A High Spatial and Depth Resolution Deep-UV 266 nm Wavelength Laser-Based Integrated LIBS, Fluorescence, and Raman...

A high spatial and depth resolution deep-ultraviolet (UV) 266 nm wavelength laser-based integrated laser-induced breakdown spectroscopy (LIBS), fluorescence, and Raman (LFR) system was developed for qualitatively probing lunar and planetary simulants and geological materials. The LFR system involves the use of a simple, low-weight, and compact LFR optical head (6 cm × 3 cm × 5 cm) consisting of common optics (filters, lens, and optical fibers) while being supported by an external single deep-UV pulsed laser source at 266 nm wavelength and a shared spectrometer for multifunctional Raman, fluorescence, and LIBS spectroscopy. A spatial resolution of about 15 μm was achieved and can be further decreased to under a μm. The submicron depth resolution was achieved by the 266 nm wavelength laser ablation process and can be further improved to tens of nanometers. The performance of the integrated LFR system was evaluated by probing both standard materials (organic and inorganic) as well as previously characterized simulants and geological materials, which predominantly consisted of mixtures of silicates and oxides of various metals. The obtained LIBS spectra agreed well with the literature, and no significant spatial and depth variation in composition was noted. The optical head was correctly able to obtain good Raman signatures from a range of materials, including organic (alcohol, alkanes, amino acids, and polymer) and inorganic species (sulfates, carbonates), such as water, selenite, and calcite. Analysis of the LIBS spectra correctly revealed the presence of major elements, such as Mg, Si, Fe, Al, Ca, Mn, and Ti, in the basalt, gneiss, meteorite, and simulants. This work establishes a foundation for developing single laser-spectrometer-based compact multifunctional deep-UV spectroscopic systems performing both Raman and LIBS alongside fluorescence, paving the way for further advancements toward miniaturization.