| The main goal of the research is focused on the exploitation of diode lasers for several applications involving photon detection, high resolution spectroscopy and imaging of selected species in laser induced plasmas. Laser Induced Breakdown Spectroscopy (LIBS) is commanding much attention as an atomic emission spectroscopy technique due to its multiple attractive features. Much effort in the LIBS community has been, and still is directed toward the understanding of plasma fundamentals. Understandably, much information remains to be gathered in order to fully comprehend the laser-sample interaction. Of all the diagnostic techniques applied to plasmas and extensively described in the literature, absorption spectroscopy seems to be receiving comparatively less attention. In this work, we describe the use of selective absorption methods to follow the evolution of the plasma in time, and as a consequence, to better understand the temporal and spatial evolution of the different populations involved. The temporal behavior of a specific transition can be followed by measurements with a Photomultiplier Tube (PMT) and line shapes can be evaluated by scanning the diode laser. In spectrochemical analysis, line shapes plays a major role in the understanding of spectral interferences, plasma conditions and behavior of analytical applications. By spatially expanding the laser probe beam, the temporal and spatial evolution can be followed with a gated Intensified Charge-Coupled Device (ICCD), consequently assessing the studied species' homogeneity within the plasma plume.;Cesium atomic vapor filters or detectors have been a primary focus of this work as they demonstrate the potential to excel both in terms of spectral resolution and sensitivity. Atomic vapor detectors have a spectral resolution that is governed by the properties of the atomic vapor used as the sensing element, while maintaining the same value of the luminosity. Cesium vapor cells have been extensively investigated because of cesium's high number density at low temperature and its strong resonance transition in the near-infrared at 852nm (62S1/2 → 62P 3/2). A promising fluorescence scheme for cesium has been demonstrated here that includes a single transition at 852nm and fluorescence detection at 894nm (62P1/2 ↔ 62S 1/2). For efficient detection, a rapid fine-structure mixing (62P3/2 ↔ 62P1/2) is required and is provided by the presence of ethane in the cell. The absorption properties of this cell are reported as well as its potential application to a selected analytical problem such as the detection of Raman photons. |
