Scientists from École Polytechnique in Palaiseau, France, have created nanometer-scale patterns in thin sol-gel films containing azobenzene moieties by using the light from a near-field optical probe to induce migration of the photosensitive molecules.

After absorbing a photon, the azobenzene molecule temporarily shifts to a different isomeric configuration. This change results in motion. As reported in the Dec. 31 issue of Applied Physics Letters, the team found that for far-field exposure -- 100 nm away or more -- lateral deformation of the gel occurs. In this case, the matter migrates away from the light's spot, in the direction of its polarization.

Near-field irradiation -- less than 10 nm away -- results in a protrusion from the gel's surface. The diameter of the protrusion is proportional to the probe's aperture, and its height is relative to the irradiation dose.

The researchers anticipate that such manipulation techniques may lead to high-density optical storage systems with capacities of at least 1 GB/cm².