Silicon optical phase shifter with a series of P—N junctions
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Solution Overview
Problem
Si optical phase shifters suffer from capacitance issues at higher frequencies, limiting their use in high-speed or super high-speed applications.
Innovation Solution
A Si optical phase shifter with a series of lateral p-n junctions, where at least two junctions are reverse-biased and one is forward-biased, reducing overall capacitance while maintaining modulation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional Si optical phase shifter is used, then the device structure is simple, but the capacitance is high which limits operation at higher frequencies
Solution Approach 1:
The optical phase shifter is divided into multiple sections, each containing a p-n junction. By segmenting the continuous structure into discrete units with alternating p-type and n-type regions, the total capacitance is reduced while maintaining the phase shifting function across the optical waveguide.
Solution Approach 2:
Different regions of the optical phase shifter are doped with different types (p-type or n-type) to create localized electrical properties. This alternating doping pattern creates regions with different carrier concentrations, enabling carrier depletion in reverse-biased junctions and reducing overall capacitance while maintaining modulation efficiency.
2Speed
If multiple p-n junctions are introduced to reduce capacitance, then the operating frequency increases, but the device complexity increases
Solution Approach 1:
The electrical control function and optical modulation function are merged into a single integrated structure. The p-n junctions are formed directly within the optical waveguide core, combining the electrical depletion region control with the optical confinement, thereby reducing the need for separate control mechanisms and minimizing overall device complexity.
Solution Approach 2:
The alternating p-n junction structure serves multiple functions simultaneously: it provides carrier depletion for phase modulation, reduces overall capacitance for high-frequency operation, and maintains optical confinement within the waveguide. This multi-functionality reduces the need for additional components and simplifies the overall device architecture.
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 solution enables high-frequency operation with similar modulation efficiency and optical loss, suitable for high-speed or super high-speed applications.
Implementation Method 1
The plasma/carrier dispersion effect (e.g., carrier depletion) generates an optical phase shift in light traveling along the Si optical waveguide.
Data Source
AI summary
An apparatus includes a silicon (Si) optical phase shifter. In an embodiment, the optical phase shifter comprises a planar optical waveguide having a silicon optical core, and a pair of biasing electrodes located along opposite sides of a segment of the silicon optical core. The segment of the silicon optical core comprises a series of p-n junctions. The series extends in a direction transverse to an optical propagation direction in a segment of the planar optical waveguide including the segment of the silicon optical core. At least two of the p-n junctions are configured to be reverse biased by applying a voltage across the biasing electrodes.