Abstract
Spatial heterodyne Raman spectroscopy is a spectroscopic detection technique that is particularly suitable for Raman measurements. The spectral range of traditional spatial heterodyne Raman spectrometer (SHRS) is limited by its spectral resolution and the number of detector elements. We propose an SHRS with an echelle-mirror structure that employs multiple diffraction orders to achieve a broad spectral coverage and high spectral resolution simultaneously. This SHRS is used to obtain the Raman spectra of organic liquids, inorganic solid targets, and mixed targets. Observations of aqueous solutions, and minerals are presented. In addition, anti-Stokes Raman shifts are also presented. The proposed SHRS technique shows good performance for broadband, high-resolution Raman measurements.
Highlights
Raman spectroscopy is popular in material identification and analysis applications because it is nondestructive, requires no sample preparation, and allows for both organic and inorganic substances to be measured in a variety of states
Gomer et al outlined the proof of concept for an spatial heterodyne Raman spectrometer (SHRS) to perform Raman measurements [13]; Foster et al developed a standoff SHRS to make in situ observations of liquid samples to rapidly identify xylene, monoethylene glycol, triethylene glycol, methanol and compressor oil within a gas pipeline [14], while another SHRS was used to conduct transmission Raman measurements on paracetamol tablet samples [15]; Hu et al showed that an SHRS has the ability to investigate the liquid and solid targets [16,] and to obtain two-dimensional (2-D) spectra of analytes in containers [17] and the standoff Raman spectra of chemical warfare agents and simulants [18]; Egan et al proved that the SHRS can be used for Raman measurements to unambiguously identify minerals, organic compounds and biomarkers [19]
The Echelle grating-Mirror SHRS (EMSHRS) takes advantage of the multiple orders of the echelle grating to obtain a broad spectral range that meets the requirements of Raman detection
Summary
Raman spectroscopy is popular in material identification and analysis applications because it is nondestructive, requires no sample preparation, and allows for both organic and inorganic substances to be measured in a variety of states. The spatial heterodyne Raman spectrometer (SHRS) offers multiple advantages, including a large aperture, high light throughput, in a compact, rugged package without moving parts, and compatibility with both pulsed lasers and gated detectors [12]. The proposed EMSHRS is based on a Michelson interferometer, which is modified by replacing the mirror in one arm with an echelle grating This system takes advantage of the multiple diffraction orders and high diffraction efficiency of the echelle grating to obtain a broad spectral range without the need for a mixture of the different orders. The results from investigations of aqueous solutions, minerals and anti-Stokes Raman shifts are presented
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