Dual Static Electro-Optical Phase Shifter for Modulator Matching
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Solution Overview
Problem
Mach-Zehnder interferometer optical modulators face challenges in achieving desired modulation frequencies due to difficulties in optical and electrical matching between dynamic electro-optical phase shifters, primarily caused by fabrication constraints leading to significant gaps between waveguide branches, which hinder precise control and efficient modulation.
Innovation Solution
A dual dynamic phase shifter configuration with two optical action zones in parallel waveguides, where a single modulation voltage is applied between terminals, and a dual static phase shifter design with a P-I-N junction structure, allowing for improved matching and compact modulator architecture by reducing the distance between phase shifters and enabling symmetric control over optical beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate dynamic phase shifters are inserted into separate waveguide branches, then differential modulation can be achieved, but fabrication constraints cause significant gaps between branches making electrical and optical matching difficult
Solution Approach 1:
The patent merges two separate dynamic phase shifters into a single integrated device structure. The combined phase shifter contains two optical action zones within one semiconductor body, allowing both phase modulation functions to be performed in a unified structure rather than in separate waveguide branches, thereby eliminating the matching problems caused by fabrication gaps
Solution Approach 2:
The single semiconductor body is segmented into two distinct optical action zones, each capable of interacting with a separate optical waveguide. This segmentation allows independent control of each zone while maintaining structural integration, enabling differential modulation without requiring separate phase shifter devices
2Volume of moving object
If a single semiconductor body contains two optical action zones, then device compactness is improved, but optical coupling between waveguides must be prevented
Solution Approach 1:
The patent introduces an insulating layer as an intermediary between the two optical action zones within the semiconductor body. This insulating barrier prevents optical coupling between the adjacent waveguides while allowing the phaseshifters to remain in close proximity, thus maintaining compactness without suffering from harmful optical interference
Solution Approach 2:
The semiconductor structure exhibits different local properties: the optical action zones are designed with specific doping levels and geometries optimized for phase modulation, while the insulating regions between them provide optical isolation. This local differentiation allows simultaneous achievement of compact integration and optical separation
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 dual phase shifter configuration ensures effective differential modulation and optical coupling prevention, achieving better electrical and optical matching, thus enhancing modulation frequency and modulator compactness while simplifying control signals.
Implementation Method 1
A P-doped zone extends to the left of junction 14... An N-doped zone extends to the right of the junction 14... This configuration causes a displacement of electrons e from the N region to the cathode and of holes h from the P region to the anode, and the creation of a depletion region D in the vicinity of the junction 14. The carrier concentration is thus based upon the magnitude of the bias voltage in the area crossed by the optical beam, which results in a corresponding modification of the refractive index of this area.
Implementation Method 2
The modulator includes an optical waveguide receiving an optical signal with power Pin, which is divided into two branches 12a and 12b at a point S. The two branches come together again at a point J.
Data Source
AI summary
A semiconductor electro-optical phase shifter comprises a central zone (I1, I2) having a minimum doping level; first and second lateral zones (N+, P+) flanking the central zone along a first axis, respectively N and P-doped, so as to form a P-I-N junction between the first and second lateral zones. The central zone comprises first and second optical action zones (I1, I2) separated along the first axis. The second lateral zone is doped discontinuously along a second axis perpendicular to the first axis. Two electrical control terminals (A, C) are provided, one in contact with the first lateral zone, and the other in contact with doped portions of the second lateral zone.