Abstract

Elementary volume phase holograms can be recorded in poly(methyl methacrylate) doped with a photoinitiator using a holographic two-beam set-up. The photopolymerization process of the residual monomers in the polymer matrix turns out to be inherently non-linear. Consequently, illumination with a sinusoidal light intensity pattern results not only in a grating with the fundamental spatial frequency but also with higher harmonics. As the absorption of the photodoped material steeply rises for wavelengths below 320 nm, structures with periods below about 105 nm cannot be read out by light diffraction in Bragg geometry, the limit for Laue geometry is even 160 nm. This poses the following question: Can we induce gratings by light which are below the optical resolution limit by the non-linear recording mechanism and how can we prove it?

© 1998 IEEE