Hybrid Plasmonic Waveguide Coupling for Biosensor Sensitivity

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Solution Overview

Problem

Conventional surface plasmon polariton (SPP) biosensors require multiple components, are difficult to control, have low sensitivity, and are unstable, limiting their application for detecting refractive index changes in ultrathin layers.

Innovation Solution

A hybrid coupling structure combining short/long range surface plasmon polaritons with dielectric waveguides, including a dielectric substrate, waveguide layer, coupling matching layer, and surface plasmon waveguide, optimized for refractive index detection with adjustable refractive indices and thicknesses to enhance sensitivity and integration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional SPP biosensor structure is used, then the sensor can detect refractive index changes, but the device requires multiple components (prism, rotation table) resulting in large volume and complex structure

Engineering Contradiction:

Improverefractive index detection sensitivityVSAvoidnumber of components

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the prism coupling structure and the SPP sensor structure into a single integrated device. The dielectric waveguide serves both as the coupling element (replacing the prism) and as the sensor structure, eliminating the need for separate prism and rotation table components while maintaining the ability to detect refractive index changes through SPP resonance.

Inventive Principle:

Principle #5Merging (Combining)

2Measurement precision

If a conventional SPP biosensor structure is used, then the sensor can detect refractive index changes, but the control and stability are difficult to maintain

Engineering Contradiction:

Improverefractive index detection sensitivityVSAvoiddetection stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical rotation table with a fixed dielectric waveguide structure. The coupling angle is determined by the waveguide geometry and refractive indices rather than mechanical rotation, eliminating mechanical instability and improving detection reliability while maintaining sensitivity to refractive index changes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Length of moving object

If SRSPP mode is used for detection, then the coupling length and device size can be reduced, but the propagation loss increases significantly

Engineering Contradiction:

Improvecoupling lengthVSAvoidpropagation loss

Core Design Contradiction:

Length of moving objectVSLoss of energy

Solution Approach 1:

The patent introduces a dielectric waveguide as an intermediary between the light source and the SRSPP mode. The waveguide confines and guides the electromagnetic field, enabling efficient coupling to the SRSPP mode over a short distance while reducing energy loss through the metal film by confining the field primarily in the dielectric region.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Length of moving object

If the metal film thickness is reduced to enable SRSPP mode, then the coupling length decreases, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvecoupling lengthVSAvoidmetal film thickness control

Core Design Contradiction:

Length of moving objectVSManufacturing precision

Solution Approach 1:

The patent optimizes the metal film thickness parameter to a specific range (5-20 nm) that enables SRSPP mode formation while maintaining manufacturability. This parameter optimization, combined with the dielectric waveguide structure, achieves short coupling length without requiring extremely precise thickness control that would be necessary for thinner films.

Inventive Principle:

Principle #35Parameter changes

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 hybrid structure enables high-sensitivity, real-time detection of refractive index changes with reduced component complexity, improved stability, and low power consumption, addressing the limitations of conventional SPP sensors.

Implementation Method 1

A surface plasmon polariton (SPP) is an electromagnetic field propagating along the interface between a metal and a dielectric

Methodology Applied

Scientific EffectSurface plasmon polariton:

Implementation Method 2

When the distance between a metal waveguide and a dielectric waveguide is sufficiently small, a conventional dielectric waveguide mode develops coupling with an SPP mode under constant conditions

Methodology Applied

Scientific EffectEvanescent field coupling:

Data Source

PatentUS8358880B2Hybrid coupling structure of the short range plasmon polariton and conventional dielectric waveguide, a coupling structure of the long range plasmon polariton and conventional dielectric waveguide, and applications thereof

Publication Date: 2013.01.22 TSINGHUA UNIVERSITY

AI summary

The present invention provides a hybrid coupling structure of a short range surface plasmon polariton and a conventional dielectric waveguide, including a dielectric substrate layer, a dielectric waveguide layer positioned on the said dielectric substrate layer, a coupling matching layer positioned on the said dielectric waveguide layer and a short range surface plasmon waveguide portion, formed on the said coupling matching layer, for conducting the short range surface plasmon polariton. The present invention also provides a coupling structure of a long range surface plasmon polariton and a dielectric waveguide, including a dielectric substrate layer, a dielectric waveguide layer, a coupling matching layer and a long range surface plasmon waveguide portion upward from below respectively.