Modeling the short wavelength infrared laser radiance reflection on the sea surface.

The sea surface is a complex dynamic structure dependent on atmospheric conditions, and for which physical and chemical properties change from water to foam. Its roughness determines how the surface reflects, absorbs, and emits radiance, and depends on multiple parameters such as wind speed and direction, and foam and turbulence induced from natural waves or from object displacement. In this paper, a model description is given for laser reflection on the sea surface in open water driven by the wind.

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments.

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source.

Kilometer range filamentation.

We demonstrate for the first time the possibility to generate long plasma channels up to a distance of 1 km, using the terawatt femtosecond T&T laser facility. The plasma density was optimized by adjusting the chirp, the focusing and beam diameter. The interaction of filaments with transparent and opaque targets was studied.

Efficient spectral-step expansion of a filamenting laser pulse.

We report an efficient transfer of 800 nm energy into both the ultraviolet and the far infrared (IR) during the filamentation in air of an appropriately shaped laser pulse. The multiorder enhancement of the IR supercontinuum in the 3-5 μm atmospheric transmission windows was achieved thanks to spectral-step cascaded four-wave mixing occurring within the spectrum of the shaped femtosecond laser pulse. These results also point out the limit of the self-phase modulation model to explain the spectral broadening of a filamenting laser pulse.

Laser guiding of Tesla coil high voltage discharges.

We have investigated the guiding and triggering of discharges from a Tesla coil type 280 kHz AC high voltage source using filaments created by a femtosecond Terawatt laser pulse. Without the laser the discharges were maximum 30 cm long. With the laser straight, guided discharges up to 110 cm length were detected.