Extreme nonlinear optics: attosecond photonics at short wavelengths

We discuss coherent up-conversion of near-infrared femtosecond laser light into the extreme ultraviolet and soft-X-ray regions of the spectrum using the process of high-harmonic generation. We show that by using concepts from visible wavelength photonics, it is now possible to extend nonlinear optics well into the X-ray region of the spectrum. By manipulating the dynamics of the high harmonic process using optimized waveguide structures and pulse shapes, and on attosecond timescales, we can control the energy of the emitted photons, as well as increase the efficiency of the up-conversion process. Use of these optimized waveguide structures and pulse shapes can also improve the spatial and temporal coherence of the light. This work demonstrates that sophisticated concepts from nonlinear-optical photonics and coherent control can be applied to "extreme" nonlinear optics.