title: 2D plasmonic and diffractive structures with sharp features by UV laser patterning.
abstract: The  aim of this work is to produce 2D plasmonic and diffractive structures in Ag films with sharp features for which both a deeper understanding of laser induced transformation upon modulated laser intensity and a correlation between structural and optical properties are required. We compare results obtained by exposing silver films to an excimer laser operating at 193 nm whose intensity is either modulated or homogeneous. In all cases, one laser exposure is enough to break the film into nanoparticles (NPs). The use of the modulated beam intensity leads to diffractive 2D patterns that are formed by rectangular regions of untransformed material surrounded by transformed regions covered by NPs. The former have sharp edges that are consistent with the absence of significant mass transport that is discussed in terms of the thermal gradient induced. The latter contain NPs whose diameter increases as the initial film effective thickness increases. The surface plasmons associated with the NPs in the transformed regions dominate the reflectivity spectrum and the 2D array formed by the untransformed regions is responsible for the diffractive properties. Evidence for spinodal dewetting is only observed in our case for the steep gradient conditions achieved at the border of the homogeneously irradiated regions.
authors: Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, E-28006 Madrid, Spain. rpelaez@io.cfmac.csic.es
authors: R J
authors: RJ
authors: Peláez
authors: C N
authors: CN
authors: Afonso
authors: J
authors: J
authors: Bulíř
authors: M
authors: M
authors: Novotný
authors: J
authors: J
authors: Lančok
authors: K
authors: K
authors: Piksová