Integrated Plasmo-Photonic Biosensor for High Sensitivity
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Solution Overview
Problem
Current biosensing technologies face challenges in achieving high sensitivity and miniaturization while maintaining low manufacturing costs, due to complex and expensive fabrication methods, large system footprints, and limited sensitivity in planar monolithic chips, which hampers their adoption in point-of-care and portable applications.
Innovation Solution
The integration of nanometer-scale plasmonic waveguides with optimally biased Mach-Zehnder interferometers using CMOS-compatible materials and fabrication processes, combined with thermo-optic phase shifters, to achieve ultra-high sensitivity and compactness, enabling mass manufacturing of ultra-sensitive biosensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical prism is used to couple light into surface plasmon mode, then sensitivity to refractive index change is improved, but system size becomes large and miniaturization is hindered
Solution Approach 1:
The patent extracts the coupling function from a bulky optical prism and integrates it directly into the planar waveguide structure through evanescent field coupling. The waveguide itself serves as the coupling interface, eliminating the need for separate prism components and enabling miniaturization while maintaining plasmonic coupling efficiency.
Solution Approach 2:
The patent transitions from three-dimensional prism-based coupling to two-dimensional planar waveguide coupling. By utilizing the evanescent field extending from the waveguide surface in the vertical dimension, the system achieves effective coupling without requiring large lateral dimensions, thus enabling miniaturization.
2Measurement precision
If plasmonic waveguides are integrated in Mach-Zehnder interferometers to enhance sensitivity, then optical sensitivity is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent segments the Mach-Zehnder interferometer into distinct functional modules: a plasmonic sensing waveguide section for analyte detection, photonic waveguide sections for light propagation, and integrated couplers for mode conversion. This modular segmentation simplifies manufacturing by allowing each section to be optimized and fabricated independently using CMOS-compatible processes.
Solution Approach 2:
The patent designs the waveguide structure to serve multiple functions: the plasmonic waveguide acts as both the sensing element and the coupling interface, while the photonic waveguides serve as both light guides and structural support. This multi-functionality reduces the number of separate components needed, thereby simplifying the overall device complexity.
3Productivity
If micrometer scale dimensions are used in MZI sensor, then integration is enabled, but sensitivity and resolution are limited due to absence of biasing components
Solution Approach 1:
The patent nests the plasmonic sensing waveguide within the photonic waveguide structure of the Mach-Zehnder interferometer. The plasmonic section is integrated into one arm of the MZI, allowing the sensing function to be embedded within the interferometric structure without requiring additional external components. This nested integration maintains compact dimensions while enabling sensitivity enhancement through the interferometric detection scheme.
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 approach results in unprecedented optical sensitivity of up to 162,000 nm/RIU, enabling accurate real-time detection of molecular-level substances and facilitating early disease diagnosis and environmental monitoring with reduced fabrication costs and system size.
Implementation Method 1
confines light propagation through coupling to Surface Plasmon Polaritons SPP at the metal-analyte interface
Implementation Method 2
tune the phase of the optical signal in the reference arm of each MZI by exploiting the thermo-optic effect of the Si3N4 waveguide
Implementation Method 3
An additional MZI, e.g. a second optical interferometric Mach-Zehnder MZI2, is used along with optical phase shifters
Data Source
Figure 1~4
Figure 5~10
AI summary
The invention relates to a device comprising a first optical Mach-Zehnder interferometric sensor (MZI1) with a large FSR, wherein a plasmonic waveguide (107) thin-film or hybrid slot, is incorporated as transducer element planar integrated on Si3N4 photonic waveguides and a second optical interferometric Mach-Zehnder (MZI2), both comprising thermo-optic phase shifters (104, 106) for optimally biasing said MZI sensor (MZI1) and MZI as variable optical attenuator VOA. It further comprises an overall chip (112), being remarkable in that it comprises a set of Photonic waveguides (103) with a high index silicon nitride strip (303, 603), which is sandwiched between a low index oxide substrate (Si02) and a low index oxide superstrate (LTO); Optical coupling structures (102, 109) at both ends of the sensor acting as the optical l/Os; an Optical splitter (102) and an optical combiner (109) for optical splitting at the first junction (102) of said first sensor (MZI1) and optical combining at the second junction (109) of said first MZI (MZI1); a variable optical attenuator (VOA) with said additional second MZI (MZI2), which is nested into said MZI1 (sensor)), deploying an optical splitter and an optical combiner for optical splitting at the first junction of said additional second MZI (MZI2), and optical combining at the second junction of said second MZI (MZI2); a set of Thermo-optic phase shifters (104, 106) to tune the phase of the optical signal in the reference arm (104, 106) of each said MZI (MZI1, MZI2-VOA); wherein Thermo-optic phase shifters are formed by depositing two metallic stripes parallel to each other on top of a section of the photonic waveguide and along the direction of propagation of light; and a plasmonic waveguide (107) in the upper branch (103) of said first MZI (MZI1), that confines light propagation through coupling to Surface Plasmon Polaritons (SPP) at the metal-analyte interface, and method associated thereto.