Repotenciamiento y optimización del funcionamiento de un equipo Gasmas (Gas in scattering media absorption spectroscopy) y consideraciones estadísticas de la propagación de la luz en el medio en dependencia de la geometría de incidencia

Abstract

The main purpose of this work was to rehabilitate a GASMAS setup (Gas in scattering media absorption spectroscopy) to being able of measuring molecular oxygen, and to additionally improving its operation capabilities by introducing the ability to measure the relative concentration of water. The equipment was tested separately for each case. Optimal operation conditions were determined. A MatLab code was written to automate the data acquisition from the digital oscilloscope to the computer. Additionally, we have studied the effect of the laser incidence geometry, at different angles, on the sample and its effects on the GASMAS signal. A situation in which lateral incidence as oppose to transmission or backscattering geometries is preferable in terms of sensitivity was determined. A theoretical and experimental research about light propagation in dispersive mediums was performed. The processing and experimental evaluation of images of dispersion profiles with different polarization states of the beam correlated with simulations, a random-walk model was used to simulate the photon propagation. Results show the pertinence of the underlying assumptions in terms of randomness and scattering mechanisms typical of the evaluation of the transmitted intensity in GASMAS. Finally, optimal instrumental, geometric and methodological conditions were determined that allow making an efficient application of the GASMAS technique to sequential measurement of molecular oxygen and water vapor in dispersive mediums.