Fluorescent Chemical Sensor Waveguide Integration
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Solution Overview
Problem
Existing fluorescence-based gas sensors face challenges in achieving high sensitivity due to the low conversion rate of exciting light to fluorescence, requiring a close proximity between the photodetector and sensing material while minimizing exposure to exciting light.
Innovation Solution
A CMOS-compatible chemical sensing device is developed, incorporating a semiconductor substrate with integrated circuit components, a photodetector, and a waveguide structure that couples electromagnetic radiation into and out of the sensing area, using gratings, scattering particles, or mirrors to direct radiation and an optical filter to block exciting light, allowing for a compact design and enhanced fluorescence detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the photodetector is placed close to the sensing material to maximize fluorescence detection, then the sensitivity is improved, but the photodetector is exposed to excessive exciting light which reduces measurement accuracy
Solution Approach 1:
The waveguide acts as an intermediary structure that selectively guides fluorescence photons from the sensing material to the photodetector while blocking the excitation light path. The waveguide's optical properties allow it to transmit specific wavelengths (fluorescence) while reflecting or absorbing others (excitation light), thus mediating between the light source, sensing material, and photodetector to resolve the contradiction between close proximity and light exposure.
Solution Approach 2:
The optical filter is positioned specifically between the waveguide and photodetector to provide localized wavelength selection. This local quality enhancement allows the system to maintain close geometric arrangement for high sensitivity while the filter locally removes harmful excitation light wavelengths before they reach the photodetector, ensuring measurement accuracy.
2Measurement precision
If the distance between photodetector and sensing material is reduced to increase signal strength, then the fluorescence detection capability is improved, but the device complexity increases due to light path management requirements
Solution Approach 1:
The waveguide integrates multiple functions into a single structure: it serves as both the optical transmission medium for fluorescence and the structural element that defines the compact light path. By merging the light guiding function with the spatial arrangement, the system achieves close photodetector-sensing material positioning without requiring complex external light path management components.
Solution Approach 2:
The waveguide structure performs multiple roles simultaneously: it guides fluorescence photons to the photodetector, blocks excitation light through its optical filtering properties, and provides structural support for the compact arrangement. This multi-functionality reduces the need for separate components, thereby reducing device complexity while maintaining high measurement precision.
3Device complexity
If a conventional sensor layout is used with light source between sensing material and photodetector, then the device structure is simpler, but the distance between photodetector and sensing material increases reducing sensitivity
Solution Approach 1:
Instead of placing the light source between the sensing material and photodetector as in conventional designs, the invention inverts the arrangement by positioning the photodetector adjacent to the sensing material with the light source positioned elsewhere. The waveguide then guides fluorescence laterally to the photodetector, inverting the traditional linear light path into a lateral guidance configuration that achieves both simplicity and high sensitivity.
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
This configuration significantly reduces the sensor size, increases detected fluorescence, and minimizes exciting light exposure to the photodetector, thereby enhancing sensitivity and efficiency.
Implementation Method 1
A waveguide is arranged in or above the dielectric. A portion of the waveguide is arranged at the source of electromagnetic radiation, so that the electromagnetic radiation emitted by the source of electromagnetic radiation is coupled into the waveguide.
Implementation Method 2
Gas detection by some types of opto-chemical gas sensors is based on a measurement of the fluorescence of a sensing material that changes its optical properties upon exposure to specific gases.
Implementation Method 3
an optical filter to block exciting light
Data Source
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AI summary
The chemical sensing device comprises a substrate (1) of semiconductor material, integrated circuit components (2) and a photodetector (3) formed in the substrate (1), a dielectric (4) on the substrate (1), a wiring (5) in the dielectric, and a source of electromagnetic radiation (6), a waveguide (9) and a fluorescent sensor layer (14) arranged in or above the dielectric. A portion of the waveguide is arranged to allow the electromagnetic radiation emitted by the source of electromagnetic radiation to be coupled into the waveguide. A further portion of the waveguide is arranged between the photodetector and the fluorescent sensor layer.