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.Comment: 12 pages, 4 figure
