Waveguide Sensor Attenuation Region Signal Noise Ratio
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Solution Overview
Problem
Fluorescence-based chemical sensors face challenges in achieving high signal-to-noise ratios due to poor coupling of non-Gaussian light beams with external components and crosstalk between sensor regions, limiting their sensitivity in detecting target chemicals.
Innovation Solution
Incorporating an in-line attenuation region with a wavelength-selective absorbing dye in the surface waveguide to selectively attenuate the excitation light, improving the signal-to-noise ratio by reducing noise from stimulative light while minimizing impact on the fluorescence signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a slab waveguide is used to increase the sensing region size and light propagation through the sensing region, then the interaction between chemically sensitive material and evanescent field is improved, but the light emission becomes non-Gaussian and coupling with external optical elements deteriorates
Solution Approach 1:
The waveguide is divided into distinct functional sections: a slab waveguide sensing region for chemical interaction and a single-mode waveguide section for coupling. This segmentation allows each section to be optimized for its specific function without compromising the other.
Solution Approach 2:
Different sections of the waveguide have different modal properties - the sensing region supports multi-mode propagation for enhanced interaction, while the coupling region is designed for single-mode operation. This local differentiation of waveguide properties resolves the contradiction between sensing performance and coupling efficiency.
2Measurement precision
If spectral filters are used to block the excitation signal at the photodetector, then the fluorescence signal detection is improved, but the filter formation becomes extremely difficult and expensive due to the slight wavelength difference
Solution Approach 1:
A wavelength-selective absorbing dye is introduced as an intermediary element within the waveguide. This dye selectively absorbs the excitation wavelength while transmitting the fluorescence wavelength, serving as a compact intermediary filter that eliminates the need for complex external spectral filters.
Solution Approach 2:
The absorbing dye's wavelength-selective properties are utilized to change the spectral composition of the light propagating through the waveguide. By selecting a dye with specific absorption characteristics, the system achieves wavelength discrimination without requiring complex filter structures.
3Adaptability or versatility
If arrays of fluorescence-based chemical sensor regions are used to detect multiple chemicals, then the detection capability is improved, but crosstalk between regions makes it difficult to differentiate fluorescence signals
Solution Approach 1:
Each sensor region in the array is surrounded by its own attenuation region containing wavelength-selective absorbing dye. This segmentation isolates the optical paths between adjacent regions, preventing crosstalk while maintaining the ability to detect multiple chemicals simultaneously.
Solution Approach 2:
Each sensor region is equipped with locally-specific wavelength-selective absorbing dye that is tuned to attenuate the excitation wavelength for that particular region. This local optimization ensures that fluorescence signals from adjacent regions do not interfere with each other.
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 of chemical sensors by improving the signal-to-noise ratio, allowing for more accurate detection of target chemicals with reduced noise interference.
Implementation Method 1
the first attenuation region comprises a second waveguide portion that receives light from the first sensing region, and wherein the first attenuation region attenuates light in the second waveguide portion such that light characterized by the first excitation wavelength is attenuated more than the first fluorescence signal
Implementation Method 2
the first material provides a first fluorescence signal that is characterized by a first fluorescence wavelength when exposed to (1) a first target chemical and (2) light that is characterized by a first excitation wavelength
Data Source
Figure 1~2
Figure 3~4A
Figure 4B~4D
AI summary
A sensor (100) for sensing a target chemical with high signal-to-noise ratio is disclosed. In some embodiments, the sensor (100) comprises a sensing region (108) that is optically coupled with an attenuation region (116). The sensing region receives optical stimulation that comprises light characterized by an excitation wavelength. In response to exposure to the target chemical, the sensing region (108) fluoresces at a fluorescence wavelength. The attenuation region (116) receives light from the fluorescing sensing region that includes light characterized by the fluorescence wavelength (i,e., signal) and light characterized by the excitation wavelength (i.e., noise). The attenuation region conveys the light to a detector (120) that provides an electrical output signal (122) based on the target chemical. While conveying the light, however, the attenuation region (116) improves the signal-to-noise ratio by attenuating light characterized by the excitation wavelength more than light characterized by the fluorescence region.