Semiconductor Optical Modulator Digital Alloy Quantum Well
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Solution Overview
Problem
In semiconductor optical modulators, the use of a single bulk semiconductor layer for the quantum well layer leads to increased propagation loss due to widened exciton absorption wavelength half-width, resulting in smaller changes in absorption coefficient or refractive index.
Innovation Solution
The semiconductor optical modulator employs a digital alloy in the optical modulation layer, where semiconductor layers with different constituent elements or composition ratios are alternately stacked to a thickness of two or more atomic layers, effectively narrowing the exciton absorption wavelength half-width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single bulk semiconductor layer is used for the quantum well layer, then the manufacturing process is simple, but the exciton absorption wavelength half-width is widened causing increased propagation loss
Solution Approach 1:
The patent divides the quantum well layer into multiple thin semiconductor layers (2-10 atomic layers each) with different composition ratios, alternating between layers with higher and lower alloy content. This segmentation narrows the exciton absorption wavelength half-width by creating discrete energy levels, thereby reducing propagation loss while maintaining manufacturing feasibility through controlled layer-by-layer deposition
Solution Approach 2:
The patent creates a composite structure by alternating layers of semiconductor materials with different composition ratios (e.g., InGaAsP layers with varying In and P content) within the quantum well region. This composite approach enables precise control of optical properties, narrowing absorption bandwidth and reducing energy loss during light transmission
2Device complexity
If a single bulk semiconductor layer is used for the quantum well layer, then the device structure is simple, but the change in absorption coefficient or refractive index is reduced
Solution Approach 1:
The patent implements local quality variations by creating layers with different composition ratios at specific positions within the quantum well structure. Each layer pair has optimized local composition to maximize the change in absorption coefficient or refractive index when voltage is applied, thereby enhancing modulation efficiency without requiring complex overall device architecture
Solution Approach 2:
The patent designs the alternating layer structure to dynamically respond to applied voltage, where the discrete energy levels created by the layered structure enable larger and more controllable changes in optical properties. The structure allows for enhanced electro-optic modulation by optimizing the interaction between the electric field and the confined carriers in each layer
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 approach enhances the change in absorption coefficient or refractive index, thereby reducing propagation loss and allowing for more efficient light modulation.
Implementation Method 1
The quantum well has a structure in which a semiconductor layer (quantum well layer) having a small band gap is interposed between barrier layers having a band gap larger than that of the quantum well layer
Implementation Method 2
In the quantum well layer, hole level and electron level are discretely formed, holes and electrons are attracted to each other by Coulomb force to form excitons
Implementation Method 3
when a voltage is applied, electrons and holes move to a low energy side and a high energy side, respectively, in the quantum well layer. Therefore, when the voltage is applied, the optical absorption energy by the excitons becomes smaller than that in the case where the voltage is not applied, and an optical absorption edge wavelength shifts to a long wavelength side. This is called a quantum-confined Stark effect
Data Source
AI summary
A semiconductor optical modulator is formed by stacking a plurality of semiconductor layers including an optical modulation layer on a semiconductor substrate and emits light by modulating an intensity or a phase of light incident on the optical modulation layer. The optical modulation layer is formed using a digital alloy in which the semiconductor layers having a layer thickness of two or more atomic layers and having different constituent elements or composition ratios are alternately and repeatedly stacked.