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Monday, 16 May 2011

DM: Tsuneto: Development of CEP-stabilized high power CPA/OPA lasers and direct generation of highly phase-matched isolated attosecond pulses

One of the most crucial issues for the present attophysics is to increase the pulse energy of isolated attosecond pulses (IAP.s). For this purpose, there are two crucial experimental challenges to demonstrate; one is to develop multi-mJ few cycle lasers with a stabilized carrier-envelope phase (CEP) and the other is to achieve the phase-matching highly between the few cycle pulses and high harmonics of them. In this talk, I will present our research activities on both challenges. First, I will present our recent results of RIKEN based on our TW-class 2-cycle laser system (5 fs, 780 nm, 5 mJ, 1 kHz). Recently, we have stabilized CEP of this system with two feedback loops and by blocking mechanical vibrations on the laser system thoroughly. Through the phase matching process, we could select the supercontinuum component of the harmonics without any use of bandpass filters such as Mo/Si mirrors. By using a heterodyne interferometry using mixed gases, we verified that we could select IAP directly. Second, I will briefly introduce our recent results at Imperial College London on constructing a CEP-stabilized high power OPA (optical parametric amplification) laser. CEP-stabilized seed pulses were generated using type II DFG of different frequency components of the supercontinuum generated with a hollow fiber compression technique, and the seed pulses were amplified by two-stage OPA.s. Final output pulses had a pulse energy of 500 μJ, pulse duration of 40fs, and tunable wavelength from 1300-1800 nm. As the first demonstration of this handmade laser, we could generate high harmonics up to 47th using a tube target filled with Xe gas.