München 2004 – scientific programme

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Q: Quantenoptik und Photonik

Q 10: Ultrakurze Lichtimpulse: Röntgenpulse und Kernphysik

Q 10.4: Talk

Monday, March 22, 2004, 17:15–17:30, HS 223

Temporal pulse cleaning: way to pre-pulse free interaction — •Enrico Risse, Mikhail Kalashnikov, Horst Schoennagel, and Wolfgang Sandner — Max-Born-Institut, Max-Born-Strasse 2a, D-12489 Berlin

Relatively high amplified spontaneous emission of a high power Ti:sapphire laser is one of the main drawbacks. Typically refocusing of the energetic pulse of a modern Ti:sapphire laser to intensity exceeding 10 20 W/cm2 will result in ASE and pre-pulse intensity higher than 10 14 W/cm2. The low energy of the master oscillator pulse, losses in the stretcher and introduction of means for spectral phase correction results in a low starting signal-noise ratio. Increasing of the injected energy and/or realization of a double-CPA system with intermediate recompression and nonlinear subtraction of the ASE pedestal and pre-pulses are the possible solutions of the problem. Different schemes of nonlinear cleaning including Sagnac interferometer, nonlinear absorber, rotation of polarization ellipticity (RPE) were experimentally tested. The Sagnac interferometer was found to be very unstable concerning the mode structure of the incident laser beam. For the RPE we developed a multipass cavity and realized up to 6 passes. Energy ratio between the clean and residual pulse was optimized by tuning of the pulse duration and amount of passes. Up to 0.6 conversion was achieved with a slightly stretched pulse. The system delivers perfect near-field beam distribution. We observed additionally strong modification of near field beam distribution depending on focal intensity.