Three-dimensional recording by femtosecond pulses in polymer materials

Fabrication and characteristics of two-dimensional (2D) and three-dimensional (3D) periodic structures, recorded inside the bulk of negative SU8 photoresist film by multiple-beam interference are reported. The recording was performed by ultrashort laser pulses of 150 fs duration with central wavelength of 800 nm, multiple beams were generated using a diffractive beam splitter. Intensity-dependent photomodification of the photoresist was initiated by multi-photon absorption. The development process removed the exposed regions of resist film, leaving free-standing 2D and 3D periodic dielectric structures. Detailed examination of the samples is presented, which reveals close resemblance between the features of the fabricated structures, and those of the light intensity distributions in the multiple-beam interference fields. The microfabrication method used is demonstrated to be suitable for obtaining of photonic crystal templates. Phase control of the constituent beams allowed to monitor and control the light interference pattern to be recorded. Possibility to record the diamond lattice using this method is examined and discussed.