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Near infrared few-cycle pulses for high harmonic generation

We report on the development of tunable few-cycle pulses with central wavelengths from 1.6 um to 2 um. Theses pulses were used as a proof of principle for high harmonic generation in atomic and molecular targets. In order to generate such pulses we produced a filament in a 4 bar krypton cell. Spectral broadening by a factor of 2 to 3 of a 40 fs near infrared input pulse was achieved. The spectrally broadened output pulses were then compressed by fused silica plates down to the few-cycle regime close to the Fourier limit. The auto-correlation of these pulses revealed durations of about 3 cycles for all investigated central wavelengths. Pulses with a central wavelength of 1.7 um and up to 430 uJ energy per pulse were employed to generate high order harmonics in Xe, Ar and N2. Moving to near infrared few-cycle pulses opens the possibility to operate deeply in the non-perturbative regime with a Keldysh parameter smaller than 1. Hence, this source is suitable for the study of the non-adiabatic tunneling regime in most generating systems used for high order harmonic generation and attoscience.