Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 54: Nano-optics of metallic and semiconducting nanostructures (experiments II)

O 54.12: Talk

Thursday, March 26, 2009, 17:45–18:00, SCH A216

Transform limited focusing of few cycle optical pulses using all-reflective optics — •Diyar Sadiq, Bjoern Piglosiewicz, Manfred Maschek, Wjatscheslaw Schmidt, Robert Pomraenke, Parinda Vasa, and Christoph Lienau — Institut für Physik, Carl von Ossietzsky Universität, 26129 Oldenburg, Germany

The availability of high-intensity few-cycle optical pulses from turn-key laser oscillators is important for various applications in the emerging field of extreme nonlinear optics. This requires focussing few-cycle pulses down to - or even beyond - the diffraction limit. Using conventional microscope objectives this is highly challenging due to their complex spatio-temporal dispersion properties. All-reflective objectives, minimizing chromatic dispersion, are expected to have much more favorable focussing characteristics. So far, however, little is known about the spatio-temporal distribution of electromagnetic fields of few-cycle pulses in the focus of such an all-reflective-objective. Here, we demonstrate focussing 6-fs, 2.25-cyle optical pulses from an 80-MHz repetition rate Ti-sapphire oscillator down to a diffraction-limited spot size of less than 1 µm while maintaining the pulse duration. Three-dimensional mapping of the spatial intensity profile near the focus is performed using a scanning near-field optical microscope. The time profile of the focussed pulse is characterizing by interferometric autocorrelation measurements using second harmonic generation or - with sub-100-nm spatial resolution - using electron generation at sharp metallic tips. Progress towards direct space- and time-resolved electric field measurements will be reported.