Infrared Optical Parametric Chirped Pulse Amplifier for High Harmonic Generation

Abstract

Rapid advances in high-field physics achieved in recent years, most notably generation of isolated soft X-ray attosecond pulses, owe their success to the development of driver lasers with specific pulse properties. The latter include ultrahigh peak intensity, quasi-monocycle duration, and reliable control over the carrier-envelope phase (CEP) [1],[2]. Although the driver lasers currently employed in this research field operate nearly exclusively in the wavelength region of the Ti:sapphire gain (i.e. around 0.8 µm), a switching over to a longer, infrared (IR) wavelength would offer significant advantages. Because of the λ ² scaling of the ponderomotive energy, the intensity of IR pulses needed to attain emission at a given X-ray photon energy could be substantially lowered in comparison with the 0.8-µm case [3]–[5]. This is expected to be extraordinarily helpful for up-scaling the X-ray frequency, decreasing the duration of X-ray attosecond pulses by at least a factor of λ ^3/2, and suppressing undesired target preionization before the interaction with the strongest half-cycle of the laser pulse. From the standpoint of laser technology, the longer duration of the IR optical period reduces the number of cycles for a given pulse envelope and, therefore, relaxes the demand to the amplifier gain bandwidth, which in the case of 5-fs 0.8-µm pulses typically reaches the extreme > 100 THz.