Photonic Integrated Circuit Light Absorbing Structures
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Solution Overview
Problem
Conventional WDM optical communication systems face challenges in minimizing optical feedback and noise due to scattered light, which becomes impractical as photonic integrated circuits (PICs) increase in density and size, especially with discrete components and separate substrates.
Innovation Solution
Integration of absorbing and scattering devices on PICs using semiconductor layers and metal absorption, along with geometric structures like spiral waveguides and multi-mode interference (MMI) devices to capture and disperse unwanted light, reducing interference with optical signals and lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If discrete components and separate substrates are used in conventional WDM optical communication systems, then component functionality is maintained, but device complexity and integration difficulty increase as PIC density and size increase
Solution Approach 1:
The patent merges multiple discrete optical components (lasers, modulators, detectors, amplifiers) onto a single photonic integrated circuit substrate. This consolidation eliminates the need for separate component mounting and interconnection, directly reducing integration difficulty while maintaining all necessary optical functions.
Solution Approach 2:
The PIC substrate is designed to perform multiple functions simultaneously - housing lasers for light generation, modulators for signal encoding, detectors for light detection, and amplifiers for signal boosting. This multi-functional integration reduces the number of separate components needed, thereby reducing device complexity.
2Object-affected harmful factors
If waveguides are tilted or angled to reduce scattering back into source waveguides, then optical feedback to lasers is reduced, but device complexity and layout difficulty increase
Solution Approach 1:
Instead of attempting to eliminate scattered light through complex waveguide tilting, the patent converts the harmful scattered light into a beneficial function by positioning photodetector elements to detect this scattered light. The previously harmful scattering effect is now utilized for monitoring and feedback control, reducing optical feedback without requiring complex waveguide geometries.
Solution Approach 2:
The patent introduces photodetector elements as intermediary components between the waveguides and the laser sources. These detectors capture scattered light and provide feedback signals that enable active control to suppress optical feedback, avoiding the need for complex passive waveguide geometries.
3Object-affected harmful factors
If additional waveguides are provided at dump ports to direct unwanted light away, then optical interference is reduced, but device complexity and space requirements increase
Solution Approach 1:
The patent converts the previously wasted unwanted light at dump ports into a useful signal by positioning photodetector elements to detect this light. This eliminates the need for additional waveguides to carry away unwanted light, as the detection function replaces the directional guidance function, thereby reducing device complexity and space requirements.
Solution Approach 2:
The photodetector elements enable the system to self-monitor and self-regulate optical interference by detecting scattered and unwanted light directly at the source locations. This active self-service approach replaces the passive structural solution of additional waveguides, reducing overall device complexity.
4Productivity
If higher density and size of PIC components are achieved, then functionality is enhanced, but conventional approaches to reducing scattered light become impractical
Solution Approach 1:
The patent replaces the mechanical/structural approach to scatter light reduction (waveguide tilting, additional waveguides at dump ports) with an optical detection and feedback approach using photodetector elements. This substitution enables effective scatter light management in high-density PIC layouts where conventional structural methods become impractical.
Solution Approach 2:
The patent changes the approach from passive structural modification to active optical parameter control by using photodetectors to detect scattered light and generate feedback signals. This enables dynamic adjustment of optical parameters to suppress feedback, making it feasible in high-density PIC configurations where static structural solutions are impractical.
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
Minimizes optical feedback to lasers, reduces phase, amplitude, and spectral noise, and maintains compact PIC layouts without power consumption or heating, as these passive devices do not require electrical bias.
Implementation Method 1
absorbing devices can include metallic absorption devices... light that is captured in the core may be absorbed by a metal layer
Implementation Method 2
scattering structures... a spiral waveguide structure that scatters initially guided light
Implementation Method 3
MMI devices... multi-mode interference (MMI) devices to capture and disperse unwanted light
Implementation Method 4
tapered waveguide structures... tapered waveguide structures that scatter light
Data Source
AI summary
A photonic integrated circuit is provided that may include a substrate; one or more optical sources, on the substrate, to output light associated with a corresponding one or more optical signals; one or more waveguides connected to the one or more optical sources; a multiplexer connected to the one or more waveguides; and one or more light absorptive structures, located on the substrate adjacent to one of the one or more optical sources, one of the one or more waveguides, and/or the multiplexer, to absorb a portion of the light associated with at least one of the corresponding one or more optical signals.