Table-top optical parametric chirped pulse amplifiers: past and present

The generation of power- and wavelength-scalable few optical cycle pulses remains one of the major challenges in modern laser physics. Over the past decade, the development of table-top optical parametric chirped pulse amplification-based systems was progressing at amazing speed, demonstrating excellent performance characteristics in terms of pulse duration, energy, peak power and repetition rate, which place them at the front line of modern ultrafast laser technology. At present, table-top optical parametric chirped pulse amplifiers comprise a unique class of ultrafast light sources, which currently amplify octave-spanning spectra and produce carrier-envelope phase-stable, few optical cycle pulses with multi-gigawatt to multi-terawatt peak powers and multi-watt average powers, with carrier wavelengths spanning a considerable range of the optical spectrum. This article gives an overview on the state of the art of table-top optical parametric chirped pulse amplifiers, addressing their relevant scientific and technological aspects, and provides a short outlook of practical applications in the growing field of ultrafast science

Energy deposition dynamics of femtosecond pulses in water

We exploit inverse Raman scattering and solvated electron absorption to perform a quantitative characterization of the energy loss and ionization dynamics in water with tightly focused near-infrared femtosecond pulses. A comparison between experimental data and numerical simulations suggests that the ionization energy of water is 8 eV, rather than the commonly used value of 6.5 eV. We also introduce an equation for the Raman gain valid for ultra-short pulses that validates our experimental procedure.Comment: 4 pages, 5 figures, submitted to Applied Physics Letter

Multiple filamentation induced by input-beam ellipticity

The standard explanation for multiple filamentation (MF) of intense laser beams has been that it is initiated by input beam noise (modulational instability). In this study we provide the first experimental evidence that MF can also be induced by input beam ellipticity. Unlike noise-induced beam breakup, the MF pattern induced by ellipticity is reproducible shot to shot. Moreover, our experiments show that ellipticity can dominate the effect of noise, thus providing the first experimental methodology for controlling the MF pattern of noisy beams. The results are explained using a theoretical model and simulations

Light Filaments Without Self Guiding

An examination of the propagation of intense 200 fs pulses in water reveals light filaments not sustained by the balance between Kerr-induced self-focusing and plasma-induced defocusing. Their appearance is interpreted as the consequence of a spontaneous reshaping of the wave packet form a gaussian into a conical wave, driven by the requirement of maximum localization, minimum losses and stationarity in the presence of non-linear absorption.Comment: Submitted to Phys. Rev. Lett. on July 7th, 200

Non-linear unbalanced Bessel beams: Stationary conical waves supported by nonlinear losses

Nonlinear losses accompanying Kerr self-focusing substantially impacts the dynamic balance of diffraction and nonlinearity, permitting the existence of localized and stationary solutions of the 2D+1 nonlinear Schrodinger equation which are stable against radial collapse. These are featured by linear conical tails that continually refill the nonlinear, central spot. An experiment shows that the discovered solution behaves as strong attractor for the self-focusing dynamics in Kerr media.Comment: 4 pages, 2 figures; experimental verification adde

Axial emission and spectral broadening in self-focusing of femtosecond Bessel beams.

We report on the experimental observations of on-axis spectral broadening arising from self-focusing of the axicon-generated femtosecond Bessel beam in water. The observed spectral broadening is interpreted by a nonlinearly phase-matched four-wave mixing process involving the intense conical pump, the axial signal and a conical idler wave

Optical time reversal from time-dependent Epsilon-Near-Zero media

Materials with a spatially uniform but temporally varying optical response have applications ranging from magnetic field-free optical isolators to fundamental studies of quantum field theories. However, these effects typically become relevant only for time-variations oscillating at optical frequencies, thus presenting a significant hurdle that severely limits the realisation of such conditions. Here we present a thin-film material with a permittivity that pulsates (uniformly in space) at optical frequencies and realises a time-reversing medium of the form originally proposed by Pendry [Science 322, 71 (2008)]. We use an optically pumped, 500 nm thick film of epsilon-near-zero (ENZ) material based on Al-doped zinc oxide (AZO). An incident probe beam is both negatively refracted and time-reversed through a reflected phase-conjugated beam. As a result of the high nonlinearity and the refractive index that is close to zero, the ENZ film leads to time reversed beams (simultaneous negative refraction and phase conjugation) with near-unit efficiency and greater-than-unit internal conversion efficiency. The ENZ platform therefore presents the time-reversal features required e.g. for efficient subwavelength imaging, all-optical isolators and fundamental quantum field theory studies

Time-resolved refractive index and absorption mapping of light-plasma filaments in water

By means of a quantitative shadowgraphic method, we performed a space-time characterization of the refractive index variation and transient absorption induced by a light-plasma filament generated by a 100 fs laser pulse in water. The formation and evolution of the plasma channel in the proximity of the nonlinear focus were observed with a 23 fs time resolution.Comment: 3 pages, 3 picture