Oxide Capacitor Electro-Optical Phase Shifter Design
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Solution Overview
Problem
Existing electro-optical phase shifters face a challenge in achieving a balance between high sensitivity and low optical losses, as increasing sensitivity often results in higher optical losses due to higher doping levels.
Innovation Solution
The electro-optical phase shifter incorporates an oxide capacitor structure with a semiconductor material, featuring a conductive layer and insulating layer configuration that increases capacitance without increasing optical losses, using shallow trench isolation techniques and doping gradients to optimize sensitivity and response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the doping level of the waveguide area is increased to improve sensitivity, then the sensitivity increases, but the optical losses increase
Solution Approach 1:
The invention divides the control structure into two separate wings (first wing and second wing) positioned on opposite sides of the waveguide rib. Each wing is independently doped and controlled, allowing the optical field to interact with both wings while maintaining lower doping levels in each individual wing compared to a single high-doping configuration. This segmentation enables achieving sufficient sensitivity through combined effect while reducing optical losses in each segment.
Solution Approach 2:
The invention applies different doping levels to different regions: the first and second wings have doping levels optimized for electro-optical interaction, while the central waveguide rib maintains a doping level optimized for low optical loss. This local differentiation allows each region to perform its optimal function - the wings provide sensitivity through carrier modulation, while the rib minimizes optical attenuation.
2Ease of operation
If a PN junction structure is used to control phase shift, then the phase modulation capability is achieved, but the device complexity increases compared to simpler structures
Solution Approach 1:
The invention extracts the essential phase modulation function from a traditional PN junction structure and implements it using two independently controlled doped wings. Instead of requiring a complex PN junction with its associated depletion region dynamics and potential carrier injection complications, the design uses two simpler doped regions that can be independently biased to achieve the desired phase shift, simplifying the overall device architecture while maintaining functionality.
Solution Approach 2:
Rather than using a single PN junction where P and N regions are intimately coupled requiring precise junction formation, the invention inverts the approach by using two separately doped wings of the same conductivity type (or different types) that are spatially separated and independently controlled. This inversion allows for more flexible fabrication and simpler device operation while achieving the same phase modulation objective.
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 sensitivity while minimizing optical losses, allowing for a higher capacitance value than traditional junction capacitance, thus achieving a better compromise between sensitivity and optical loss, with the oxide capacitor providing a more efficient phase shift response.
Implementation Method 1
a control structure configured to modify the concentration of carriers in the rib according to a control voltage present between first and second control terminals of the phase shifter
Implementation Method 2
The sensitivity of the electro-optical phase shifter depends on the capacitance CJ of the junction 14
Data Source
AI summary
An electro-optical phase shifter to be located in an optical waveguide may include a rib of a semiconductor material extending along a length of the optical waveguide and a control structure configured to modify a concentration of carriers in the rib according to a control voltage present between first and second control terminals of the phase shifter. The control structure may include a conductive layer covering a portion of the rib and electrically connected to a first of the control terminals. An insulating layer may be configured to electrically isolate the conductive layer from the rib.