Nonlinear optical properties of mask layer in super-RENS system

A super-resolution near-field structure (super-RENS) has an additional mask layer in the usual phase change optical disk. A thin layer of antimony (Sb) film or a silver oxide (AgOx) layer is used as a mask layer. By focusing a laser beam, a transparent aperture in the Sb layer and a light scattering center in the AgOx layer are formed transitionally, whose diameters are smaller than that of the laser beam spot. The changed portion can generate an intense optical near field and can be used to record and retrieve small marks beyond the diffraction limit. The nonlinear optical properties of Sb and AgOx films with protective layers were examined using a pulse laser. Optical switching, their time response and transient spectroscopic change were investigated. Light scattering property of AgOx film was also examined. A repeated optical switching action can only be realized if the illuminating spot size is confined to very small areas. Time response of Sb film shows first rise-up and then slow exponential decay. Time response of AgOx film shows more complicated decay than Sb film. Transmittance spectra just after the pump irradiation becomes flat over wide spectral range both in Sb and AgOx layers. Scattered light is extremely enhanced by increasing the input light power.