Berlin 2014 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 40: Ultrashort laser pulses I

Q 40.4: Vortrag

Donnerstag, 20. März 2014, 11:15–11:30, DO26 207

Direct generation of 7 fs white light pulses from bulk sapphire without external compression — •Emanuel Wittmann, Maximilian Bradler, and Eberhard Riedle — LS für BioMolekulare Optik, LMU München

Continuum generation in bulk material is a generally applicable method to broaden the spectrum of femtosecond pulses at a variety of repetition rates. It is driven with low µJ range pump pulses. Contrary to the continuum generated in microstructured fibers, the resulting spectrum is smooth and of equal spectral intensity over an octave [1]. The Fourier limit for a possible compression of, e.g., a 800 nm pumped continuum from sapphire, amounts to about 4 fs. Yet, no results have been published that come even close to this limit. In precise investigations of the continuum generation and propagation we now find that the inability to compress the continuum stems from the highly wavelength dependent effective generation locus and propagation. With this understanding, we revert to a 1 mm sapphire plate and optimize the generation onto the output face. The continuum is than imaged into the experiment or autocorrelator with an anastigmatic and achromatic combination of two spherical mirrors. As a result we find visible pulses as short as 7 fs without the use of any external compression scheme. This is quite similar to the celebrated filamentation experiment of Hauri et al. [2]. The broadband visible pulses can be ideally used for seeding noncollinear OPAs (NOPAs).

[1] C. P. Hauri, et al., Appl. Phys. B 79, 673 (2004).

[2] M. Bradler, P. Baum, E. Riedle, Appl. Phys. B 97, 561 (2009).