Evanescent-Wave Multimodal Optical Imaging for Surface-Specific Analysis
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Solution Overview
Problem
Current nonlinear optical imaging techniques often require separate platforms for different modalities, limiting the ability to access complementary chemical and structural information from a sample using total internal reflection (TIR) excitation.
Innovation Solution
A multimodal nonlinear optical imaging system that utilizes an oscillator, beam splitter, photonic crystal fiber, controllable beam block, objective optics, filter module, and camera to enable simultaneous operation of multiple imaging modes such as CARS, TPF, SHG, and SFG by leveraging total internal reflection excitation, allowing for selective activation and filtering of different spectral bands based on user input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate platforms are used for different nonlinear optical imaging modalities, then each modality can be optimized independently, but the system complexity increases and the ability to access complementary chemical and structural information from the same sample is limited
Solution Approach 1:
The patent combines multiple nonlinear optical imaging modalities (CARS, TPF, SHG, SFG) into a single integrated platform that uses a shared laser source, beam splitting system, and detection pathway. This merging allows simultaneous access to complementary chemical and structural information from the same sample while reducing overall system complexity compared to maintaining separate platforms for each modality.
Solution Approach 2:
The imaging platform is designed with universal components that can perform multiple functions: a single laser source generates pulses for all four modalities, a beam splitter distributes light to multiple modalities, and a single detection system can capture signals from any modality. This multi-functionality enables the system to access diverse sample information through one integrated instrument.
2Illumination intensity
If point scanning techniques are used to provide sufficiently high excitation field for nonlinear optical phenomena, then the required excitation intensity is achieved, but the imaging speed and productivity are reduced
Solution Approach 1:
The system uses periodic pulsed laser excitation with femtosecond-duration pulses at high repetition rates to deliver intense excitation fields intermittently. This periodic action allows the use of wider beam profiles (including evanescent waves) without continuous high power exposure, enabling both high peak intensities for nonlinear effects and faster imaging through parallel wide-field illumination rather than slow point scanning.
Solution Approach 2:
The patent transitions from one-dimensional point scanning to utilizing evanescent waves that provide two-dimensional wide-field illumination at the sample interface. This dimensional change allows simultaneous excitation of multiple points across the field of view, dramatically increasing imaging speed while maintaining sufficient excitation intensity through the concentrated evanescent field near the interface.
3Measurement precision
If total internal reflection excitation is used to generate evanescent waves for enhanced surface sensitivity, then the depth resolution and surface specificity are improved, but the system requires precise alignment and control
Solution Approach 1:
The system uses a dielectric substrate as an intermediary between the incident laser beam and the sample. The substrate enables total internal reflection and evanescent wave generation with relaxed alignment tolerances compared to direct air-sample interface TIRF. The substrate acts as a mediator that facilitates precise evanescent field confinement while providing a stable, easily controllable platform for achieving the desired surface specificity and depth resolution.
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
Enables the acquisition of complementary chemical and structural information from a sample using multiple nonlinear optical imaging modes on a single platform, improving the depth and detail of imaging by accessing various spectral bands and reducing the need for point scanning techniques.
Implementation Method 1
redirect the at least one received beam through a dielectric substrate towards an interface between a sample and a dielectric substrate to cause total internal reflection (TIR) of at least one redirected beam at the sample-substrate interface
Implementation Method 2
The responsive light may have a spectrum that comprises a first-beam-induced second-harmonic generation (p-SHG) spectral band
Implementation Method 3
a first-beam-induced two-photon fluorescence (p-TPF) spectral band
Implementation Method 4
The filter module may be configured to receive, from the objective optics, the backwards-propagating beam, and selectively filter the spectrum of the responsive light
Data Source
AI summary
A system for multimodal nonlinear optical imaging is provided. Each mode uses a high NA objective to cause total internal reflection excitation at a sample-substrate interface. The system has a femtosecond oscillator to generate pulses used for two beams. The objective receives at least one beam, redirects the received at least one beam through a dielectric substrate to cause the TIR and produces corresponding evanescent waves in a portion of the sample adjacent to the sample-substrate interface, and collects a backward-propagating beam of pulses of responsive light. The portion of the sample illuminated by the evanescent waves emits responsive light. Different modes or combinations of the distinct modalities may be selected to access complementary chemical and structural information for various chemical species near the sample-substrate interface. Each mode may have mode-specific control such as selective beam blocking, power ratios and filtering.