Curved Waveguide-End Optical Absorber for Low-Noise PICs
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Solution Overview
Problem
Existing photonic integrated circuits (PICs) suffer from stray optical signals that create background noise due to spiral optical absorbers having a large footprint and scattering optical signals into neighboring structures.
Innovation Solution
A photonic integrated circuit (PIC) with a waveguide having a terminal end surrounded by a multi-layered optical absorber with a curved shape, incorporating a light absorbing layer made of germanium or vanadate, which effectively captures stray optical signals while maintaining low back reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spiral optical absorbers are used to capture stray optical signals, then optical noise is reduced, but the footprint area increases and optical signals are scattered into neighboring structures
Solution Approach 1:
The optical absorber is designed with a curved shape instead of a straight linear structure. This curvature allows the absorber to follow the waveguide path more closely and capture stray optical signals more effectively without requiring additional space, thereby reducing the footprint area while maintaining optical noise reduction performance.
Solution Approach 2:
The optical absorber is positioned adjacent to the waveguide in a nested arrangement, where the absorber closely follows the waveguide contour. This nested configuration allows the absorber to be integrated into the existing waveguide structure without requiring separate dedicated space, thus reducing the overall footprint area while effectively capturing stray signals.
2Object-affected harmful factors
If spiral optical absorbers are used to capture stray optical signals, then optical noise is reduced, but optical signals are scattered into neighboring structures
Solution Approach 1:
The curved shape of the optical absorber allows it to follow the natural propagation path of optical signals along the waveguide. This geometry enables the absorber to capture stray signals that follow the curved waveguide path without causing them to scatter into neighboring structures, as the absorber is positioned to contain the signal absorption within the waveguide boundary.
Solution Approach 2:
The optical absorber is strategically positioned adjacent to specific portions of the waveguide where stray signal generation is most problematic. By concentrating the absorption function at these critical locations rather than using a comprehensive spiral structure, the absorber effectively reduces optical noise without causing widespread signal scattering into neighboring structures.
3Object-affected harmful factors
If multi-layered optical absorber with curved shape is used, then light absorption efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The optical absorber utilizes changes in material parameters (refractive index, absorption coefficient) through multiple layers with different compositions. This allows the structure to achieve superior light absorption efficiency by exploiting parameter variations across layers, while the curved geometry is achieved through standard semiconductor fabrication techniques that modify physical parameters rather than adding complex assembly steps.
Solution Approach 2:
The multi-layered optical absorber employs composite material structures with different layers having distinct optical properties. This composite approach enhances light absorption efficiency by addressing different wavelengths and propagation modes, while the layers can be deposited using existing semiconductor manufacturing processes, thereby managing manufacturing complexity through material selection rather than structural complexity.
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 optical absorber reduces optical noise and improves functional component performance by attenuating stray signals without increasing the circuit's footprint or requiring additional process steps, enhancing compatibility with current semiconductor processes.
Implementation Method 1
an optical absorber including a light absorbing layer over a silicon layer, the light absorbing layer including one of germanium and a vanadate
Data Source
AI summary
A photonic integrated circuit (PIC) includes a waveguide in or over a semiconductor substrate. The waveguide has a terminal end. The PIC also includes an optical absorber having a curved shape adjacent to opposing sides and an endwall of the terminal end of the waveguide, i.e., it surrounds the terminal end of the waveguide. The optical absorber is multi-layered and includes a light absorbing layer. The light absorbing layer may include germanium or a vanadate. The optical absorber terminates or attenuates any stray optical signals from the waveguide while maintaining low back reflection.