Above threshold ionization features driven by few cycles bounded inhomogeneous electric field

P. RUEDA SUESCUN; F.VIDELA; E.NEYRA; G.A. TORCHIA; M. CIAPPINA; J.A. PEREZ HERNANDEZ

Szeged

Conferencia; ATTO 2019 ? 7th International Conference on Attosecond Science and Technology; 2019

The laser-atom interaction at high intensities with ultrashort pulses(higher than 1014 W/cm2) gives rise three well knownphenomena, these are: non-sequential double ionization (NSDI), high-orderharmonic generation (HHG) and above threshold ionization (ATIs) [1-3]. Theseeffects can be explained under classical or quantum frameworks [4]. As aconsequence of these studies up to day attosecond laser physics has beenstrongly developed by taking advantage of strong field laser physics for itsgeneration and the booster impact on the metrology of attosecond pulses and alsothe monitoring phenomena in this time scale [5].This paper shows the main features of generated photoelectrons, drivenby inhomogeneous bounded strong laser fields. The term bounded apply becausethis field of strong intensity is developed in a spatially reduced zone. Thisfield arise from the collective oscillating movement of electrons in metalnanostructures, being a non-propagating one, and its function is to ionize andaccelerate the electrons. This kind of fields can beexcited by mean of fs pulsed laser illumination on bow ties gold nanostructures.Under this excitation scheme, above threshold ionization (ATIs) electronsenergies have been simulated by solving the temporal dependent Schrödingerequation (TDSE) in one dimension on Argon gas. These results were supported byclassical features obtained by integration of the Newton-Lorentz equations. Thecalculations were conducted under the single active atom (SAE) framework. Nearinfrared driven wavelengths (0.8-1.5 mm) were used for our numericalsimulations and showed that very high-energy electrons (above keV) can begenerated. For our analysis and in order to develop a real representation of thespatial dependence of the enhanced plasmonic field has been conducted by fittingthe whole generated field with two Gaussian functions. This appropriatefunction can describe faithfully the produced inhomogeneous field by thenanostructure. In this work, we have analyzed and explored this phenomenon byusing several driven wavelengths at intensities in order of 1014 W/cm2. From the obtained results, very high photoelectrons yield has beenobserved from our TSDE simulations compared to the expected homogenous fieldcase. This new characteristic can be supported considering the trajectories ofnon-recombining electrons in the HHG approach as it was described by Neyra etal. in [6].Along this paper we can also point out difference in the ATIs generationprocess comparing the results obtained under homogeneous and inhomogeneousdriven laser field. Corresponding to the latter analysis, we discuss thedifferent physical origins or corresponding physical mechanisms for the ATIsgeneration in the inhomogeneous case.References [1] L?Huillier A, Lompré L, Mainfray G and Manus C , Multiply Charged IonsFormed by Multiphoton Absorption Processes in the Continuum,  Phys. Rev. Lett. 48 1814 (1982).[2]McPherson A, GibsonG, Jara H, Johann U, Luk T S, McIntyre I A, Boyer K and Rhodes C K, Studies ofmultiphoton production of vacuum-ultraviolet radiation in the rare gases J.Opt. Soc.Am. B 4 595 (1987).[3]Paulus G G, Nicklich W, Xu H, Lambropoulos P and Walther H, Plateau inabove threshold ionization spectra  Phys.Rev. Lett. 72 2851(1994).[4]LewensteinM, Ivanov M, Balcou P, L?Huillier A and Corkum P B, Theory of high-harmonicgeneration by low-frequency laser fields, Phys. Rev. A 49 2117 (1994).[5] F.Kruass and M. I. Stockman, Attosecond metrology: from electron capture tofuture signal processing: Nature Photonics, 8, 205-213 (2014).[6]E. Neyra,F. Videla, M.F. Ciappina, J.A. Pérez-Hernández, L.Roso, M. Lewenstein, G.A. Torchia,High order harmonic generation driven by inhomogeneous plasmonics fieldsspatially bounded: influence on the cut-off law. Journal of Optics, 20,03400.(2018).