Hybrid Optical Element Tapers for Coupling and Low Capacitance
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Solution Overview
Problem
Hybrid optical elements applied to electro-absorption modulators face a trade-off between requiring long tapers for sufficient coupling and reducing parasitic capacitance, leading to increased device size and degradation in high-frequency characteristics.
Innovation Solution
A hybrid optical element structure with a p-InP layer, light absorbing layer, dielectric thin film, optical waveguide, and BOX layer, featuring a second taper with the light absorbing layer exposed and a third taper between the second taper and modulation part, designed to ensure sufficient coupling while minimizing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long tapers are used to ensure sufficient coupling between waveguides, then coupling efficiency is improved, but parasitic capacitance increases and device size becomes large
Solution Approach 1:
The invention changes the physical parameters of the taper structure by introducing a suspended configuration with air gap, transforming the conventional solid-structure taper into a suspended taper that achieves better coupling efficiency with shorter length, thereby reducing parasitic capacitance while maintaining coupling performance
Solution Approach 2:
The invention introduces a vertical dimension by suspending the taper structure above the substrate using an air gap, creating a three-dimensional configuration that improves coupling efficiency without increasing the horizontal footprint, thus reducing device size and parasitic capacitance
2Reliability
If long tapers are used to ensure sufficient coupling, then coupling efficiency is improved, but device area increases
Solution Approach 1:
The suspended taper structure utilizes the vertical air gap dimension to achieve enhanced coupling efficiency, allowing the device to maintain compact horizontal dimensions while improving optical coupling through the three-dimensional suspended configuration
Solution Approach 2:
By changing the structural parameters to include suspension and air gap, the invention achieves superior coupling efficiency in a shorter taper length, thereby reducing the overall device area while maintaining or improving coupling performance
3Object-affected harmful factors
If taper length is reduced to decrease parasitic capacitance, then high-frequency characteristics are improved, but coupling efficiency deteriorates
Solution Approach 1:
The suspended configuration with air gap introduces a vertical dimension that enhances optical field overlap and coupling efficiency, allowing shorter taper lengths to achieve sufficient coupling without the need for long horizontal extensions that would increase parasitic capacitance
Solution Approach 2:
The invention changes the physical state and configuration parameters of the taper by suspending it with an air gap, which fundamentally alters the coupling mechanism to achieve high coupling efficiency in shorter structures, thereby reducing parasitic capacitance while maintaining coupling performance
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
The structure achieves shortened tapers with sufficient coupling and reduced parasitic capacitance, improving high-frequency characteristics and reducing device size.
Implementation Method 1
an optical waveguide
Implementation Method 2
a light absorbing layer... optical absorption is limited to an area close to a p electrode
Data Source
AI summary
A hybrid optical element according to the presently disclosed technique includes: a p-InP; a light absorbing layer; an n-InP; a dielectric thin film; an optical waveguide; a BOX layer; and a core substrate in order from a surface, wherein the n-InP has a first taper, the light absorbing layer has a second taper, the light absorbing layer is exposed in the second taper, the p-InP includes a modulation part, a third taper is disposed between the second taper and the modulation part, the second taper is not provided in the p-InP, optical absorption is limited to an area close to a p electrode, and the third taper has a taper length which is five percent or less of the length of the modulation part.