Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto-and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds (1 attosecond=1 as=10 −18 s), which is comparable with the optical field. For comparison, the revolution of an electron on a 1s orbital of a hydrogen atom is ∼ 152 as. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this report on progress we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spatially inhomogeneous laser induced fields at a nanometer scale modify the laser-driven electron dynamics. Consequently, this has important impact on pivotal processes such as above-threshold ionization and high-order harmonic generation. The deep understanding of the coupled dynamics between these spatially inhomogeneous fields and matter configures a promising way to new avenues of research and applications. Thanks to the maturity that attosecond physics has reached, together with the tremendous advance in material engineering and manipulation techniques, the age of atto-nano physics has begun, but it is in the initial stage. We present thus some of the open questions, challenges and prospects for experimental confirmation of theoretical predictions, as well as experiments aimed at characterizing the induced fields and the unique electron dynamics initiated by them with high temporal and spatial resolution.

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Light beams carrying orbital angular momentum, such as Laguerre-Gaussian beams, give rise to the violation of the standard dipolar selection rules during the interaction with matter yielding, in general, an exchange of angular momentum larger thanh per absorbed photon. By means of ab initio 3D numerical simulations, we investigate in detail the interaction of a hydrogen atom with intense Gaussian and Laguerre-Gaussian light pulses. We analyze the dependence of the angular momentum exchange with the polarization, the orbital angular momentum, and the carrier-envelope phase of light, as well as with the relative position between the atom and the light vortex. In addition, a quantum-trajectory approach based on the de Broglie-Bohm formulation of quantum mechanics is used to gain physical insight into the absorption of angular momentum by the hydrogen atom.

We report continuous wave 1.06 m laser operation in an optical waveguide fabricated in a Nd:YAG ceramic by femtosecond laser writing. Single mode and stable laser oscillation have been achieved by using the natural Fresnel reflection for optical feedback. Output laser power in excess of 80 mW and a laser slope efficiency of 60% have been demonstrated. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2890073͔Femtosecond direct laser writing ͑DLW͒ of transparent materials is attracting much attention because of the unique possibility of three-dimensionally modifying, at the micrometric and submicrometric scale, the optical properties of the irradiated media. This technique has been already proved to be a powerful and flexible tool for the fabrication of a great variety of optoelectronic components such as photonic crystals, diffraction gratings, and optical memories.1-3 When femtosecond pulses are focused inside a dielectric material, a permanent change in the refractive index is produced, in such a way that optical waveguides could be generated. This possibility has been already demonstrated in a great variety of glasses and crystals. [4][5][6] The further use of the DLW technique for the fabrication of low-loss channel waveguides in laser materials could be highly advantageous with respect to other fabrication approaches, and could also lead to technology breakthroughs in the development of threedimensionally integrated optical circuits.Among the different solid state laser media, neodymium doped yttrium aluminum garnet ͑YAG͒ transparent ceramics are nowadays attracting a great interest because of its advantages over the traditionally used Nd:YAG crystals. These advantages are the lower manufacturing costs, the possibility of high neodymium contents without any decrease in the optical quality of the gain medium, and also the possibility of direct composite fabrication.7 As a matter of fact, the laser performance of Nd:YAG ceramics has been found to be equal or even superior to that corresponding to Nd:YAG crystals. 8 Recently, authors reported on the fabrication of near surface channel waveguides in Nd:YAG ceramics.9 Nevertheless, up to date no attempt has been made, to the best of our knowledge, for the fabrication of buried channel waveguides in Nd:YAG ceramics by femtosecond DLW. The possible application of such waveguides as reliable and integrated laser sources is, therefore, still unexplored.In this letter, we report on the fabrication of buried channel waveguide lasers in Nd:YAG ceramics by using a two line confinement approach. Light confinement has been achieved between two parallel tracks due to filamentation of the femtosecond laser pulses. The possible influence of the waveguide fabrication process on the spectroscopic properties of the neodymium ions has been investigated by timeresolved confocal microscopy. We have also demonstrated highly efficient and stable laser oscillation based on the femtosecond written waveguide.The Nd:YAG ceramic sample used in this work was provided by Baikowski Ltd....

We present numerical simulations of high-order harmonic generation in helium using a temporally synthesized and spatially nonhomogeneous strong laser field. The combination of temporal and spatial laser field synthesis results in a dramatic cutoff extension far beyond the usual semiclassical limit. Our predictions are based on the convergence of three complementary approaches: resolution of the three dimensional time dependent Schrödinger equation, time-frequency analysis of the resulting dipole moment, and classical trajectory extraction. A laser field synthesized both spatially and temporally has been proven capable of generating coherent extreme ultraviolet photons beyond the carbon K edge, an energy region of high interest as it can be used to initiate inner-shell dynamics and study time-resolved intramolecular attosecond spectroscopy.

The physics of laser-mater interactions beyond the perturbative limit configures the field of extreme non-linear optics. Although most experiments have been done in the near infrared ( lambda

Intense laser ionization expands Einstein's photoelectric effect rules giving a wealth of phenomena widely studied over the last decades. In all cases, so far, photons were assumed to carry one unit of angular momentum. However it is now clear that photons can possess extra angular momentum, the orbital angular momentum (OAM), related to their spatial profile. We show a complete description of photoionization by OAM photons, including new selection rules involving more than one unit of angular momentum. We explore theoretically the interaction of a single electron atom located at the center of an intense ultraviolet beam bearing OAM, envisaging new scenarios for quantum optics.

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