Miniature spatial heterodyne spectrometer for remote laser induced breakdown and Raman spectroscopy using Fresnel collection optics

Highlights: • A remote LIBS/Raman spatial heterodyne spectrometer with a 100-mm diameter Fresnel lens as the collection optic is described. • 10 m standoff spectra of various samples are compared to those measured with a 100-mm aperture Questar long-range microscope. • The overall quality of the spectra as indicated by fringe visibility in the interferograms is the same using each lens. • Spectral intensity is reduced a factor of ~4 for the Fresnel lens, likely due to Fresnel losses and aberrations. • For applications with size and weight restrictions Fresnel optics could be a viable option to standard optics. A combined laser induced breakdown (LIBS) and Raman, spatial heterodyne spectrometer (SHLS/SHRS) is described for remote measurements using Fresnel collection optics. The spatial heterodyne LIBS and Raman spectrometer (SHLS and SHRS) is based on a fixed diffraction grating interferometer with no moving parts that offers a very large field of view, high light throughput, and high spectral resolution in a small package. The field of view of the SHS spectrometer is ~1° making it very forgiving of collection optics alignment and image quality for remote LIBS and Raman measurements. In the SHLS/SHRS system described here, a ~100-mm diameter, f/1.25 Fresnel lens used for light collection is compared to a high quality ~100-mm aperture Questar long distance microscope. LIBS and Raman measurements were made at 10 m for a variety of organic and mineral samples including materials from deep ocean hydrothermal vents.