Imprinting the optical near field of microstructures with nanometer resolution

Abstract

An experimental method to directly image with nanometer spatial resolution complex 2D near-field intensity distributions underneath the scattering particle by imprinting a 2D pattern in thin photosensitive films, was demonstrated. The sputter-deposited samples consisted of 40-nm-thick, face-centered-cubic polycrystalline Ge2Sb2Te5 films on Si [001] wafers covered by a 10-nm-thick amorphous SiO2 buffer Layer. Spherical silica particles with a polydispersity of <10% in diameter, a measured refractive index of 1.44 at 589 nm, stored in isopropanol, were deposited on the substrate by means of spin coating. Laser irradiation was performed in air using a regeneratively amplified Ti:sapphire laser system. The sample was mounted on a movable table and observed in situ with a home-built microscope based on a microscope objective and a tube lens, equipped with a 12 bit charge-coupled device (CCD) camera. The light polarization is found to have a strong influence on the imprinted pattern. © 2009 Wiley-VCH Verlag GmbH & Co.