Peter Baum, Stefan Lochbrunner, Markus Breuer

Generation of sub-10 femtosecond optical pulses NOPAs are convenient sources of tunable visible pulses with durations well below 20 fs. Although more broadband spectra can quite easily be generated, the presence of higher order chirp limits the pulse duration, depending on wavelength, to about 10-20 fs. For the generation of even shorter pulses with durations well below 10 fs three issues are essential: full pulse characterization, to understand and control the compression. generation of a broadband coherent spectrum, to have a short Fourier limit. adaptive pulse compression... Tunable spectra with an appropriate spectral width can be generated by strechting the pump pulse in a NOPA (chirped optical parametric amplification). From our ZAP-SPIDER measurements we learn that the chirp has almost only "smooth" (i.e. low-order) contributions. This opens up the route to a simple and flexible way to control the spectral phase directly in the existing prism compressor setup. Adaptive pulse compression with a deformable mirror To adaptively control the spectral phase of the pulses they are sent into a standard prism compressor. An electrostatically deformable membrane mirror with 19 segments is used as end mirror. By changing the voltages applied to the segments the membrane deforms and the path lengths for various spectral components change accordingly. Thereby phase shifts are induced and the chirp of the pulses can be controlled in a flexible way. Compression of UV pulses The compression of UV pulses is even more challenging. With achromatic phase matching we were able to generate spectra that can support 3 fs pulses. So far we were able to compress the pulses to 7 fs with a combination of CaF2 prsims and a Al-coated deformable mirror. Further progress is expected from newly available Brewster chirped mirrors.   Related Publications:

"Achromatic second harmonic generation: tunable ultraviolet pulses with sub-10 fs duration" P. Baum, S. Lochbrunner, and E. Riedle Ultrafast Phenomena XIV, T. Kobayashi, T. Okada, T. Kobayashi, K. Nelson, S. De Silvestri, eds. (Springer-Verlag, Berlin, 2005), 79 - 81 Details "Generation of tunable 7-fs ultraviolet pulses: achromatic phase matching and chirp management" P. Baum, S. Lochbrunner, and E. Riedle Appl. Phys. B 79, 1027 - 1032 (2004) Details "Tunable sub-10-fs ultraviolet pulses generated by achromatic frequency doubling" Peter Baum, Stefan Lochbrunner, and Eberhard Riedle Opt. Lett. 29, 1686 - 1688 (2004) Details "Widely tunable sub-30 fs ultraviolet pulses by chirped sum frequency mixing" Ida Z. Kozma, Peter Baum, Stefan Lochbrunner and Eberhard Riedle Opt. Express 11, 3110 - 3115 (2003) Details "12-fs pulses from a continuous-wave-pumped 200 nJ Ti:sapphire amplifier at a variable repetition rate as high as 4 MHz" R. Huber, F. Adler, A. Leitenstorfer, M. Beutter, P. Baum, and E. Riedle Opt. Lett. 28, 2118 - 2120 (2003) Details "Real-time characterization and optimal phase control of tunable visible pulses with a flexible compressor" P. Baum, S. Lochbrunner, L. Gallmann, G. Steinmeyer, U. Keller, E. Riedle Appl. Phys. B 74 [Suppl.], S219 - S224 (2002) Details