Polymer-Coated Silicon Waveguide for Miniaturized Acoustic Sensing
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Solution Overview
Problem
Piezoelectric transducers are limited by size-dependent sensitivity, electromagnetic interference, and resolution issues, making them unsuitable for miniaturized and EMI-immune applications like intravascular photoacoustic imaging and magnetoacoustics.
Innovation Solution
A fiber-coupled acoustic sensor with a high refractive index silicon waveguide core and a transparent polymer over-cladding, such as Benzocyclobutene (BCB), enhancing sensitivity and immunity to electromagnetic interference while allowing miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric transducers are used for ultrasound detection, then sensitivity is achieved, but the device size must be large which limits resolution and miniaturization
Solution Approach 1:
The patent replaces the mechanical piezoelectric transducer system with an optical waveguide-based interferometric detection system. The waveguide core made of high-index material (silicon) guides optical signals that are modulated by acoustic waves through the photoelastic effect, eliminating the need for large mechanical piezoelectric elements while achieving comparable or superior sensitivity.
Solution Approach 2:
The patent changes the refractive index parameter of the waveguide core material to a high value (silicon with n>2.0), which enhances the confinement of optical modes and increases the interaction length between light and acoustic waves. This parameter change enables miniaturization while maintaining detection sensitivity.
2Measurement precision
If piezoelectric transducers are used, then ultrasound detection is enabled, but electromagnetic interference vulnerability occurs
Solution Approach 1:
The patent substitutes the electromechanical piezoelectric transducer with an all-optical interferometric detection system. The waveguide detects acoustic waves through optical phase modulation caused by the photoelastic effect, making the system inherently immune to electromagnetic interference while maintaining ultrasound detection capability.
3Object-affected harmful factors
If optical interferometry is used for ultrasound detection, then electromagnetic interference immunity is achieved, but sensitivity reaches only above sub-Pascal levels which is insufficient for high-resolution imaging
Solution Approach 1:
The patent changes the refractive index parameter of the waveguide core to a high value (silicon with n>2.0), which enhances the optical mode confinement and increases the effective interaction length between light and acoustic waves. This parameter optimization enables the interferometric system to achieve sub-Pascal sensitivity required for high-resolution intravascular imaging.
Solution Approach 2:
The patent employs a composite waveguide structure with a high-index silicon core and a polymer cladding layer. This composite material approach optimizes both the optical confinement (through high-index contrast) and the photoelastic response (through the polymer coating), achieving enhanced sensitivity while maintaining EMI immunity.
4Volume of moving object
If high-index waveguide core is used, then miniaturization is enabled, but photoelastic response may be insufficient without proper cladding
Solution Approach 1:
The patent uses a composite structure combining a high-index silicon waveguide core with a polymer cladding layer. The high-index core enables miniaturization and strong optical confinement, while the polymer cladding provides enhanced photoelastic response to acoustic waves, creating a synergistic effect that achieves both miniaturization and high sensitivity.
Solution Approach 2:
The patent applies different material properties to different parts of the waveguide structure: the core uses high-index material for optical confinement and miniaturization, while the cladding uses polymer material with high photoelastic coefficient for enhanced acoustic sensitivity. This local optimization of material properties resolves the contradiction between size and 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
The sensor achieves high sensitivity and immunity to electromagnetic interference, enabling miniaturized and high-resolution ultrasound detection suitable for medical applications like intravascular imaging and magnetoacoustics.
Implementation Method 1
the over-cladding photo-elastic coefficient is greater than a magnitude of the waveguide core photo-elastic coefficient
Implementation Method 2
The waveguide core refractive index is greater than the over-cladding refractive index
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
Apparatus is provided including an acoustic sensor (50) having an optical waveguide (20). The optical waveguide (20) includes a waveguide core (202) having a waveguide core refractive index and a waveguide core photo-elastic coefficient, and an over-cladding layer (204) coupled to the waveguide core (202) and including an optically transparent polymer having an over-cladding refractive index and an over-cladding photo-elastic coefficient. The waveguide core refractive index is greater than the over-cladding refractive index, and the over-cladding photo-elastic coefficient is greater than the waveguide core photo-elastic coefficient. Other applications are also described.