Abstract

Thin-film microoptical arrays arc promising tools for ultrashort-pulse laser beam shaping and characterization. Short optical path lengths, minimum spectral dispersion, low absorption and broadband transmission are advantageous features for the handling of high-power few-cycle pulses. The beam shaping in space, time and spectrum is of great practical interest for many applications (multiphoton excitation, material processing, acceleration, atom guiding, measurement techniques) and also relevant for an evaluation of damage risks. In our experiments, we investigated three different kinds of interference phenomena: (a) free-space interference of converging beams (quasi-Bessel beams with extended focal zones and transversal fringes), (b) self-imaging of array structures (Talbot effect with regular intensity patterns), (c) interference caused by internal reflectance of spatially variable Fabry-Perot etalons (Newton rings). To shape the beam of a home-made Ti:Sa laser, low-loss refractive thin-film elements have been used (SiO₂, TiO₂ on quartz substrates). Sag heights < 15µm, thickness-to-period-ratios of < 0.02 and single element diameters of 20...700 µm have been realized.

© 2000 IEEE