Folded Optical Modulator Layout to Prevent Field Cancellation
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Solution Overview
Problem
The modulation efficiency of optical modulators with folded structures is compromised due to electric field cancellation and phase changes in opposite directions in the outward and return paths, leading to decreased performance.
Innovation Solution
The optical modulator employs a substrate with mounted chips having orthogonal crystal axes and electrodes arranged to apply electric fields in alignment with the crystal axes, using a folded waveguide structure to maintain consistent modulation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a folded waveguide structure is used to reduce device size, then the area of the optical modulator is reduced, but the modulation efficiency deteriorates due to electric field cancellation between outward and return paths
Solution Approach 1:
The optical modulator is divided into two separate chips: a first chip containing the outward path waveguide and a second chip containing the return path waveguide. This segmentation allows independent optimization of each path's electrode configuration, preventing electric field cancellation by ensuring that each chip's electrodes generate fields in the same direction along their respective crystal axes, thereby maintaining high modulation efficiency while achieving compact integration through chip stacking or side-by-side arrangement.
Solution Approach 2:
The patent transitions from a planar folded structure to a three-dimensional configuration by mounting separate chips in different spatial locations (e.g., stacked vertically or arranged in adjacent planes). This dimensional change allows the outward and return paths to coexist without overlapping in the same plane, eliminating the need for one path to be reflected back on itself, thereby preventing phase inversion and electric field cancellation while maintaining compact overall footprint.
2Device complexity
If electrodes are arranged to apply electric fields in opposite directions for folded waveguide operation, then the waveguide structure can be folded back, but the electric fields cancel each other out reducing modulation efficiency
Solution Approach 1:
The electrode system is segmented into two independent sets: first electrodes on the first chip for the outward path, and second electrodes on the second chip for the return path. Each electrode set is independently configured to generate electric fields aligned with its respective chip's crystal axis in the direction of light propagation. This segmentation eliminates the need for opposing field directions, as each path's electrodes work independently without cancellation, while still enabling the folded waveguide configuration for compactness.
Solution Approach 2:
Each chip is designed with local optimization: the first chip's crystal axis and first electrodes are configured specifically for the outward path, while the second chip's crystal axis and second electrodes are configured for the return path. This local quality approach allows each segment to have the optimal electrode-crystal alignment for its specific function, ensuring high modulation efficiency in both paths without requiring global symmetry that would cause field cancellation.
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 enhances modulation efficiency by aligning electric fields with crystal axes, reducing cancellation effects and maintaining performance in folded waveguide structures.
Implementation Method 1
an electro-optic crystal layer 103 that is laminated on the lower part clad 102, that is formed of a material made of a LN (LiNbO3), or the like, and that has an electro-optical effect
Data Source
AI summary
An optical device includes a substrate, an optical waveguide, and a first chip and a second chip each of which is mounted on the substrate, includes a material having an electro-optical effect that is higher than that of the substrate, and includes a crystal axis in which the strongest electro-optical effect is exerted. The first chip includes a first electrode that is arranged in the vicinity of an input side first waveguide, and that applies an electric field flowing in the same direction as an orientation of the crystal axis of the first chip to the input side first waveguide. The second chip includes a second electrode that is arranged in the vicinity of an output side first waveguide, and that applies an electric field flowing in the same direction as an orientation of the crystal axis of the second chip to the output side first waveguide.