We introduce an approach to implement full coherent control on nanometer length scales. It is based on spatio-temporal modulation of the surface plasmon polariton (SPP) fields at the thick edge of a nanowedge. The SPP wavepackets propagating toward the sharp edge of this nanowedge are compressed and adiabatically concentrated at a nanofocus, forming an ultrashort pulse of local fields. The one-dimensional spatial profile and temporal waveform of this pulse are completely coherently controlled.PACS numbers: 71.45.Gm, 42.65.Re, 73.20.Mf Two novel areas of optics have recently attracted a great deal of attention: nanooptics and ultrafast optics. One of the most rapidly developing directions in ultrafast optics is quantum control, in which coherent superpositions of quantum states are created by excitation radiation to control the quantum dynamics and outcomes 1,2,3,4 . Of special interest are coherently controlled ultrafast phenomena on the nanoscale where the phase of the excitation waveform along with its polarization provides a functional degree of freedom to control nanoscale distribution of energy 5,6,7,8,9,10 . Spatiotemporal pulse shaping permits one to generate dynamically predefined waveforms modulated both in frequency and in space to focus ultrafast pulses in the required microscopic spatial and femtosecond temporal domains 11,12 .In this Letter, we propose and theoretically develop a method of full coherent control on the nanoscale where a spatiotemporally modulated pulse is launched in a graded nanostructured system. Its propagation and adiabatic concentration provide a possibility to focus the optical energy in nanoscale spatial and femtosecond temporal regions. The idea of adiabatic concentration 13,14 (see also Ref. 15) is based on adiabatic following by the propagating surface plasmon-polariton (SPP) wave of a plasmonic waveguide, where the phase and group velocities decrease toward a limit at which the propagating SPP wave is adiabatically transformed into a standing surface plasmon (SP) mode. This effect has been further developed theoretically 16,17 and observed experimentally. 18 To illustrate the idea of this full coherent control, consider first the adiabatic concentration of a plane SPP wave propagating along a nanowedge of silver 19 , as shown in Fig. 1(a); the theory is based on the Wentzel-KramersBrillouin (WKB) or quasiclassical approximation, also called the eikonal approximation in optics 20 as suggested in Refs. 13,14. The propagation velocity of the SPP along such a nanowedge is asymptotically proportional to its thickness. Thus when a SPP approaches the sharp edge, it slows down and asymptotically (in the ideal limit of zero thickness at the apex) stops while the local fields are increased and nano-concentrated. Now consider a family of SPP rays (WKB trajectories) propagating from the thick side of a nanowedge, as shown in Fig. 1(b). One possibility to launch such SPPs is to have nanoscale inhomogeneities (nanoparticles or nanoholes) at the thick edge of the wedge. Each of the o...

We introduce an effect of metallization of dielectric nanofilms by strong, adiabatically varying electric fields. The metallization causes optical properties of a dielectric film to become similar to those of a plasmonic metal (strong absorption and negative permittivity at low optical frequencies). The is a quantum effect, which is exponentially size-dependent, occurring at fields on the order of 0.1 V/Å and pulse durations ranging from ∼ 1 fs to ∼ 10 ns for film thickness 3 − 10 nm. PACS numbers: 73.20.Mf 77.22.Jp 42.65.Re, 72.20.Ht Effects of strong electric fields on electron states in crystals have attracted a great deal of attention over many decades going back to Zener who predicted breakdown due to interband tunneling 1 . In insulators this requires electric fields on the order of atomic fields E ∼ 1 − 10 V/Å. Interest to strong-field condensed matter physics has recently greatly increased due to the availability of such strong electric fields in laser pulses of intensities I ∼ 10 13 − 10 15 W/cm 2 . Ultrashort laser pulses with a few optical oscillations2,3 open up a possibility to study ultrastrong field phenomena in solids during periods of time too short for the lattice ions to move significantly. Recent ab initio calculations 4 have reproduced the Zener breakdown in insulators induced by a laser pulse of intensity ∼ 10 15 W/cm 2 . Other strongfield phenomena that can be observable in crystals at a comparable field strength are the appearance of localized electron states, Wannier-Stark ladder in the energy spectrum 5,6 , and Bloch oscillations. 7 At orders of magnitude lower intensities, low-frequency optical fields cause a reduction of the band gap in semiconductors and insulators (Franz-Keldysh effect, FKE) 8,9 . The quantum confined FKE takes place in semiconductor quantum wells and is determined not by the field but by the total potential drop.10 It requires typical fields E ∼ 10 −3 V/Å.In this Letter we introduce an effect of metallization in insulator nanofilms, which is predicted to occur in applied electric fields E ∼ 0.1 V/Å. It is based on adiabatic electron transfer in space across the nanofilm. The minimum duration of the field pulse required for the adiabaticity exponentially depends on the crystal thickness varying from ∼ 1 fs for a 3 nm film to ∼ 10 ns for a 10 nm film thickness. This metallization effect manifests itself by a dramatic change in the optical properties of the system, which start to remind those of metals. In particular, plasmonic phenomena emerge.To demonstrate the metallization effect, we need to solve the one-electron Schrödinger equation for a periodic potential plus a uniform electric field very accurately. We will employ the widely used Kronig-Penney model for electrons in a film confined in the x direction by an infinite potential well. The corresponding potential energy (neglecting the electron-electron interaction) iswhere, and a is the lattice constant. Crystal thickness L is determined by the number of the lattice periods N in the x direction, L = N a. Thou...

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Here, for the first time we predict a giant surface-plasmon-induced drag-effect rectification (SPIDER), which exists under conditions of the extreme nanoplasmonic confinement. In nanowires, this giant SPIDER generates rectified THz potential differences up to 10 V and extremely strong electric fields up to approximately 10(5)-10(6) V/cm. The giant SPIDER is an ultrafast effect whose bandwidth for nanometric wires is approximately 20 THz. It opens up a new field of ultraintense THz nanooptics with wide potential applications in nanotechnology and nanoscience, including microelectronics, nanoplasmonics, and biomedicine.

We predict a dynamic metallization effect where an ultrafast (single-cycle) optical pulse with a ≲1 V/Å field causes plasmonic metal-like behavior of a dielectric film with a few-nm thickness. This manifests itself in plasmonic oscillations of polarization and a significant population of the conduction band evolving on a ~1 fs time scale. These phenomena are due to a combination of both adiabatic (reversible) and diabatic (for practical purposes irreversible) pathways.