Three-dimensional recording by femtosecond pulses in dielectrics

Fabrication and characteristics of two-dimensional (2D) and three-dimensional (3D) periodic structures, recorded in the bulk of SU8 photoresist film by multiple-beam interference is described. Multiple beams (up to nine.) were generated by a diffractive beam splitter. Recording was performed by ultrashort laser pulses with temporal width of 140 fs (FVWM) and central wavelength of 800 nm, derived from a Ti:sapphire laser. Intensity-dependent photomodification of the photoresist was due to single-photon as well as multi-photon (two and three) absorption. After the development, the exposed resist films contained free-standing 2D and 3D periodic dielectric structures with unexposed exposed regions removed by the development. Detailed examination of the samples has revealed close resemblance between their structure and the light intensity distributions in the multiple-beam interference. fields, expected from the numerical calculations. Quality of the samples recorded by a single-photon absorption was lower than that of that of other samples, in particular due to poor development quality. The microfabrication method used in this work appears to be a suitable for obtaining photonic crystal templates.