Pure optical and reversible optically driven nanowriting of azobenzene block copolymers

We report on pure optical nanowriting in the near-field of spin-coated films of a specifically synthesized azobenzene-containing block copolymer. Writing is accomplished by linear polarized blue laser radiation, which is efficiently absorbed by the material, and readout is based on polarization-modulation of red laser radiation, which is practically unabsorbed. Purely optical, stable, and reversible modifications are observed at the 100 nm scale. Remarkably, they are not accompanied by any observable topographical change. We attribute the result to the use of a small azobenzene content (3% mol) and to the block architecture of the material.