Raman Spectrometer Fluorescence Rejection via Sequentially Shifted Excitation
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Solution Overview
Problem
Raman spectroscopy is hindered by intense fluorescence backgrounds, leading to reduced signal quality and increased acquisition times, and existing methods for fluorescence removal are either complex, expensive, or limited in applicability.
Innovation Solution
A handheld Raman spectrometer using a temperature-controlled diode laser with Bragg grating optical feedback, which acquires sequentially shifted excitation Raman spectra and processes them to eliminate fluorescence backgrounds while maintaining true spectral data, reducing noise and processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If long wavelength lasers (1064 nm) are used for FT-Raman spectroscopy, then fluorescence backgrounds are reduced, but Raman signal intensity decreases and acquisition time increases
Solution Approach 1:
The patent uses periodic modulation of the laser excitation source between two wavelengths, acquiring spectra at each wavelength in alternating fashion. This periodic switching enables the system to collect Raman signals at both wavelengths over time, then process them to eliminate fluorescence while maintaining reasonable acquisition speed
Solution Approach 2:
The patent changes the excitation wavelength parameter by modulating the laser between two different wavelengths (e.g., 785 nm and 830 nm). By acquiring spectra at multiple wavelengths and processing them together, the system achieves fluorescence rejection without the severe signal loss associated with single long-wavelength excitation
2Measurement precision
If multiple excitation wavelengths are used to remove fluorescence, then signal quality improves, but device complexity increases
Solution Approach 1:
The patent introduces a computer as an intermediary that performs the complex mathematical processing of spectra acquired at multiple wavelengths. The computer calculates weighted combinations of spectra to eliminate fluorescence, transferring the complexity from optical hardware to software processing
Solution Approach 2:
The patent replaces complex mechanical fluorescence rejection systems with a computational approach. Instead of using additional optical components or mechanical modulation devices, the system uses software algorithms to process spectra from a single modulated laser source
3Power
If higher laser power is used to compensate for reduced Raman signal, then signal intensity improves, but sample damage risk increases
Solution Approach 1:
By periodically switching between two excitation wavelengths, the system accumulates Raman signals from both wavelengths over the acquisition period. This allows the use of moderate laser powers at each wavelength while achieving sufficient total signal intensity through the combined spectral data
Solution Approach 2:
The patent creates a composite spectrum by mathematically combining spectra acquired at two different wavelengths with appropriate weighting. This composite approach achieves high signal intensity and fluorescence rejection simultaneously, avoiding the need for high laser power that would damage samples
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 enables rapid, high-quality Raman spectrum extraction with superior signal-to-noise performance, independent of excitation shifts, and allows for universal applicability with a single processing algorithm across multiple articles, effectively reducing random and thermal noise.
Implementation Method 1
a temperature-controlled diode laser with Bragg grating optical feedback
Implementation Method 2
Raman spectroscopy is hindered by intense fluorescence backgrounds
Implementation Method 3
acquires a plurality of sequentially shifted excitation Raman spectra
Implementation Method 4
intense fluorescence backgrounds resulting from impurities or from the population of a sample's excited state(s)
Data Source
AI summary
One embodiment of a Raman spectrometer having a temperature controlled diode laser with Bragg grating optical feedback 100 which provides a means for the acquisition of Raman spectra using sequentially shifted excitations and provides a means for spectral processing to obtain a Raman spectrum which is free from background interference such as fluorescence.