Optical Modulator Dummy Electrode Symmetry
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Solution Overview
Problem
Optical modulators with X-cut substrates experience degradation of extinction ratio and temperature drift due to feeder electrode asymmetry and absorption of light waves, leading to propagation loss and stress imbalance on optical waveguides.
Innovation Solution
Incorporating dummy electrodes symmetrically positioned relative to feeder electrodes crossing Mach-Zehnder type optical waveguides, with narrower crossing widths and parallel feeder electrode configurations, to equalize propagation loss and maintain symmetry, thereby reducing extinction ratio degradation and temperature drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the feeder electrode is positioned to power the DC electrode, then the DC bias can be applied to the control electrode, but the feeder electrode crosses the optical waveguide and absorbs light waves, causing propagation loss and extinction ratio degradation
Solution Approach 1:
The patent applies asymmetry by introducing a dummy electrode that creates a symmetric structure overall. The dummy electrode is positioned asymmetrically relative to the feeder electrode crossing, but this asymmetric addition balances the total structure to achieve symmetry, thereby reducing light absorption and improving extinction ratio
2Ease of manufacture
If the feeder electrode is positioned asymmetrically due to wiring patterns, then power supply can be implemented, but asymmetry causes different internal stress on optical waveguides, leading to temperature drift and mode field diameter changes
Solution Approach 1:
The patent uses asymmetry as a means to achieve symmetry. The dummy electrode is placed asymmetrically with respect to the feeder electrode, but this asymmetric configuration creates overall symmetry in the electrode structure, balancing internal stresses on the optical waveguides and preventing temperature drift
3Device complexity
If control electrodes are disposed on both sides of the optical waveguide, then no buffer layer is needed, but the feeder electrode must cross the optical waveguide to connect, causing light absorption and propagation loss
Solution Approach 1:
The patent maintains the beneficial configuration of control electrodes on both sides of the optical waveguide without requiring a buffer layer. The dummy electrode is introduced to compensate for the asymmetric light absorption caused by the feeder electrode crossing, creating overall symmetry and reducing propagation loss
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 optical modulator achieves balanced propagation loss and reduced extinction ratio degradation, while suppressing temperature drift by ensuring equal internal stress on optical waveguides through symmetrical dummy electrode placement and configuration.
Implementation Method 1
a substrate having an electro-optic effect, such as lithium niobate (LN), is used
Data Source
AI summary
Provided is an optical modulator in which degradation of an extinction ratio is suppressed and a temperature drift phenomenon is suppressed.An optical modulator includes: a substrate having an electro-optic effect; an optical waveguide formed on the substrate; and a control electrode for controlling light waves propagating through the optical waveguide, in which the optical waveguide has one or more Mach-Zehnder type optical waveguides (A1 to A3 and B1 to B3), the control electrode has DC electrodes (C1 to C4) which apply DC bias, a feeder electrode which feeds DC bias to the DC electrode crosses one of two branched waveguides of the Mach-Zehnder type optical waveguide, and a first dummy electrode (a dotted line E5 or E6) is provided at a specific position on the other one of the two branched waveguides, which is a specific position symmetrical in relation to a position at which the feeder electrode crosses the one of the two branched waveguides.