Optical Modulator Layering for Velocity Mismatch
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Solution Overview
Problem
Conventional optical modulators using high dielectric constant materials like PLZT or BTO face challenges in achieving high modulation efficiency while maintaining a wide operating band due to velocity mismatch between light and electric signals.
Innovation Solution
The optical modulator incorporates an electro-optic layer with a material layer having a lower dielectric constant and a core layer with a higher refractive index than the electro-optic and material layers, which helps in aligning the refractive indices for both electric signals and light, thereby reducing velocity mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high dielectric constant materials like PLZT or BTO are used in the optical modulator, then modulation efficiency is improved, but velocity mismatch between light and electric signals occurs, limiting the operating band
Solution Approach 1:
The optical modulator is divided into multiple functional layers: a first optical waveguide layer, a first electro-optic layer, a first intermediate layer, a second electro-optic layer, and a second optical waveguide layer. This segmentation allows each layer to be optimized for its specific function, enabling high modulation efficiency while maintaining a wide operating band by reducing velocity mismatch through proper layer design and material selection.
Solution Approach 2:
The patent employs composite material structures where electro-optic materials (PLZT or BTO) are combined with intermediate layers having different dielectric constants. This composite approach allows the system to benefit from the high electro-optic coefficient of PLZT/BTO while using the intermediate layers to adjust and match impedance, thereby reducing velocity mismatch and extending the operating band.
2Reliability
If the electro-optic layer uses high dielectric constant material, then the electro-optic coefficient is high, but the velocity mismatch between light and electric signals increases
Solution Approach 1:
Intermediate layers with dielectric constants lower than the electro-optic layers are inserted between the electro-optic layers and the optical waveguide layers. These intermediate layers act as mediators that adjust the electromagnetic field distribution and reduce the velocity mismatch between light and electric signals, while allowing the electro-optic layers to maintain their high electro-optic coefficients.
Solution Approach 2:
The patent changes the dielectric constant parameter by introducing intermediate layers with different dielectric constants (lower than the electro-optic layers). This parameter change allows the system to achieve both high electro-optic coefficient and reduced velocity mismatch by optimizing the dielectric constant distribution across different layers.
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 the modulation efficiency and extends the operating band of the optical modulator, allowing for higher communication speeds with reduced power consumption.
Implementation Method 1
an electro-optic layer 33 including an electro-optic material... A first modulation unit 13A has a first ground electrode 22B, a signal electrode 22A, and a first modulation waveguide 21A... An electric field is generated from the signal electrode 212A to the first ground electrode 212B in the first modulation unit 203A according to a high frequency electric signal... and a change is caused in the optical refractive index of the first modulation waveguide 211A according to the electric field
Data Source
AI summary
An optical modulator includes an electro-optic layer including an electro-optic material, and a material layer arranged below the electro-optic layer and having a dielectric constant lower than a dielectric constant of the electro-optic layer. The optical modulator includes a core layer arranged below the material layer and having a refractive index higher than refractive indices of the electro-optic layer and the material layer, and an electrode that applies an electric signal to the electro-optic layer. The refractive index of the material layer is 0.85 times the refractive index of the electro-optic layer or higher.