave Suppression
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Solution Overview
Problem
In optical modulators with multiple bias electrodes, unstable bias control operations occur due to surface acoustic waves propagating between electrodes on an LN substrate, affecting phase adjustment and temperature drift compensation, leading to detection errors in photo detectors monitoring emission light beams.
Innovation Solution
Incorporating a suppressing unit, such as a metallic film or resin, between the bias electrodes and photo detectors to absorb or block surface acoustic waves, thereby reducing interference and detection errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple bias electrodes are used for phase adjustment and temperature drift compensation, then modulation characteristics can be maintained in a satisfactory manner, but surface acoustic waves propagate between electrodes causing unstable bias control operations and detection errors
Solution Approach 1:
A ground electrode is introduced as an intermediary element between the bias electrodes and photo detectors. This ground electrode acts as a mediator that blocks surface acoustic waves from propagating from the bias electrodes to the photo detectors, while still allowing the bias electrodes to function normally for phase adjustment and temperature drift compensation. The ground electrode serves as a protective barrier that eliminates the harmful interference without affecting the useful functions.
2Device complexity
If bias electrodes are placed close to photo detectors on the same substrate, then device integration is improved, but surface acoustic waves cause detection errors in the photo detectors
Solution Approach 1:
The ground electrode serves as a protective barrier positioned between the bias electrodes and photo detectors. It allows the photo detectors to be integrated close to the bias electrodes on the same substrate, maintaining high device integration, while simultaneously blocking surface acoustic waves from reaching the photo detectors, thus preserving detection accuracy.
Solution Approach 2:
The harmful surface acoustic wave interference is extracted and isolated from the photo detector region by introducing the ground electrode. The ground electrode captures and dissipates the surface acoustic waves before they can reach the photo detectors, effectively removing the interference from the detection path while maintaining the integrated layout.
3Reliability
If a suppressing unit is added to block surface acoustic waves, then bias control stability is improved, but device structure becomes more complex
Solution Approach 1:
The ground electrode is designed to serve multiple functions simultaneously: it provides electrical grounding for the bias electrodes, blocks surface acoustic waves from reaching photo detectors, and maintains the structural integrity of the device. By making the ground electrode multi-functional, the solution achieves bias control stability without significantly increasing device complexity, as the same element performs multiple roles.
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
Stabilizes bias control operations and maintains transmission quality by effectively suppressing surface acoustic waves and minimizing detection errors in optical modulators with multiple bias electrodes.
Implementation Method 1
unstable bias control operations occur due to surface acoustic waves propagating between electrodes on an LN substrate
Implementation Method 2
Incorporating a suppressing unit, such as a metallic film or resin, between the bias electrodes and photo detectors to absorb or block surface acoustic waves
Implementation Method 3
a substrate having a piezoelectric effect
Data Source
AI summary
To perform a stable bias control by improving detection accuracy of intensity of an dither signal component, which is detected by a photo detector, in an optical modulator including a bias electrode to which a dither signal is applied, and a photo detector that monitors an optical signal propagating through the inside of an optical waveguide in the same substrate. The optical modulator includes: a substrate having a piezoelectric effect (102); an optical waveguide (116a or the like) that is formed on the substrate; a bias electrode (158a or the like) that controls an optical wave that propagates through the optical waveguide; and a photo detector (168a or the like) that is formed on the substrate, and monitors an optical signal that propagates along the optical waveguide. At least one suppressing unit (190 or the like), which suppresses a surface acoustic wave that propagates from the bias electrode to the photo detector, is disposed between a region in which the bias electrode is formed and a portion in which the photo detector is disposed on the substrate.