Hybrid III-V Laser Coupled to Silicon Waveguide
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Solution Overview
Problem
Integrated circuits face limitations in frequency and performance due to electrical interconnections, which can be addressed by replacing them with optical interconnections, but silicon's poor light-emitting properties require the integration of III-V semiconductors, leading to a compromise between laser threshold and power extraction efficiency in hybrid III-V/Si lasers.
Innovation Solution
A distributed feedback laser device is designed with a specific grating pitch and length to achieve resonant contradirectional coupling between the III-V stack and the SOI waveguide, allowing for efficient power extraction and maintaining low laser threshold, by optimizing the grating pitch and length to enable loop circulation of optical power from the III-V stack to the SOI waveguide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the laser mode is mainly guided in the III-V stack, then the modal gain is favored, but the power extraction efficiency towards the silicon waveguide deteriorates
Solution Approach 1:
The patent introduces an optical grating as an intermediary element that mediates the coupling between the III-V stack and the silicon waveguide. The grating acts as a distributed reflector that enables resonant contradirectional coupling, allowing optical power to loop from the III-V stack to the waveguide while maintaining both high modal gain and high power extraction efficiency.
Solution Approach 2:
The patent optimizes specific parameters including the grating pitch (chosen so that the optical power loops from the III-V stack to the waveguide), the grating length, and the coupling coefficient. By carefully selecting these parameters, the system achieves resonant contradirectional coupling that simultaneously maximizes modal gain in the III-V stack and power extraction efficiency into the silicon waveguide.
2Loss of energy
If the laser mode is mainly guided in the silicon layer, then the power extraction efficiency towards the silicon waveguide is favored, but the modal gain deteriorates
Solution Approach 1:
The optical grating serves as a mediator that enables bidirectional coupling between the silicon waveguide and the III-V stack. The grating's periodic structure creates resonant conditions that allow optical power to efficiently transfer from the III-V stack to the silicon waveguide while maintaining strong modal gain in the gain medium.
Solution Approach 2:
The patent carefully selects the grating pitch and length parameters to achieve optimal resonant contradirectional coupling. The grating pitch is specifically chosen so that the optical power loops from the III-V stack to the waveguide, and the grating length is optimized to achieve the desired coupling strength, thereby simultaneously maximizing both power extraction efficiency and modal gain.
3Reliability
If a hybrid III-V/Si laser structure is used, then both laser threshold and power collected in the silicon waveguide can be optimized, but the device complexity increases
Solution Approach 1:
The patent combines the III-V semiconductor stack (providing optical gain) with the silicon waveguide (providing low-loss transmission) into a hybrid integrated structure. This merging allows the system to benefit from both materials' advantages: the III-V stack provides low laser threshold through high modal gain, while the silicon waveguide provides efficient power collection and guidance.
Solution Approach 2:
The optical grating acts as an intermediary that enables efficient coupling between the III-V stack and the silicon waveguide. By introducing this periodic structure, the patent achieves resonant contradirectional coupling that facilitates bidirectional optical power transfer, thereby optimizing both laser threshold and power collection while maintaining a relatively compact integrated design.
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 allows for high power extraction efficiency while benefiting from the gain in the III-V stack, relaxing thickness constraints, and facilitating technological integration, with the potential for single-mode operation and reduced wavelength variation.
Implementation Method 1
a periodic structure which acts as a selective reflector in wavelength, distributed along the gain material
Implementation Method 2
The III-V stack 5 is a guiding structure having gain whose function is to generate photons
Implementation Method 3
The silicon layer 3 is a passive SOI waveguide whose function is to collect the photons generated in the III-V stack and to guide them
Data Source
Figure 1~3
Figure 4~6
AI summary
The method involves choosing spacing of an optical network (9) such that an optical power of a laser beam circulates in loop from a stack (5) of III-IV semiconductor materials to a silicon-on-insulator waveguide (3). The waveguide is formed by a part of a silicon-on-insulator structure, and is partially covered by the stack of semiconductor materials. The network is formed by periodical cavities hollowed in an upper surface of the waveguide, where the waveguide is made of silicon coated with silicon dioxide.