Raman Microscope Fluorescence Suppression via Stimulated Emission
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Solution Overview
Problem
Conventional Raman microscopes face challenges in achieving high wavenumber resolution and signal-to-noise ratio due to fluorescence interference, which is exacerbated by the higher intensity of fluorescence emission compared to Raman scattering, leading to difficulties in separating Raman and fluorescence spectra, especially in samples that emit strong fluorescence.
Innovation Solution
A Raman microscope utilizing continuous pump light and relaxation light to induce stimulated emission, with a dichroic mirror separating Raman scattered light, and a detector configured to detect spontaneous Stokes Raman scattered light, while the relaxation light has a wavelength different from the Raman scattered light, effectively suppressing fluorescence and enhancing signal-to-noise ratio through spectral separation and modulation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Raman spectroscopy is used to measure samples, then Raman scattered light can be detected, but fluorescence emission interferes with the measurement and reduces signal-to-noise ratio
Solution Approach 1:
The patent converts the harmful fluorescence emission into a beneficial signal by using stimulated emission. The relaxation light induces stimulated emission from fluorescent molecules, generating photons at the relaxation light wavelength that can be detected to represent the Raman spectrum, thereby transforming fluorescence from a harmful interference into a useful detection mechanism
Solution Approach 2:
The patent changes the detection parameter from measuring Raman scattered light directly to measuring stimulated emission photons generated by relaxation light. By detecting photons at the relaxation light wavelength rather than at Raman shifted wavelengths, the system avoids fluorescence interference while still obtaining Raman spectral information through the stimulated emission process
2Measurement precision
If pump light intensity is increased to improve Raman signal, then signal-to-noise ratio improves, but fluorescence emission intensity increases more and overwhelms the Raman signal
Solution Approach 1:
The patent converts the harmful fluorescence emission into a beneficial signal by using stimulated emission. The relaxation light induces stimulated emission from fluorescent molecules, generating photons at the relaxation light wavelength that can be detected to represent the Raman spectrum, thereby transforming fluorescence from a harmful interference into a useful detection mechanism
Solution Approach 2:
The relaxation light acts as an intermediary that mediates between the pump light and the detector. Instead of directly detecting Raman scattered light that is overwhelmed by fluorescence, the relaxation light induces stimulated emission that produces photons at a different wavelength, serving as an intermediate signal that carries Raman information without the fluorescence interference problem
3Loss of information
If Stokes Raman scattering is measured to observe Raman spectra, then Raman information can be obtained, but the spectra overlap with fluorescence spectra making separation difficult
Solution Approach 1:
The patent segments the detection process by separating the excitation function (pump light) from the detection function (relaxation light). By using a different wavelength for excitation and detection, the method divides the problematic overlapping spectral region into distinct wavelength domains, eliminating the overlap between Raman and fluorescence spectra
Solution Approach 2:
Instead of the conventional approach of exciting with one wavelength and detecting at a longer wavelength (Stokes shift), the patent inverts the detection approach by using a longer wavelength (relaxation light) to probe the sample and detecting at that same wavelength. This inversion of the excitation-detection wavelength relationship avoids the fluorescence overlap region
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 allows for high wavenumber resolution measurements with improved signal-to-noise ratio by suppressing fluorescence and narrowing the pump light line width, enabling effective Raman spectroscopy even in samples with strong fluorescence emission.
Implementation Method 1
a relaxation light source for emitting relaxation light to induce stimulated emission in a sample
Implementation Method 2
Raman scattered light from a sample is spectrally separated
Data Source
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AI summary
An object of the present invention is to provide a Raman microscope and a Raman spectrometric measuring method, both of which can make a measurement with high wavenumber resolution. The Raman microscope according to one embodiment of the present invention includes a pump light source 12 for emitting pump light as continuous light; a relaxation light source 11 for emitting relaxation light to induce stimulated emission in a sample; a dichroic mirror 14 for irradiating the relaxation light and the pump light to the sample 17; a spectrograph 32 for spectrally separating Raman scattered light generated in the sample 17; and a detector 33 for detecting the Raman scattered light spectrally separated in the spectrograph 32.