Abstract

Intense ultrashort IR and mid-IR sources have significant advantages in extending the high harmonic (HH) cutoffs from the extreme ultraviolet to the soft x-ray region. The highest cutoff energy of 1.6 keV was achieved by a high-energy mid-IR source [1]. The carrier-envelope phase (CEP) -dependent HHs beyond the carbon K edge was reported by a few-cycle IR source [2]. These few-cycle IR light sources is promising to open a route to ultrafast spectroscopy in the soft-X-ray region on the attosecond time scale. However, increasing the photon flux of soft X-ray HHs is crucial to realize ultrafast photoemission and element-specific absorption spectroscopy.

© 2015 IEEE