Germanium Rib Optical Modulator for Low Power Silicon Photonics
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Solution Overview
Problem
Current silicon-based optical modulators face challenges with high energy consumption and large on-chip area due to long phase shifter lengths, while silicon micro-ring resonators are susceptible to fabrication errors and have limited modulation bandwidth.
Innovation Solution
A Germanium rib-based optical modulator is developed, where a semiconductor substrate with Germanium rib is used between two waveguides, and electrodes apply an electrical field to modulate the signal, leveraging the Frank-Keldysh effect for enhanced optical absorption and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a silicon-based modulator uses free carrier plasma dispersion effect with long phase shifter length, then modulation function is achieved, but energy consumption increases and on-chip area increases
Solution Approach 1:
The patent changes the material parameter from silicon to germanium and utilizes the Frank-Keldysh effect instead of free carrier plasma dispersion effect. This parameter change enables achieving the same modulation function with significantly shorter interaction length, thereby reducing both energy consumption and on-chip area.
Solution Approach 2:
The patent employs a hybrid structure combining silicon waveguides with a germanium rib. This composite material approach leverages the superior electro-optic properties of germanium while maintaining compatibility with silicon photonics platforms, enabling compact and low-power modulation.
2Area of stationary object
If a silicon micro-ring resonator modulator is used, then on-chip area is reduced, but fabrication error susceptibility increases and modulation bandwidth is reduced
Solution Approach 1:
The patent divides the modulation function into two independent parts: the silicon waveguide structure for optical confinement and the germanium rib for electro-optic modulation. This segmentation allows each component to be optimized independently, reducing fabrication error susceptibility while maintaining compact size.
Solution Approach 2:
The germanium rib provides localized electro-optic modulation only where needed, rather than requiring the entire micro-ring structure to be sensitive to electrical fields. This local quality approach reduces fabrication sensitivity and maintains higher modulation bandwidth.
3Reliability
If hybrid integration of III-V semiconductor or lithium niobate modulators onto silicon platform is used, then modulation performance is achieved, but manufacturing cost increases and volume manufacturability is reduced
Solution Approach 1:
The patent uses germanium, which is chemically and structurally similar to silicon, enabling homogeneous integration within the silicon photonics ecosystem. This homogeneity allows the use of existing silicon CMOS fabrication processes, significantly reducing manufacturing cost and enabling volume production while maintaining high modulation 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 solution achieves lower energy consumption, smaller on-chip footprint, and potentially higher modulation speed, with improved compatibility with CMOS processing, enabling efficient encoding of optical signals in silicon photonics circuits.
Implementation Method 1
leveraging the Frank-Keldysh effect for enhanced optical absorption and reduced power consumption
Implementation Method 2
the first electrode and the second electrode are configured to apply an electrical field to the Germanium rib in order to modulate the input signal propagating through the Germanium rib
Data Source
AI summary
An optical modulator and a method for manufacturing an optical modulator are provided. The optical modulator includes a first waveguide, a second waveguide, a modulating portion connected between the first waveguide and the second waveguide, the modulating portion being configured to receive an input signal from the first waveguide, to modulate the input signal and to supply a corresponding modulated input signal as an output signal to the second waveguide, wherein the modulating portion includes a semiconductor substrate, one end thereof being coupled to the first waveguide, and a corresponding opposite end thereof being coupled to the second waveguide, a Germanium rib provided on the substrate such that the input signal propagates through the Germanium rib along a longitudinal axis thereof, and a first electrode and a second electrode respectively provided on the substrate, wherein the Germanium rib is provided between the first electrode and the second electrode, and wherein the first electrode and the second electrode are configured to apply an electrical field to the Germanium rib in order to modulate the input signal propagating through the Germanium rib.