In the first part of the talk a novel technique for the generation of intense few-cycle pulses is presented. Based on filamentation, an intense CEO-stabilized 43-fs laser pulse yields a supercontinuum, supporting 1.8 fs pulses, with a spectral range covering more than 600 THz. Chirped-mirror compression yields 5.7-fs pulses with 0.38 mJ energy in an excellent mode, with the CEO phase-lock being preserved. The second part of the talk will show that attosecond pulse trains (APTs) are a natural tool for controlling strong field processes, such as high order harmonic generation. By using them in combination with an intense infrared laser field, the timing of the APT with respect to the infrared (IR) laser field can be used to microscopically select a single quantum path contribution to a process that would otherwise consist of many interfering components. It is through this timing that we have predicted and recently confirmed control over the release of the electron into the continuum, its excursion inside the continuum and consequently influence the yield and coherence properties of the harmonics. We will present results from an initial proof-of-principle experiment where we see a clear enhancement of the harmonic yield in the photon spectrum at the cutoff region only when both the APT and the IR field are present.
ETH Zurich, Physics Department – Institute of Quantum Electronics