Raman and UVN+LWIR LIBS detection system for in-situ surface chemical identification

Comparative Long-Wave Infrared Laser-Induced Breakdown Spectroscopy Employing 1-D and 2-D Focal Plane Array Detectors

“…The details of the experimental setup, a lab-based bench-top simultaneous UV/Vis/NIR + LWIR LIBS prototype spectrometer, and calibration procedures have been discussed in detail in previous studies [ 2 , 4 ]. This bench-top detection system can remotely probe the target from a distance from 0.1 up to 6 m utilizing a compact Q-switch Nd:YAG laser excited (1064 nm), fixed grating and mercury–cadmium–telluride (MCT) linear detector array (1 × 332 detector elements, 50 × 50 µm pitch size, integrated with a readout integrated circuit (ROIC)) based spectrometer for LWIR LIBS measurements, and a grating + CCD-based UV/Vis/NIR spectrometer covering 200–1000 nm for UV/Vis/NIR LIBS measurements.…”

“…These spectral signatures can be readily used for target identification and characterization. In this study (as shown in Figure 1 ), a two-dimensional (2-D) MCT focal plane array (FPA) detector (PhaseTech MCT 2-D array with a pixel format of 128 × 128 and 40 × 40 µm pitch size, integrated with ROIC) was tested for the first time in LWIR LIBS measurements, besides the typical linear MCT array detector used in previous studies and in Section 3.1 and Section 3.2 of the current work [ 1 , 2 , 3 , 4 , 8 , 9 , 10 ]. Sharing the same excitation and collection optics setup of the bench-top detection system ( Figure 1 ), the spectral resolutions for both 1-D and 2-D detection measurements were about 76 nm [ 3 ].…”

“…For example, ultraviolet Raman spectroscopy demonstrates potential for non-contact standoff detection of hazardous materials on surfaces, but some great challenges remain. For remote optical reflectance techniques, such as Raman spectroscopy, the spectral signature signals are usually very weak and the accuracy of the surface contamination measurements are frequently influenced by the shape, roughness, composition irregularity of the target surfaces, and complex background emissions (e.g., fluoresce from the surface) [ 2 ]. An ideal optical technique in the reconnaissance mission should have intense signal responses and be affected very little by the surface shape, roughness, and composition irregularity.…”

“…Those molecular gases in the vicinity of the vapor–plasma plume were thermally excited by the hot plasma and emitted vibration–rotation spectral signatures in the mid-IR (MWIR to LWIR) region which could be readily used for molecular identification. Based on those discoveries, an innovative LWIR LIBS spectroscopy, sometimes referred to as laser-induced thermal emission (LITE), was recently developed [ 1 , 2 , 3 , 4 ]. In LWIR LIBS, the molecular structures of constituents are revealed by spectrally analyzing the emission profile from a laser-induced plasma generated on the target surface using mid-IR spectroscopy.…”

“…In LWIR LIBS, the molecular structures of constituents are revealed by spectrally analyzing the emission profile from a laser-induced plasma generated on the target surface using mid-IR spectroscopy. To the best of our knowledge, LWIR LIBS is, to-date, the only vibrational–rotational mid-IR emission spectroscopy technique that offers the same instrumental and analytical advantages of both conventional UV/Vis/NIR LIBS and Raman spectroscopy in on-site field applications [ 1 , 2 , 3 , 4 , 9 ]. One of the greatest advantages of this new spectroscopy is its simplicity to pair with a UV/Vis/NIR LIBS spectrometer.…”