Optical Waveguide Evanescent Wave Interaction
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Solution Overview
Problem
Existing optical waveguide sensors face challenges in stably detecting substances with high sensitivity across various modes of use due to limited interaction between evanescent waves and the substance, and excessive absorption by support materials.
Innovation Solution
An optical waveguide design featuring a core layer supported by a material with a smaller refractive index, where the connecting portion of the support is shifted from the center to the outer surface, expanding the interaction region with the substance while minimizing absorption, and a protective film with nitrogen to prevent surface degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the support material is placed directly under the core layer to provide mechanical strength, then the mechanical strength is improved, but the absorption of evanescent waves by the support material increases and the interaction area with the substance decreases
Solution Approach 1:
The support structure is segmented into discrete support portions rather than a continuous layer, creating gaps between support regions. This segmentation allows the evanescent waves to extend into the substance through the gaps without being absorbed by continuous support material, while still providing mechanical strength at specific locations.
Solution Approach 2:
The support material is extracted from directly under the core layer and repositioned to peripheral portions. This removes the harmful absorption effect from the high-evanescent-field region while retaining the necessary mechanical support function at locations where evanescent wave absorption is less critical.
2Area of stationary object
If the support material is positioned at the peripheral portions rather than directly under the core layer, then the interaction area between evanescent waves and substance is improved, but the mechanical strength may be compromised
Solution Approach 1:
The support structure exhibits local quality by providing mechanical support at peripheral portions where evanescent wave absorption is minimized, while allowing the central region under the core layer to remain free for maximum evanescent wave-substance interaction. Each region is optimized for its specific function.
Solution Approach 2:
The support function is transitioned from a vertical dimension (directly under the core layer) to a horizontal dimension (peripheral portions). This dimensional change allows the support material to provide mechanical stability while being positioned outside the primary evanescent wave interaction zone.
3Reliability
If the core layer is fully supported by the substrate to ensure stability, then the mechanical stability is improved, but the sensitivity of substance detection decreases due to reduced evanescent wave-substance interaction
Solution Approach 1:
The support structure is segmented into discrete portions positioned at specific locations rather than providing continuous support. This allows the core layer to be mechanically stabilized at support points while maintaining open regions for maximum evanescent wave-substance interaction, thereby preserving detection sensitivity.
Solution Approach 2:
The support configuration is made asymmetric by positioning support portions at peripheral locations rather than centrally under the core layer. This asymmetric arrangement optimizes the balance between mechanical stability (provided by peripheral supports) and detection sensitivity (maintained by central interaction regions).
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
Enhances the sensitivity and stability of substance detection by increasing the interaction area between evanescent waves and the substance, while reducing absorption and maintaining mechanical strength and preventing surface oxidation.
Implementation Method 1
light propagating through the structure progresses while repeatedly undergoing total internal reflection at the boundary between the structure and the outside of the structure
Implementation Method 2
the light L not only propagates inside the structure 51 but also extends into the substance 53 that has a small refractive index. This extension is referred to as an evanescent wave
Implementation Method 3
the evanescent wave may be absorbed by the substance adjacent to the structure 51 while the light L propagates through the structure 51
Data Source
AI summary
An optical waveguide includes a core layer which extends along a longitudinal direction and through which light can propagate; and a protective film that is formed on at least a portion of a surface of the core layer and has a smaller refractive index than the core layer. At least a portion of the protective film is provided in a manner allowing contact with a gas or a liquid. In a cross-section of at least a portion perpendicular to a longitudinal direction of the core layer, the protective film is formed around the entire surface of the core layer.