ATTOSECOND OPTICS · Harnessing attosecond nonlinear optics for controlling and enhancing high harmonic generation and producing useful coherent x-rays on a tabletop

Attosecond nonlinear optics will be harnessed for increasing the efficiency and tunability of laser-driven x-rays through high harmonics generation. The process of high harmonic generation, which converts visible laser light into laser-like x-rays, facilitates new directions in science and technology. Examples include the production of attosecond pulses of light that allows direct investigation of the motions of electrons in atoms, molecules, and materials as well as the compact generation of x-rays for nano and bio imaging. However, for most applications, the generation of usable flux is, to date, limited to relatively long wavelengths (>10 nm) in which the upconversion process is rather benign and can be fully phase matched. At the foundation of this proposal are all-optical quasi-phase matching techniques, recently pioneered by the author during his post-doc in USA, which allows the holographic creation of nonlinear structures in the high harmonic generation process. Similarly to photonic structures for visible light, the optically induced nonlinear structures can be used for manipulating and enhancing the generated x-rays. New quasi-phase matching techniques will be developed and implemented for generating harmonics at 10-1 nm with high flux. Periodic structure with periodicity that varies according to the phase matching conditions of a given harmonic order will be used for generating coherent quasi-monochromatic x-rays while stochastic structures will be exploited for generating wideband x-rays. Longitudinally chirped periodic structures will be used for generating sub 100 attosecond pulses while transversely parabolic periodic structures will be exploited for focusing the generated beam at a required distance from the nonlinear medium. The proposed research will have important impact on the generation of compact and bright coherent x-rays for applications in materials and chemical dynamics, nanotechnology, microscopy, biology, and medicine.