Plume dynamics of a laser produced plasma from a dot target

Abstract

To generate a plasma light source with a small spot size by reducing the expansion of the plasma plume, we studied the plume expansion dynamics of a plasma generated from a dot target that consisted of a photoresist with a hole coated on a pure Al plate. A time-resolved ultraviolet (UV) image of the plasma plume and a UV spectrometer were used to study the expansion of the plasma plume produced from a dot target and from an Al plate target. The measurements of the plume size from the emission of Al II ions showed that due to the strong collision between the core Al plasma and the plasma generate from the outer part of the dot, the expansion speed in the lateral direction was reduced to 70 % that of the plasma generated from the pure Al plate. However, for the case of the emission from neutral Al atoms, the plume sizes of the two targets were almost the same because of the weak collision between the Al atoms and the surrounding plasmas. Thus, these collisional effects in the plasma produced from a dot target can reduce the size of the core plasma ion and can be used to generate a small-spot-size laser plasma light source.