Waveguide Lateral Strips for Spurious Mode Filtering
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Solution Overview
Problem
In integrated photonic circuits, inhomogeneities in waveguides can cause spurious optical modes, leading to destructive interferences and disturbances in signal transmission, as existing spurious mode filtering devices often impact the guided mode transmission negatively.
Innovation Solution
A waveguide design featuring lateral strips with varying thickness and material absorption along an intermediate portion, which progressively decreases in width and includes an absorbing material to filter out spurious modes without significantly affecting the guided mode, using a silicon-on-insulator structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spurious mode filtering devices are introduced to eliminate spurious modes, then the harmful interference from spurious modes is reduced, but the transmission of the guided mode is negatively impacted
Solution Approach 1:
The waveguide structure implements local quality by creating an intermediate portion with different geometric characteristics (reduced height or width) compared to the first and second portions. This localized structural variation enables the intermediate portion to selectively interact with spurious modes while allowing the guided mode to pass through with minimal disturbance, thus resolving the contradiction between filtering spurious modes and maintaining guided mode transmission.
Solution Approach 2:
The waveguide is segmented into distinct portions (first portion, intermediate portion, and second portion) with different geometric properties. This segmentation allows each portion to perform its specific function: the first and second portions guide the fundamental mode, while the intermediate portion with its reduced dimensions selectively filters spurious modes, achieving both objectives simultaneously.
2Object-generated harmful factors
If the waveguide dimensions are reduced to filter spurious modes, then spurious mode propagation is suppressed, but the guided mode transmission efficiency decreases
Solution Approach 1:
The waveguide structure employs dynamic geometric variation along its length, with the intermediate portion having different dimensions (reduced height or width) compared to the input and output portions. This dynamic structural change creates a gradual transition that enables selective mode filtering while maintaining guided mode transmission, preventing abrupt discontinuities that would cause excessive energy loss.
Solution Approach 2:
The waveguide utilizes parameter changes by varying the geometric parameters (height or width) along its length. The intermediate portion features modified dimensions that create a local effective index change, which selectively affects spurious modes while preserving guided mode propagation. This parameter variation approach enables effective filtering with minimal transmission loss.
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
Effectively filters spurious modes, reducing their power by over 95% while maintaining minimal impact on the guided mode transmission, ensuring reliable signal propagation without coupling disturbances.
Implementation Method 1
each second band is, along the intermediate portion, at least partially made of a material selected to absorb the wavelengths of a signal intended to be propagated through the waveguide
Data Source
AI summary
In one embodiment, a waveguide includes an upstream portion, a downstream portion, and an intermediate portion between the upstream portion and the downstream portion. A first band is disposed on an insulating layer, the first band oriented along a first direction. A first lateral strip and a second lateral strip are disposed on either side of the first band, the first lateral strip and the second lateral strip being thinner or interrupted along the intermediate portion.