Anomalous infrared conical emission during ordered multifilamentation in gases.

We demonstrate that amplitude modulation of a high-peak-power femtosecond laser pulse allows to change fundamentally the frequency-angular structure (FAS) of the supercontinuum formed during the filamentation in both molecular and atomic gases. Particularly, modulation with a 4-hole mask forms an inverted pattern of conical emission (CE) with its predominance in the Stokes wing of the pulse spectrum. We explain this phenomenon as a joint effect of self-phase modulation and temporal pulse splitting of interfering beamlets formed by the modulating mask.

Robust multifilament arrays in air by Dammann grating.

We compare transverse structure evolution and energy deposition into the medium within focused multifilament arrays created using two different types of diffraction optical elements (DOEs): TEM phase plate and a Dammann grating. We show that the employment of the Dammann grating provides a robust way to create regular multifilament arrays, which is far less dependent on laser beam quality than one using the phase plate.

Transient optical non-linearity in p-Si induced by a few cycle extreme THz field.

We study the impact of a few cycle extreme terahertz (THz) radiation (the field strength E ∼1-15 MV/cm is well above the DC-field breakdown threshold) on a p-doped Si wafer. Pump-probe measurements of the second harmonic of a weak infrared probe were done at different THz field strengths. The second harmonic yield has an unusual temporal behavior and does not follow the common instantaneous response, ∝TH2.

Postfilament supercontinuum on 100 m path in air.

Pulses at 744 nm with 90 fs duration, 6 mJ energy, and a weakly divergent wavefront propagate for more than 100 m and generate a filament followed by an unprecedently long high intensity (≥1/) light channel. Over a 20 m long sub-section of this channel, the pulse energy is transferred continuously to the infrared wing, forming spectral humps that extend up to 850 nm. From 3D+time carrier-resolved simulations of 100 m pulse propagation, we show that spectral humps indicate the formation of a train of femtosecond pulses appearing at a predictable position in the propagation path.

Hybrid stimulated Raman scattering-two-plasmon decay instability and 3/2 harmonic in steep-gradient femtosecond plasmas.

We numerically study interaction of a very intense (I∼10^{17} to 5×10^{19}W/cm^{2}) femtosecond obliquely incident p-polarized laser pulse with a steep-gradient (L∼λ) plasma, i.e., within the conditions typical for modern experiments.