Photoresponsive polymers for topographic simulation of the optical near-field of a nanometer sized gold tip in a highly focused laser beam

Abstract

The local perturbation of a diffraction-limited spot by a nanometer sized gold tip in a popular apertureless scanning near-field optical microscopy (ASNOM) configuration is reproduced through topography changes in a photoresponsive polymer. Our method relies on the observation of the photochemical migration of azobenzene molecules grafted to a polymer placed beneath the tip. A local molecular displacement has been shown to be activated by a gold tip as a consequence of the lateral surface charge density present at the edges of the tip's end, resulting from a strong near-field depolarization predicted by theory.

Azopolymer‐based micro‐ and nanopatterning for photonic applications

“…In context of near‐field optics, azopolymers have been used to visualize the optical‐field distributions at the vicinity of probe tips of near‐field optical microscopes, and to map the optical response of surface‐mounted copper nanoislands . As an example, Figure (a,b) display the surface deformation of an initially flat film irradiated through a metal‐coated tapered optical fiber .…”

Laser nanofabrication in photoresists and azopolymers

“…The basic phenomena discovered in the field, including photoinduced mass movement of polymers, are summarized in a book that we edited in 2002 . Photoinduced patterns of surface deformations in azobenzene‐containing polymer films have attracted much attention because of possible applications in optical data storage and in micro‐/nanofabrication, and it is well known that such patterns reflect the state of the incident light polarization and the light‐intensity distribution . The photoinduced patterns are due to light‐induced mass movement of the polymer chains which in turn is triggered by the photoisomerization of the azochromophores.…”

Longitudinal anisotropy of the photoinduced molecular migration in azobenzene polymer films

“…Photoinduced mass transport in thin polymer films containing azobenzene chromophores have been extensively studied for their applications in optical data storage, 1,2 self-developing functional optical elements, 3,4 and optical near-field investigations. 5,6 Surface relief is the result of large-scale migration of the polymer backbone caused by the repetitive cycling of trans-cis photoisomerization of the aromatic group. 7 It was found that a variation of the spatial distribution of the light intensity involving lateral field components was necessary to optically induce surface modulation.…”