ИСТИНА

Nowadays mid-IR photonics is a rapidly developing area due to their inspiring horizons both in fundamental and practical areas. During the last decades the most prospective way to reach high peak powers in mid-IR is the usage of optical parametric chirped pulse amplification (OPCPA) concept [1,2,3]. The alternative way to build mid-IR high power laser system is using the relatively new transition metal-doped crystal Fe:ZnSe which emission bandwidth supports to 50 fs pulse duration. In our previous papers we have developed an approach for the creation of high-power femtosecond laser system based on chirp pulse amplification of mid-IR seed in optically pumped Fe:ZnSe gain medium [4]. The amplification of nanosecond and femtosecond pulses in Fe:ZnSe was investigated in [5] and [6] correspondingly with further enhancing of the energy extraction from the amplifier up to 1.2 mJ [7]. In this contribution, we present complete laser system, which is based on hybrid parametric and laser amplification and delivers 3.5 mJ 150 fs laser pulses centered at 4.4 um [8]. To the best of our knowledge, this is the first CPA system that operates at wavelengths longer than 2.5 um. To demonstrate the potential of the developed IR fs source we generate four-octave-spanning supercontinuum (SC) in xenon. Output beam from the system was focused by the CaF2 lens with focal length of 150 mm inside 8-cm-long gas chamber. We used only 2.5 mJ of the output energy in order to avoid self-phase modulation at the entrance of the 1-cm-thick CaF2 window. CaF2 lenses with 150 and 50 mm focal lengths were used to focus pump radiation and collimate generated supercontinuum (SC). Generated radiation was then directed into the scanning monochromator equipped with the set of diffraction gratings (150 – 3000 gr/mm) and detectors (PMT, Ge, PbSe and MG-32). We observed stable plasma channel and strong visible conical emission at 20 bar pressure. Generated supercontinuum covers the whole region from 350 nm to 5.5 um. We believe that careful adjustment of the pressure or/and cell length may also lead to filamentation assistant self-compression to few-cycle pulses.