On the stable propagation of high-intensity ultrashort light pulses (original) (raw)
Related papers
Ultrarelativistic regime in the propagation of an ultrastrong, femtosecond laser pulse in plasmas
The interaction of a multi-Petawatt, pancake-shaped laser pulse with an unmagnetized plasma is studied analytically and numerically in the regime of fully relativistic electron jitter velocities and in the context of the laser wakefield acceleration scheme. The study is applied to the specifications available at present time, or planned for the near future, of the Ti:Sa Frascati Laser for Acceleration and Multidisciplinary Experiments (FLAME) in Frascati. A set of novel nonlinear equations is derived using a three-timescale description, with an intermediate timescale associated with the nonlinear phase of the electromagnetic wave and with the spatial bending of its wave front. They describe on an equal footing both the strong and moderate laser intensity regimes, pertinent to the core and the edges of the pulse. These have fundamentally different dispersive properties since, in the core, the electrons are almost completely expelled by a very strong ponderomotive force and the electromagnetic wave packet is imbedded in a vacuum channel and has (almost) linear properties, while at the pulse edges the laser amplitude is smaller and the wave is dispersive. The new nonlinear terms in the wave equation, introduced by the nonlinear phase, describe a smooth transition to a nondispersive electromagnetic wave at very large intensities, and the simultaneous saturation of the previously known nonlocal cubic nonlinearity, without the violation of the imposed scaling laws. The temporal evolution of the laser pulse is studied by the numerical solution of the model equations in a two-dimensional geometry, with the spot diameter presently used in the selfinjection test experiment (SITE) with FLAME. The most stable initial pulse length is found to be around 1 µm, which is several times shorter than presently available. A rapid stretching of the laser pulse in the direction of propagation is observed, followed by the development of a vacuum channel and a very large electrostatic wake potential, as well as the bending of the laser wave front.
Femtosecond Laser Pulses: Generation, Measurement and Propagation
2021
In this contribution some basic properties of femtosecond laser pulse are summarized. In sections 2.1-2.5 the generation of femtosecond laser pulses via mode locking is described in simple physical terms. In section 2.6 we deal with measurement of ultrashort laser pulses. The characterization of ultrashort pulses with respect to amplitude and phase is therefore based on optical correlation techniques that make of the short pulse itself. In section 3 we start with the linear properties of ultrashort light pulses. However, due to the large bandwidth, the linear dispersion is responsible for dramatic effects. To describe and manage such dispersion effects a mathematical description of an ultrashort laser pulse is given first before we continue with methods how to change the temporal shape via the frequency domain. The chapter ends with a paragraph of the wavelet representation of an ultrashort laser pulse.
Kilometer-range nonlinear propagation of femtosecond laser pulses
Physical Review E, 2004
Ultrashort, high-power laser pulses propagating vertically in the atmosphere have been observed over more than 20 km using an imaging 2-m astronomical telescope. This direct observation in several wavelength bands shows indications for filament formation at distances as far as 2 km in the atmosphere. Moreover, the beam divergence at 5 km altitude is smaller than expected, bearing evidence for whole-beam parallelization about the nonlinear focus. We discuss implications for white-light Lidar applications.
Asymptotic pulse shapes in filamentary propagation of intense femtosecond pulses
Laser Physics, 2009
Self-compression of intense ultrashort laser pulses inside a self-guided filament is discussed. The filament self-guiding mechanism requires a balance between diffraction, plasma self-defocusing and Kerr-type self-focusing, which gives rise to asymptotic intensity profiles on axis of the filament. The asymptotic solutions appear as the dominant pulse shaping mechanism in the leading part of the pulse, causing a pinch of the photon density close to zero delay, which substantiates as pulse compression. The simple analytical model is backed up by numerical simulations, confirming the prevalence of spatial coupling mechanisms and explaining the emerging inhomogeneous spatial structure. Numerical simulations confirm that only spatial effects alone may already give rise to filament formation. Consequently, self-compression is explained by a dynamic balance between two optical nonlinearities, giving rise to soliton-like pulse formation inside the filament.
Ultrarelativistc regime in the propagation of an ultrastrong, femtosecond laser pulse in plasmas
arXiv: Plasma Physics, 2014
SPIN-CNR, Complesso Universitario di M.S. Angelo, Napoli, Italy(Dated: July 31, 2014)The interaction of a multi-Petawatt, pancake-shaped laser pulse with an unmagnetized plasma isstudied analytically and numerically in the regime of fully relativistic electron jitter velocities andin the context of the laser wakefield acceleration scheme. The study is applied to the specificationsavailable at present time, or planned for the near future, of the Ti:Sa Frascati Laser for Accelerationand Multidisciplinary Experiments (FLAME) in Frascati. A set of novel nonlinear equations isderived using a three-timescale description, with an intermediate timescale associated with thenonlinear phase of the electromagnetic wave and with the spatial bending of its wave front. Theydescribe on an equal footing both the strong and moderate laser intensity regimes, pertinent to thecore and the edges of the pulse. These have fundamentally different dispersive properties since,in the core, the electrons are almos...
Nonlinear Effects with Ultrashort Laser Pulses
Acta Physica Polonica A, 2002
Pr oceed in gs of t he Co n f er ence \ F rom Qu an t um Op t i cs t o Ph o t on i cs" , Z ak opa n e 200 1 N on l in ear E˜e ct s w it h Ultras h ort L aser P u ls es P. W asy l c zy k Ê , W. W asil ew sk i, M. T r ipp en ba c h an d C. Radze wic z I nst i t ut e of E xp eri m ent al P h ysi cs, W arsaw Uni versi ty Hoâa 69, 00-681 Wa rsaw, Po l and Pr opagation of an int ense femtose cond laser pulse t hrough a transparent nonlin ear medium such as dielectric leads to a num ber of phenomena. I n our exp eriment we obser ved complex spatial , spectral, and temp oral structures app earing in the initi ally smo oth femtosecond laser pulse w hen the pulse p ower is comparable to or higher than the critical power for self-focusing. W e ha ve also develop ed a complete, 3-dimensi onal theoretical mo del to describ e the observed phenomena.
Simulation of femtosecond pulse propagation in air
2003
We present numerical simulations of the propagation of intense spatio-temporal fields propagating in air. Characteristic parameters of the propagation like peak intensities, plasma densities and diameters of the plasma channels are obtained. The evolution of the spectral content of the pulses is investigated and, in agreement with recent experiments, white-light supercontinuum generation is observed. We show in which areas of the pulse the supercontinuum is generated and conclude that self-phase modulation is responsible for the spectral broadening. Furthermore we investigate azimuthal instabilities of intense rotationally symmetric pulsed beams propagating in air. Although the spatial-temporal evolution of the field is strongly influenced by the onset of plasma generation, the instabilities are basically caused by the Kerr effect. We conclude that calculations assuming rotational symmetry become unrealistic due to the fast growth of azimuthal instabilities in the focal region.
Self-compression of high-intensity femtosecond laser pulses in a low-dispersion regime
Journal of Physics B: Atomic, Molecular and Optical Physics, 2007
Self-compression of high-intensity femtosecond pulses has been observed in a number of atomic and molecular gases and solid bulk material. The evolution of the femtosecond pulse parameters during the self-compression has been studied under a variety of experimental conditions. Generation of spatiotemporal solitons has been achieved by the combined action of self-compression and self-focusing.
IEEE Journal of Quantum Electronics, 1983
Recent advances in generation, amplification, compression, and frequency broadening of femtosecond optical pulses are reviewed. We describe use of colliding pulse mode locking to generate pulses of 65 fs duration and pulse compression to reduce those pulse durations to 30 fs. Amplification of femtosecond pulses to gigawatt powers and frequency broadening to obtain white light continuum pulses while retaining femtosecond pulse durations are also examined.