Demonstration of long-lived high power optical waveguides in air

Quantum Control of Molecular Gas Hydrodynamics

“…Moreover, we show that it is possible to deplete a population of rotationally excited molecules before the wavepacket collisionally decoheres, suppressing gas heating. These results point to new ways of precisely controlling gas density profiles in atmospheric propagation [7], and have practical implications for schemes using pulse trains to enhance supercontinuum generation, filament length and plasma density [13,14], and THz amplification [11]. Other novel extensions are also suggested.…”

“…Significant hydrodynamic perturbation of solids, liquids, and non-dilute gases by nonlinear absorption of intense laser pulses typically proceeds by localized plasma generation, which provides the pressure and temperature gradients to drive both mass motion and thermal transport. This is typically assumed to be the case for femtosecond filaments in gases, where depletion of the laser pulse energy due to absorption limits their ultimately achievable length [1] and where the thermal energy deposited in the gas can result in sound wave generation [2][3][4][5][6][7][8][9] followed by a gas density depression or 'hole' that can persist on millisecond timescales [5][6][7]. Recently it was shown that this density hole can affect filamentation at kilohertz repetition rates by acting as a negative lens [5] and can steer filaments [6].…”

“…It may even play an important role in filament-triggered electrical discharges [3,4]. New applications such as high average power laser beam guiding and remote generation of lensing structures in the atmosphere [7] can be enabled by control of energy deposition in gases by femtosecond laser pulses.…”

“…Our results make possible the fine quantum control of gas density profiles using non-ionizing laser pulses. Such profile modification, at both near and remote locations, has a range of exciting applications including the refractive index control of high power optical pulse propagation in air [5][6][7].…”

Direct imaging of the acoustic waves generated by femtosecond filaments in air

“…Gas dynamics after deposition of energy by an ultrashort optical pulse has been discussed previously [5][6][7]9,10]; we briefly review the subject here. A weakly ionized plasma created through field ionization of molecules recombines over a timescale of ~10 ns and repartitions its energy into the translational and rotational degrees of freedom of the neutral gas [7].…”