Grating Slit Waveguide Sensor for High Sensitivity and Quality Factor
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Solution Overview
Problem
Current optical refractive index sensors face challenges in achieving high sensing sensitivity and quality factor simultaneously, which limits their figure of merit, as they either have low sensing sensitivity due to a small contact area between the light field and measured substances or a low quality factor due to strong local light effects.
Innovation Solution
A sensor based on a grating slit waveguide composite structure is developed, featuring a substrate with a recessed groove, a dielectric layer, and a metal layer forming a slit optical waveguide with a grating that enhances wave vector matching, allowing for high localization of the light field and resonant coupling, thereby improving both sensitivity and quality factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a microdisk-structured resonator is used to achieve high quality factor, then the quality factor increases to 10^8, but the sensing sensitivity becomes very low due to small contact area between light field and measured substances
Solution Approach 1:
The patent segments the light field interaction into two distinct functional regions: a microdisk resonator region for achieving high quality factor through resonant coupling, and a grating-coupled waveguide region for enhancing sensing sensitivity through extended evanescent field interaction with the analyte. This segmentation allows each region to optimize its specific function without compromising the other.
Solution Approach 2:
The patent merges two previously separate optical structures (microdisk resonator and grating-coupled waveguide) into a single integrated sensor system. The microdisk provides high-Q resonance while the waveguide region with grating coupling provides enhanced sensitivity through increased light-analyte interaction area, achieving both high quality factor and high sensing sensitivity simultaneously.
2Measurement precision
If metal nanoparticles are used to enhance local light field effect and interaction with measured object, then sensing sensitivity is greatly enhanced for non-absorbent single molecule detection, but the quality factor of resonance mode drops to merely over ten
Solution Approach 1:
The patent extracts the grating coupling mechanism from the metal nanoparticle structure and applies it to a dielectric waveguide system. This extraction allows the system to achieve enhanced light field interaction (sensitivity) through the grating's evanescent field without incorporating metal nanoparticles that would cause excessive loss and degrade the quality factor.
Solution Approach 2:
The patent introduces a grating structure as an intermediary element that mediates between the incident light and the waveguide mode. The grating provides the necessary momentum matching to couple light into the waveguide, creating an enhanced evanescent field for sensing while maintaining low loss and high quality factor through the use of dielectric materials rather than metal nanoparticles.
3Measurement precision
If a meta-material absorber with integrated microfluidic channel is used to implement full spatial coincidence of light field and measured object, then ultra-high sensitivity of 3.5 THz/RIU is achieved, but the quality factor remains only about 10
Solution Approach 1:
The patent copies the successful concept of spatial coincidence between light field and measured object from the meta-material absorber, but implements it using a different physical structure (grating-coupled waveguide with microfluidic channel) that avoids the inherent quality factor limitations of metamaterial absorbers. This copying allows achievement of high sensitivity through full spatial overlap while maintaining high quality factor through low-loss dielectric waveguide construction.
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 sensor achieves high sensing sensitivity and quality factor, resulting in an extremely high figure of merit, with a quality factor greater than 1000 and a figure of merit greater than 140, enabling effective detection of refractive index changes.
Implementation Method 1
a grating formed on the dielectric layer, or on the bottom surface of the first groove, or formed by the metal layer, wherein the grating is used to implement wave vector matching of an incident light with a mode of the slit optical waveguide
Implementation Method 2
the dielectric layer, the metal layer and an interval between the dielectric layer and the metal layer form a slit optical waveguide; and a grating formed on the dielectric layer
Implementation Method 3
the dielectric layer, the metal layer and an interval between the dielectric layer and the metal layer form a slit optical waveguide
Data Source
AI summary
A sensor including: a substrate including a first surface and a second surface opposing to each other, the first surface being recessed to form a first groove, and the substrate further including at least two through holes penetrating through the second surface and a bottom surface of the first groove; a dielectric layer disposed to cover the first surface, and opposing to the first groove; a metal layer disposed on the bottom surface of the first groove and avoiding openings of the through holes on the bottom surface of the first groove, wherein the dielectric layer, the metal layer and an interval between the dielectric layer and the metal layer form a slit optical waveguide; and a grating formed on the dielectric layer, wherein the grating is used to implement wave vector matching of an incident light with a mode of the slit optical waveguide.