Exploiting optical near-fields for phase switching and nanopatterning

Abstract

We report a novel technique for exploiting optical near-fields of dielectric micro- and nanospheres upon illumination with short laser pulses for phase switching in Ge2Sb2Te5 films. The complex intensity distribution of the optical nearfield at the crystalline film surface is imprinted and leaves behind a characteristic amorphous fingerprint, which can be read out with optical microscopy, AFM and field emission SEM. We achieve full control over the resulting patterns by playing with the illumination conditions (laser wavelength, angle of incidence, polarization) and the size and arrangement of the particles. The experimental results are well described by a model based on Mie scattering theory solving Maxwell’s equations. We demonstrate that a written pattern can be erased also by near-fields and that erased patterns can be recovered by adjusting the light intensity. The influence of pulse duration and light wavelength on the minimum recordable features size and surface roughness of the pattern is explored. Minimum features with sizes well below 200 nm can be written, which are down scaleable by reducing pulse duration and wavelength.