Electro-optical Phase Modulator With Stacked Semiconductor Strips
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Solution Overview
Problem
Existing electro-optical phase modulators have limitations in electro-optical conversion efficiency and electric power consumption, as they require higher control voltages to achieve phase shifts in optical beams.
Innovation Solution
The design incorporates a stack of doped semiconductor strips with dielectric interface layers, where the strips are coupled to different voltage nodes and extended laterally with thinner regions for improved carrier modulation, enhancing the effective optical index modulation and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional capacitive modulator with two silicon strips is used, then the device structure is simple, but the electro-optical conversion efficiency is low requiring higher control voltages
Solution Approach 1:
The patent divides the single capacitive structure into three separate capacitive units arranged in series along the waveguide. Each capacitor is formed by alternating doped silicon strips (first, second, and third strips with opposite conductivity types) separated by dielectric interface layers. This segmentation allows independent optimization of each capacitor's contribution to the overall phase modulation, achieving better electro-optical conversion efficiency while maintaining structural manufacturability.
Solution Approach 2:
The patent transitions from a conventional two-strip planar configuration to a three-dimensional stacked structure with capacitors arranged along the waveguide length. The first and third strips are positioned at different longitudinal locations with the second strip between them, creating a distributed capacitive structure that enhances the effective optical index modulation through multi-dimensional spatial arrangement.
2Measurement precision
If higher control voltages are applied to achieve phase shifts, then the phase modulation depth increases, but the electric power consumption increases
Solution Approach 1:
The patent optimizes the electrical and optical parameters of the three-strip structure, including the doping concentrations of the silicon strips, the thickness and material composition of the dielectric interface layers, and the relative positioning of the strips. These parameter optimizations enable achieving the required phase shift with lower control voltages, thereby reducing electric power consumption while maintaining phase modulation precision.
Solution Approach 2:
The patent employs composite material structures combining doped silicon strips with dielectric interface layers (such as silicon oxide or silicon nitride). The dielectric layers serve dual functions: electrically isolating the opposite-conductivity-type strips while optically confining the light beam within the waveguide. This composite structure enhances the electro-optical interaction efficiency, enabling lower voltage operation.
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 achieves better electro-optical conversion efficiency by applying lower control voltages to achieve phase shifts, specifically by efficiently modulating free carrier density within the waveguide, particularly near the strip surfaces.
Implementation Method 1
The density of free carriers in the two silicon strips is modulated by applying a potential difference between the two strips. This results in a modification of the effective optical index of the waveguide, and thus in a phase shift of the laser light beam according to the applied voltage.
Data Source
AI summary
An electro-optical phase modulator includes a waveguide made from a stack of strips. The stack includes a first strip made of a doped semiconductor material of a first conductivity type, a second strip made of a conductive material or of a doped semiconductor material of a second conductivity type, and a third strip made of a doped semiconductor material of the first conductivity type. The second strip is separated from the first strip by a first interface layer made of a dielectric material, and the third strip is separated from the second strip by a second interface layer made of a dielectric material.