Spatial Heterodyne Raman Spectrometer for High Resolution
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Solution Overview
Problem
Current Raman spectroscopy technologies face challenges in achieving high spectral resolution and wide-area measurement capabilities in a small form factor, particularly for deep-UV applications, which are essential for measuring biomarkers and other samples like minerals, water, or CO2 ice, due to limitations in existing dispersive approaches and the need for large spectrographs with narrow slits.
Innovation Solution
The development of a miniature spatial heterodyne Raman spectrometer (SHRS) with a design that includes a first spatial heterodyne interferometer for filtering wavelengths and a second interferometer for Raman wavelengths, utilizing tilted diffraction gratings and field-widening prisms to achieve high spectral resolution and wide-area measurement capabilities without moving parts, compatible with pulsed laser excitation and gated detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dispersive (grating) approaches are used for UV Raman spectroscopy, then spectral resolution can be achieved, but the spectrometer size becomes large and requires narrow slits that reduce light throughput
Solution Approach 1:
The patent replaces the traditional mechanical dispersive spectrometer system with a spatial heterodyne interferometer that uses optical interference instead of mechanical dispersion. This substitution eliminates the need for large spectrographs and narrow slits, achieving high spectral resolution through interferometric fringes while maintaining a compact form factor suitable for portable and space applications.
Solution Approach 2:
The patent changes the fundamental operating parameter from wavelength dispersion to optical path difference interference. By using a spatial heterodyne interferometer with tilted diffraction gratings, the system measures spectral information through fringe patterns that encode wavenumber data, allowing high resolution without the size constraints of traditional dispersive systems.
2Area of stationary object
If traditional spectrometer designs are used, then spectral measurement capability is provided, but wide-area measurement capability and high light throughput cannot be achieved simultaneously
Solution Approach 1:
The spatial heterodyne interferometer provides multiple functions simultaneously: it achieves wide-area measurement capability through its large acceptance angle while maintaining high light throughput via the interferometric measurement approach. The system can perform both spatially resolved spectroscopy and high-throughput spectral measurement, making it versatile for various applications including imaging and remote sensing.
3Measurement precision
If high spectral resolution is achieved through traditional methods, then measurement precision improves, but device complexity and form factor increase
Solution Approach 1:
The patent replaces complex mechanical dispersion systems with a simpler interferometric system using tilted diffraction gratings and beam splitters. This substitution reduces device complexity while achieving high spectral resolution through the spatial heterodyne interference pattern, which can be processed computationally rather than requiring complex optical sorting mechanisms.
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 SHRS provides high spectral resolution, wide-area measurement capabilities, and high light throughput, enabling applications such as chemical process monitoring, planetary exploration, and biological tissue imaging, with the ability to integrate multiple spectrometers into a chemical process stream or send them to remotely located samples, while maintaining a small size and high performance.
Implementation Method 1
Light entering the SHS is split into two beams by the 50/50 beam splitter. The separated beams strike the tilted diffraction gratings, are diffracted back along the same direction, re-enter the beam splitter, and recombine.
Implementation Method 2
For any wavelength other than Littrow, the recombined light produces a crossed wave front, of which the crossing angle is wavenumber dependent, and produces an interference pattern at the interferometer output, which is the Fourier transform of the Raman spectrum.
Implementation Method 3
this overlap can be avoided by tilting one grating, producing a rotation of the fringe pattern clockwise for bands at wavenumbers below the Littrow wavelength and counter-clockwise for bands above Littrow.
Data Source
AI summary
The present subject matter is directed to a device for spectroscopy. The device includes an excitation source and a first spatial heterodyne spectrometer configured to receive wavelengths from the excitation source and filter the wavelengths to produce fringes on a sample. The device also includes a second heterodyne spectrometer configured to receive Raman wavelengths from the sample.