  We report an ultrafast, parallel and beyond-the-master micro-patterning
technique for ultrathin (30 nm-400 nm) non-absorbing polymer films by
diffraction of a laser light through a two dimensional periodic aperture. The
redistribution of laser energy absorbed by the substrate causes
self-organization of polymer thin-film in the form of wrinkle like surface
relief structures caused by localized melting and freezing of the thin-film.
Unlike the conventional laser ablation and laser writing processes, low laser
fluence is employed to only passively swell the polymer as a pre-ablative
process without the loss of material, and without absorption/reaction with the
incident radiation. Self-organization in the thin polymer film aided by the
diffraction pattern produces micro-structures made up of thin raised lines.
These regular microstructures have far more complex morphologies than the mask
geometry and very narrow line widths that can be an order of magnitude smaller
than the openings in the mask. The microstructure morphology is easily
modulated by changing the film thickness, aperture size and geometry and by
changing the diffraction pattern, e.g., by changing the aperture-substrate
distance.
