Calculation of the spatial resolution in two-photon absorption spectroscopy applied to plasma diagnosis

We report a detailed characterization of the spatial resolution provided by two-photon absorption spectroscopy suited for plasma diagnosis via the 1S-2S transition of atomic hydrogen for optogalvanic detection and laser induced fluorescence (LIF). A precise knowledge of the spatial resolution is cru...

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Bibliographic Details
Published in:Journal of applied physics 2014-10, Vol.116 (13)
Main Authors: Garcia-Lechuga, M., Fuentes, L. M., Grützmacher, K., Pérez, C., de la Rosa, M. I.
Format: Article
Language:English
Subjects:
ABSORPTION
ABSORPTION SPECTROSCOPY
ACCOUNTING
Applied physics
CAMERAS
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
DECAY
Decay rate
DETECTION
Diagnosis
DISTRIBUTION
ENERGY-LEVEL TRANSITIONS
EXCITATION
FLUORESCENCE
FOURIER TRANSFORMATION
Fourier transforms
HYDROGEN
Ionization
Irradiance
Laser beams
Laser induced fluorescence
LASER RADIATION
Lasers
Mathematical analysis
Photon absorption
PHOTONS
PLASMA DIAGNOSTICS
RADIANT FLUX DENSITY
SATURATION
SPATIAL RESOLUTION
Spectrum analysis
THREE-DIMENSIONAL CALCULATIONS
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Summary:We report a detailed characterization of the spatial resolution provided by two-photon absorption spectroscopy suited for plasma diagnosis via the 1S-2S transition of atomic hydrogen for optogalvanic detection and laser induced fluorescence (LIF). A precise knowledge of the spatial resolution is crucial for a correct interpretation of measurements, if the plasma parameters to be analysed undergo strong spatial variations. The present study is based on a novel approach which provides a reliable and realistic determination of the spatial resolution. Measured irradiance distribution of laser beam waists in the overlap volume, provided by a high resolution UV camera, are employed to resolve coupled rate equations accounting for two-photon excitation, fluorescence decay and ionization. The resulting three-dimensional yield distributions reveal in detail the spatial resolution for optogalvanic and LIF detection and related saturation due to depletion. Two-photon absorption profiles broader than the Fourier transform-limited laser bandwidth are also incorporated in the calculations. The approach allows an accurate analysis of the spatial resolution present in recent and future measurements.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4896497