February 26 , 2007

Attosecond Nonlinear Optics

Oren Cohen

JILA, University of Colorado at Boulder

The conversion of laser light into coherent soft x-rays using the process of high-order harmonic generation (HHG) is the best example of a complex process where attosecond time-scale dynamics can be coherently manipulated - representing the fastest technology devised to date. In HHG, an intense driving laser first ionizes an electron. The electron then oscillates in the continuum, driven by the laser field, before finally recombining with the parent ion, liberating its excess energy as a high energy photon. In this talk, I will present exciting new approaches for manipulating the phase of the recolliding electron, and as a result, the phase of the emitted harmonics. Applications of this control scheme include (1) selecting which of the electronic quantum trajectories contributes to the HHG process, (2) probing of the coherent buildup of the harmonic waves, and (3) selectively correcting the phase mismatch between the driving laser and a high-order harmonic, hence, significantly increasing the conversion efficiency. This approach shows great promise for overcoming the grand challenge of correcting the large and dynamically changing phase mismatch conditions in extremely high-order harmonic generation, enabling applications in x-ray nonlinear optics as well as ultrafast bio-, nano-, and molecular probing on attosecond time scales.