The electromagnetic force from two interfering light beams on isotropic materials is derived for surface relief grating formation processes. The Navier-Stokes equation is solved for the electromagnetic force induced motion inside the “photoplasticized” amorphous azopolymer film. The predicted inscription rates and surface velocities in surface relief grating formation processes are consistent with the experimental evidences, indicating that the surface relief gratings on amorphous azopolymer films are formed by the electromagnetic force on the materials, under the condition of “photoplasticization” through sufficient trans-cis-trans isomerization cycling.

• Received 26 July 2005

DOI:https://doi.org/10.1103/PhysRevB.73.165204