Numerical Calculations on the Grating-Assisted Phase Matching Condition of High Harmonic Generation in Photonic Crystal Fiber

We numerically investigated the grating-assisted phase matching (GAPM) of high harmonic generation (HHG) from the interaction of intense femtosecond laser pulse and rare gas in hollow core photonic crystal fiber (HCPCF). Our results show that the GAPM of HHG in HCPCF is especially suitable for photon energies in the range of 100~1keV. The calculated modulation period for GAPM of HHG in HCPCF is on the order of micrometer or sub-micrometer. This makes it easy to implement the GAPM of HHG with a counter-propagating modulation laser light in HCPCF. The high harmonic conversion efficiency is expected to be dramatically improved for the longer interaction length provided by the very low loss of HCPCF.