Optical Modulator Stress Relaxation for Temperature Drift
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Solution Overview
Problem
Highly integrated optical modulators experience temperature drift due to stress-induced strain from lead-out wiring, leading to operating point shifts and increased power dissipation, which complicates the symmetry of the control electrode structure and requires larger DC voltages for bias point compensation.
Innovation Solution
The optical modulator incorporates a control electrode with a signal electrode and ground electrode, featuring a stress relaxation structure that is axially symmetrical to the lead-out wiring with respect to the centrosymmetric axis of the Mach-Zehnder type optical waveguide, ensuring that the lead-out wiring is parallel to the extended direction of the waveguide and the ground electrode is configured to compensate for stress-induced strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If lead-out wiring is added to connect the signal electrode to external circuits, then the optical modulator becomes functional and usable, but stress-induced strain occurs on the optical waveguide causing temperature drift
Solution Approach 1:
The patent introduces an asymmetric stress relaxation structure (protrusion or recess) on one side of the optical waveguide to compensate for the asymmetric stress caused by the lead-out wiring. This creates a balanced stress distribution that eliminates temperature drift while maintaining the necessary electrical connectivity.
Solution Approach 2:
The stress relaxation structure is designed in advance to counteract the stress that will be induced by the lead-out wiring. By pre-positioning the protrusion or recess, the patent prevents temperature drift before it occurs, rather than attempting to correct it afterward.
2Ease of operation
If the control electrode structure is made asymmetric to accommodate lead-out wiring, then electrical connectivity is achieved, but temperature drift increases due to unbalanced stress
Solution Approach 1:
The patent deliberately introduces a controlled asymmetry in the form of a stress relaxation structure that counterbalances the asymmetry caused by the lead-out wiring. This creates a symmetric stress distribution pattern that eliminates temperature drift while preserving electrical connectivity.
Solution Approach 2:
The patent converts the harmful asymmetric stress caused by lead-out wiring into a beneficial balanced stress distribution by introducing a compensating stress relaxation structure. The harmful asymmetry is transformed into a balanced state that improves temperature drift characteristics.
3Volume of moving object
If high integration is implemented to reduce device size, then the optical modulator becomes more compact, but temperature drift becomes more severe due to increased stress concentration
Solution Approach 1:
The patent applies a localized stress relaxation structure at the specific location where stress concentration occurs due to high integration. This local modification allows the device to maintain its compact size while eliminating temperature drift at the critical stress point.
Solution Approach 2:
The patent segments the control electrode structure by introducing a distinct stress relaxation feature (protrusion or recess) that is separate from the main electrode function. This segmentation allows independent optimization of stress distribution without affecting the overall device integration.
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
This configuration effectively suppresses temperature drift, reduces the required voltage for bias control, and minimizes operating point shifts, thereby enhancing the long-term operation and reducing power dissipation in the optical modulator.
Implementation Method 1
a substrate having an electro-optic effect, an optical waveguide which is formed on the substrate and provided with at least one Mach-Zehnder type optical waveguide, and a control electrode which controls light waves propagating through the optical waveguide
Data Source
AI summary
Provided is an optical modulator in which even in a case where an optical waveguide and a control electrode are highly integrated, a distortion due to stress acting on the optical waveguide from lead-out wiring of a signal electrode is mitigated and occurrence of a temperature drift or the like is suppressed. An optical modulator includes: a substrate 1 having an electro-optic effect; optical waveguides (L1 to L4), each of which is formed on the substrate and provided with at least one Mach-Zehnder type optical waveguide; and a control electrode which controls light waves propagating through the optical waveguides, in which the control electrode is configured of signal electrodes (S1 and S2) and ground electrodes (G1 to G3), each of the signal electrodes being provided with a pad part (S1P or S2P) for input or output, which is electrically connected to an electric circuit which is provided outside the substrate, an interaction part (indicated by arrow R1) which applies an electric field to the optical waveguide, and a lead-out wiring part which connects the pad part and the interaction part to each other, a portion of the lead-out wiring part is disposed parallel to an extended direction (a lateral direction in FIG. 3) of the Mach-Zehnder type optical waveguide within a range (indicated by arrow R2) in which two branching waveguides configuring the Mach-Zehnder type optical waveguide are present in the extended direction, and any one of a portion of the interaction part, another portion of the lead-out wiring part, and a stress relaxation structure of the ground electrode is formed at a position which is axially symmetrical to the portion of the lead-out wiring part with respect to a centrosymmetric axis in the extended direction of the Mach-Zehnder type optical waveguide.