Rib-Slab Optical Waveguide Asymmetry Reduces Capacitance
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Solution Overview
Problem
Conventional substrate-type optical waveguides with phase modulation function face challenges in reducing high frequency loss without increasing power consumption, as capacitance is directly proportional to carrier densities and voltage requirements.
Innovation Solution
A substrate-type optical waveguide design featuring a rib-slab type core with varying slab widths, where the N-type semiconductor region width differs from the P-type semiconductor region width, reducing lower cladding layer capacitance without decreasing carrier densities, thereby minimizing high frequency loss and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If carrier densities in the P-type semiconductor region and N-type semiconductor region are lowered to decrease depletion layer capacitance, then capacitance decreases, but operating voltage must be increased to control effective refractive index, leading to increased power consumption
Solution Approach 1:
The patent applies asymmetry by making the first slab part wider than the second slab part in the rib-slab type core. This asymmetric structure creates different widths for the N-type semiconductor region and P-type semiconductor region, allowing the depletion layer to be positioned preferentially in one region. This enables capacitance reduction through geometric asymmetry rather than lowering carrier densities, thus avoiding increased operating voltage and power consumption.
Solution Approach 2:
The patent implements local quality by creating regions with different properties within the core structure. The first slab part has a different width than the second slab part, resulting in localized differences in electric field distribution and depletion layer formation. This allows the depletion layer to concentrate in specific regions, reducing overall capacitance without requiring uniform lowering of carrier densities across the entire structure.
2Loss of energy
If conventional symmetric rib-slab type core is used with equal slab widths, then manufacturing is simplified, but capacitance cannot be reduced without lowering carrier densities, which increases operating voltage
Solution Approach 1:
The patent introduces asymmetry in the slab part widths to reduce capacitance. The first slab part is designed with a greater width than the second slab part, which creates an asymmetric electric field distribution and enables the depletion layer to form preferentially in the narrower region. This asymmetric geometry reduces capacitance without requiring complex multi-layer structures or precise carrier density control, maintaining ease of manufacture through standard semiconductor fabrication processes.
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 design effectively decreases capacitance and high frequency loss without increasing power consumption, enhancing the performance of substrate-type optical waveguides and modulators by optimizing the rib-slab structure and electrode configurations.
Implementation Method 1
it is possible to modulate a phase of light propagating through the core by applying a signal voltage between the N-type semiconductor region and the P-type semiconductor region
Implementation Method 2
An effective refractive index of the core is determined in accordance with a size of the depletion layer, and the size of the depletion layer can be changed in accordance with a magnitude of a voltage which is applied
Data Source
AI summary
The substrate-type optical waveguide includes a rib-slab type core. A depletion layer exists in a rib part and, in any cross section of the core, a width of a first slab part is set to be greater than a width of a second slab part.