Deep UV Semiconductor Lasers for Raman Spectroscopy
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Solution Overview
Problem
Current chemical analysis methods face challenges with the limited availability of suitable deep UV radiation sources for Raman spectroscopy, leading to low sensitivity and interference from fluorescence backgrounds, particularly in the visible spectrum, which hampers the detection of Raman signals and requires derivatization of analytes or the use of powerful lasers that can damage samples.
Innovation Solution
The development of electron-beam-pumped semiconductor radiation sources, such as AlGaN and diamond-based devices, that emit in the deep UV range below 300 nm, reducing system size, weight, and power consumption, while minimizing fluorescence interference and enhancing Raman signal strength through resonance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visible or near-IR lasers are used for Raman spectroscopy, then Raman signals can be detected, but fluorescence backgrounds interfere with detection and reduce sensitivity
Solution Approach 1:
The patent inverts the conventional approach by using deep UV radiation (193-280 nm) instead of visible or near-IR lasers for excitation. This wavelength inversion eliminates fluorescence interference because most materials do not exhibit fluorescence in the deep UV range, while simultaneously enhancing Raman scattering signals through resonance effects with electronic transitions.
Solution Approach 2:
The patent changes the excitation wavelength parameter from the conventional visible/near-IR range to the deep UV range (193-280 nm). This parameter change fundamentally alters the interaction between radiation and matter, suppressing fluorescence while enhancing Raman signals through resonance with electronic transitions, thereby resolving the contradiction between signal detection and fluorescence interference.
2Measurement precision
If powerful lasers are used to enhance Raman signals, then detection sensitivity improves, but sample damage occurs
Solution Approach 1:
The patent changes the excitation wavelength to deep UV (193-280 nm), which enables resonance enhancement of Raman signals. This resonance effect provides signal amplification without requiring the high power levels that cause sample damage with conventional visible or near-IR excitation, thus resolving the contradiction between detection sensitivity and sample integrity.
Solution Approach 2:
The patent converts the typically harmful high-power laser requirement into a benefit by using deep UV resonance excitation. The resonance effect naturally amplifies Raman signals, eliminating the need for high power that would otherwise damage samples, thereby transforming the potential harm into a beneficial signal enhancement mechanism.
3Measurement precision
If deep UV sources are used for Raman spectroscopy, then fluorescence interference is reduced and Raman signals are enhanced, but suitable radiation sources are limited
Solution Approach 1:
The patent employs a tunable deep UV source that can operate across the 193-280 nm wavelength range, enabling a single device to serve multiple analytical functions. This universal source can be tuned to match different electronic transitions of various analytes, providing both enhanced Raman signals and reduced fluorescence interference across diverse chemical compounds.
Solution Approach 2:
The patent uses a dynamically tunable deep UV source that can adjust its wavelength within the 193-280 nm range. This dynamic capability allows optimization of excitation wavelengths for different analytes and experimental conditions, overcoming the limitation of fixed-wavelength sources while maintaining the benefits of deep UV excitation.
4Measurement precision
If derivatization is performed to enable detection, then detectability of analytes improves, but analysis time and complexity increase
Solution Approach 1:
The patent extracts the need for derivatization by using deep UV resonance Raman spectroscopy. This technique directly detects the analyte in its native state by exploiting electronic transitions, eliminating the time-consuming derivatization step while maintaining or improving detectability through resonance enhancement of Raman signals.
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
These sources enable more sensitive and specific chemical analysis by increasing Raman scattering efficiency, reducing fluorescence interference, and allowing for smaller, more efficient analytical instruments capable of detecting a wider range of chemical compounds without sample damage.
Implementation Method 1
electron-beam-pumped semiconductor radiation sources, such as AlGaN and diamond-based devices, that emit in the deep UV range below 300 nm
Implementation Method 2
deep UV sources of radiation generated by electron-beam-pumped, wide bandgap, semiconductor devices
Implementation Method 3
Raman scattered radiation. Fluorescence or phosphorescence emissions are red shifted from the excitation frequency
Implementation Method 4
enhancing Raman signal strength through resonance effects
Implementation Method 5
reducing fluorescence interference. When the energy of the excitation radiation corresponds to strong absorption bands of the analyte, a resonance effect can amplify the Raman signal by many orders of magnitude
Data Source
AI summary
Spectroscopic chemical analysis methods and apparatus are disclosed which employ deep ultraviolet (e.g. in the 200 nm to 300 nm spectral range) electron beam pumped wide bandgap semiconductor lasers, incoherent wide bandgap semiconductor light emitting devices, and hollow cathode metal ion lasers to perform non-contact, non-invasive detection of unknown chemical analytes. These deep ultraviolet sources enable dramatic size, weight and power consumption reductions of chemical analysis instruments. In some embodiments, Raman spectroscopic detection methods and apparatus use ultra-narrow-band angle tuning filters, acousto-optic tuning filters, and temperature tuned filters to enable ultra-miniature analyzers for chemical identification. In some embodiments Raman analysis is conducted along with photoluminescence spectroscopy (i.e. fluorescence and/or phosphorescence spectroscopy) to provide high levels of sensitivity and specificity in the same instrument.