All-optical attoclock: accessing exahertz dynamics of optical tunnelling through terahertz emission

The debate regarding attosecond dynamics of optical tunneling has so far been focused on time delays associated with electron motion through the potential barrier created by intense ionizing laser fields and the atomic core. Compelling theoretical and experimental arguments have been put forward to advocate the polar opposite views, confirming or refuting the presence of tunnelling time delays. Yet, such delay, whether present or ot, is but a single quantity characterizing the tunnelling wavepacket; the underlying dynamics are richer. Here we propose to complement photo-electron detection with detecting light, focusing on the so-called Brunel adiation -- the near-instantaneous nonlinear optical response triggered by the tunnelling event. Using the combination of single-color and two-color driving fields, we determine not only the ionization delays, but also the re-shaping of the tunnelling wavepacket as it emerges from the classically forbidden region. Our work introduces a new type of attoclock for optical tunnelling, one that is based on measuring light rather than photo-electrons. All-optical detection paves the way to time-resolving multiphoton transitions across bandgaps in solids, on the attosecond time-scale

Konstitucinė valstybės tarnybos samprata ir Valstybės tarnybos tobulinimo koncepcija

Straipsnyje iš konstitucinės teisės perspektyvos nagrinėjama dabartinė Lietuvos viešojo administravimo ir valstybės tarnybos sistema, lyginami du pagrindiniai viešojo administravimo modeliai. Šiems tikslams pasiekti gana detaliai nagrinėjama Konstitucinio Teismo suformuluota konstitucinės valstybės tarnybos sampratos jurisprudencija. Vienas iš pagrindinių straipsnio tikslų – konstituciškai įvertinti 2010 metais Vyriausybės parengtą Valstybės tarnybos tobulinimo koncepciją ir įstatymų leidėjui pateikti su jos įgy­vendinimu susijusius konkrečius pasiūlymus. Lithuanian system of public administration and civil service is analysed in the article, using constitu­tional law as a tool of its legal evaluation. Some characters of two main models of public administration (the one of Max Weber and so called “New public management”) are presented and juxtaposed in or­der to understand the existing Lithuanian model. Analysis of jurisprudence of Lithuanian Constitutional Court concerning the Lithuanian civil service plays major role in assessing the constitutionality of Lithu­anian civil service improvement guidelines, developed and announced by the Lithuanian government in the beginning of 2010

Terahertz pulse generation by two-color laser fields with circular polarization

27 pages, 13 figuresInternational audienceWe study the influence of the polarization states of femtosecond two-color pulses ionizing gases on the emitted terahertz radiation. A local-current model and plane-wave evaluations justify the previously-reported impact on the THz energy yield and an (almost) linearly-polarized THz field when using circularly-polarized laser harmonics. For such pump pulses, the THz yield is independent on the relative phase between the two colors. When the pump pulses have same helicity, the increase in the THz yield is associated to longer ionization sequences and higher electron transverse momenta acquired in the driving field. Reversely, for two color pulses with opposite helicity, the dramatic loss of THz power comes from destructive interferences driven by the highly symmetric response of the photocurrents lined up on the third harmonic of the fundamental pulse. While our experiments confirm an increased THz yield for circularly polarized pumps of same helicity, surprisingly, the emitted THz radiation is not linearly-polarized. This effect is explained by means of comprehensive 3D numerical simulations highlighting the role of the spatial alignment and non-collinear propagation of the two colors

Terahertz pulse generation by multi-color laser fields with linear vs. circular polarization

International audienc