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We experimentally investigate the high-order harmonic generation in argon gas cell driven by a multi-cycle broadband infrared laser pulse from a tunable optical-parametric-amplifier (OPA) source. The generation of high-order harmonic continuum with the cut-off photon energy up to 110 eV is observed by tuning the chirp of the 800-nm laser pulse which pumps OPA source. The generation of harmonic continuum is understood in terms of the two-hump structure of the OPA output spectrum and the optimal relative phase of the two humps. The demonstrated scheme is of importance for the generation of extreme ultraviolet (XUV) continuum at higher photon energy region.

We demonstrate a 100 μJ

We demonstrate what we believe to be a novel tunable IR optical parametric amplifier (OPA) with the passively stabilized carrier-envelope phase (CEP), in which a hollow fiber is used to improve the output beam quality and to overcome the spatial chirp issue. Pumped by an 800 nm pump source, the output pulses are tunable from 1.2 to 2.4 microm with the CEP stabilization. The maximum output average energy can reach approximately (1.2 W/40 fs)/1 kHz with the total of (6.8 W/40 fs)/1 kHz pump energy. Further, the high-order harmonic generation driven by the tunable phase-stabilized OPA has been demonstrated.

This paper was presented at the SPIE conference indicated above but inadvertently published by SPIE subsequent to its publication in another journal (Optics Letters). The paper has therefore been withdrawn from the SPIE Proceedings by the author and the publisher. The journal paper can be accessed at http://dx.doi.org/10.1364/OL.34.002730.

We experimentally investigate the high harmonic generation (HHG) from CH4 molecules and Xe atoms in a two-color field (using the 800 nm laser and the tunable laser with the longer wavelength from 1500 nm to 1900 nm), and observe that the longer wavelength component can destructively suppress the HHG from CH4 molecules. By controlling the time delay between the two color laser pulses or tuning the laser intensity of the longer wavelength component, the suppressions of the HHG from CH4 molecules and the enhancements of the HHG from Xe atoms at the same laser condition are observed. The results indicate that the longer wavelength component around the molecular infrared absorption can suppress the molecular HHG process.

We experimentally investigate the wavelength effect on high-order harmonic generation (HHG) in CH(4) molecules and Xe atoms driven by a tunable infrared parametric source, and observe that the molecular HHG around the vibrational resonance is more sensitive to the driver wavelength than HHG from an atomic gas with comparable ionization potential. The results can be attributed to the light nuclear motion induced by the driving laser field, and it becomes possible to control the proton vibration in the molecular HHG by tuning the infrared wavelength of the driving laser.