engleski

Characterization of Laser-Produced Plasma by Cavity Ring-Down Spectroscopy

Laser-produced plasmas (LPP) offer a wide range of applications for which one needs to know the plasma content and dynamics. The most common techniques are optical emission spectroscopy, time resolved mass spectrometry, time resolved imaging etc. However such plasmas usually also contain non-excited neutrals. This points to the need of using some absorption based technique in order to obtain the complete picture about the plume. The Cavity Ring-Down Spectroscopy (CRDS) is the absorption technique based on the measurement of life-times of laser photons injected into a high finesse optical cavity. It offers advantages compared to classical absorption techniques and can easily reach ppb sensitivity. The basics of the CRDS technique will be described with emphasis on special features connected to the case of time changing absorption during the ringdown, as it exists in LPP. Some examples will be given on how to obtain data on atom/molecule column densities and their velocities. In addition, CRDS can be used as a tool for temporal and spatial mapping of the plasma plume. Advanced use of CRDS for LPP plume diagnostics will be discussed in respect to development of new laser sources such as supercontinuum lasers or femtosecond frequency combs.

laser produced plasma; cavity ringdown spectrosocopy

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