Cascaded self-compression of femtosecond pulses in filaments (original) (raw)
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Asymptotic pulse shapes and pulse self-compression in femtosecond filaments
Ultrafast Phenomena XVI, 2009
The balance of Kerr-type and plasma-mediated self-amplitude modulations can give rise to self-stabilizing asymptotic pulse shapes in filament propagation. These soliton-like solutions resemble experimental data and constitute the major mechanism for self-compression in femtosecond filaments.
Self-compression by femtosecond pulse filamentation: Experiments versus numerical simulations
2006
We analyze pulse self-compression in femtosecond filaments, both experimentally and numerically. We experimentally demonstrate the compression of 45 fs pulses down to a duration of 7.4 fs at millijoule pulse energies. This sixfold compression in a self-generated filament does not require any means for dispersion compensation and is highly efficient. We compare our results to numerical simulations, providing a complete propagation model that accounts for full dispersion, pressure variations, Kerr nonlinearity and plasma generation in multiphoton and tunnel regimes. The equations are numerically integrated and allow for a quantitative comparison with the experiment. Our experiments and numerical simulations reveal a characteristic spectrotemporal structure of the self-compressed pulses, consisting of a compressible blue wing and an incompressible red pedestal. We explain the underlying mechanism that leads to this structure and examine the scalability of filament self-compression with respect to pulse energy and gas pressure.
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.
Self-compression and controllable guidance of multi-millijoule femtosecond laser pulses
Optics Communications, 2008
Self-compression of multi-millijoule femtosecond laser pulses and dramatic increase of the peak intensity are found in pressurized helium and neon within a range of intensity in which the ionization modification of the material parameters by the pulse is negligible. The pulse propagation is studied by the (3+1)-dimensional nonlinear Schrodinger equation including basic lowest order optical processes-diffraction, group velocity dispersion of second order, and Kerr nonlinearity of third order. Smooth and well controllable pulse propagation dynamics is found. Constructing of compressed pulse of controllable parameters at given space target point can be achieved by a proper chose of the pulse energy and/or gas pressure.
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.
2009
This chapter concerns with the experimental observations and theoretical investigations on the propagation of intense femtosecond pulses in water and fused silica. It emphasizes spontaneous transformation of a beam into a conical (Bessel-like) wave during the filamentary propagation in media with nonlinear losses. This transformation constitutes an interpretation of the energy reservoir surrounding the high intensity central core of the filament. The adopted model is shown as being able to explain related phenomena such as the formation of multiple filaments and that of X-waves, observed experimentally in both water and fused silica.
As lasers become progressively higher in power, optical damage thresholds will become a limiting factor. Using the non-linear optics of plasma may be a way to circumvent these limits. In this paper, we report on simulations showing an enhancement to plasma wakefield self-compression of femtosecond laser pulses due to an ionization gradient at the leading edge of the pulse. By operating in a regime where wakefield generation is driven by moderately relativistic (∼10 18 W cm −2) laser pulses and proper choice of gas species, the ionization front of the pulse can lead to a frequency shift that enhances the ponderomotive force and therefore both the wakefield generation and subsequent pulse compression.
Self-compression of ultra-short laser pulses down to one optical cycle by filamentation
Journal of Modern Optics, 2006
Theoretical studies of filamentation of ultra-short near-IR laser pulses propagating in a noble gas predict near single-cycle pulses with the intensity being clamped to the field ionization threshold. Experimental results show that this method is carrier envelope offset phase preserving and provides a very simple source for generating few-cycle intense laser pulses. This suggests a very simple design for the generation of ultra-short, sub-femtosecond XUV optical pulses. XUV pulses as short as 250 attoseconds (1 as 10 À18 s) .