| Abstract [eng] |
Generation and Compression of Few Optical Cycle Pulses in the Mid-infrared Spectral Range Generation of few optical cycle pulses in the mid-infrared is mainly based on second order nonlinear effects such as difference frequency generation and optical parametric amplification. However, the amplification bandwidth of the parametric amplifier is too narrow to support the spectrum of few optical cycle pulses. Therefore, a technique of pulse self-compression during the nonlinear propagation in transparent dielectric media is employed. Such self-compression phenomenon stems from an interplay between the effects of self phase modulation and anomalous group velocity dispersion of the material before the onset of catastrophic self-focusing and beam filamentation. The main objective of this work was to develop a Ti:sapphire laser system based parametric mid-infrared few optical cycle pulse source and to demonstrate the possibility of pulse self-compression exploiting the nonlinear propagation process in a transparent solid state medium featuring anomalous group velocity dispersion. During this work, a compact laser source was developed, providing sub-3 optical cycle pulses with energy of 14-30 µJ in the 3-4 µm spectral range. The source employed difference frequency generation between the signal and idler waves from a near-infrared β-BBO optical parametric amplifier in a KTA crystal and a subsequent broadband parametric amplification of mid-infrared pulses in an optical parametric amplifier. Finally, the amplified pulses were self-compressed during lossless nonlinear propagation in transparent wide energy bandgap media exhibiting anomalous group velocity dispersion. The achieved energy transmission of the nonlinear propagation in YAG, CaF2 and BaF2 plates exceeded 90% as pulses were self-compressed down to sub-3 optical cycles. Even shorter pulse durations were observed during the filamentation regime as the duration of central peak of 3.5 µm pulses corresponded to 1.6 optical cycles, although the energy transmission decreased to 66%. The applicability of the developed laser source for various studies of ultrafast light-matter interactions in both dielectric and semiconductor media was shown by generating an ultrabroadband more than 3 octave spanning supercontinuum in CaF2 and BaF2 plates. |
