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 05.01.2013   Карта сайта     Language По-русски По-английски
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Экология
Электротехника и обработка материалов
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Статистика публикаци


05.01.2013

Optical-field-induced current in dielectrics





Journal name:

Nature

Volume:

493,

Pages:

70–74

Date published:

(03 January 2013)

DOI:

doi:10.1038/nature11567


Received


Accepted


Published online







The time it takes to switch on and off electric current determines the rate at which signals can be processed and sampled in modern information technology1, 2, 3, 4. Field-effect transistors1, 2, 3, 5, 6 are able to control currents at frequencies of the order of or higher than 100gigahertz, but electric interconnects may hamper progress towards reaching the terahertz (1012hertz) range. All-optical injection of currents through interfering photoexcitation pathways7, 8, 9, 10 or photoconductive switching of terahertz transients11, 12, 13, 14, 15, 16 has made it possible to control electric current on a subpicosecond timescale in semiconductors. Insulators have been deemed unsuitable for both methods, because of the need for either ultraviolet light or strong fields, which induce slow damage or ultrafast breakdown17, 18, 19, 20, respectively. Here we report the feasibility of electric signal manipulation in a dielectric. A few-cycle optical waveform reversibly increases—free from breakdown—the a.c. conductivity of amorphous silicon dioxide (fused silica) by more than 18 orders of magnitude within 1femtosecond, allowing electric currents to be driven, directed and switched by the instantaneous light field. Our work opens the way to extending electronic signal processing and high-speed metrology into the petahertz (1015hertz) domain.





At a glance




left


  1. Figure 1: Optical-field-induced conductivity and current control in a dielectric.
    Optical-field-induced conductivity and current control in a dielectric.

    a, Schematic of the metal–dielectric nanojunction. b, Schematic illustration of the adiabatic energy levels of the electronic states in the valence band (VB, purple) and conduction band (CB, green) of the dielectric under the influence of a static or slowly varying strong electric field. The eigenenergies fan out as the strength of the electric field increases, resulting in avoided crossings, that is, anticrossings (inset). At low fields, the valence band states are occupied, and the conduction band states are empty. As the field strength increases, the valence band and conduction band levels cross, but the respective Wannier–Stark states are localized at distant sites, and the anticrossings are passed diabatically (that is, the conduction band states remain unpopulated) until the field approaches or exceeds ~1VÅ−1. At these field strengths, electrons may be promoted into the conduction band via Zener tunnelling, leaving the electron in the lower-energy state after the passage of the anticrossing (adiabatic transition, depicted by dashed arrow). The resultant unoccupied valence band states mediate strong single-photon resonances at visible/near-infrared angular frequencies ωNIR/VIS within the valence band (red arrow). The emergence of these resonances results in a strong transient polarizability.





  2. Figure 2: Carrier-envelope-phase control and intensity dependence of optical-field-generated electric current in SiO2.
    Carrier-envelope-phase control and intensity dependence of optical-field-generated electric current in SiO2.

    a, Plot of the -dependent component of against the change, , in the propagation length through a fused silica wedge with respect to the propagation length yielding the minimum pulse duration ( ), for polarizations perpendicular (along ; squares) and parallel (in the yz plane; circles) to the metal–dielectric interface ( VÅ−1). The data represent an average of several consecutively acquired values at a given value of . Error bars show the standard deviation, and most are smaller than the size of the symbols representing the mean values of the data. The black dashed line shows the prediction of our quantum mechanical model. For the parallel polarization, the signal is suppressed by more than an order of magnitude. The residual signal is attributed to microscopic imperfections of the macroscopically plane metal–dielectric interface, which result in locations with a non-zero perpendicular component of the field. The red dashed line (right axis) depicts the change in pulse duration (full width at half maximum intensity) as a function of , taking into account the group velocity dispersion of the visible/near-infrared pulse in the fused silica wedge. b, Plot of the maximum amplitude, , of the transferred charge against the peak amplitude, , of the applied external field polarized along : measurement (squares) and theoretical prediction (dashed line). For a given value, is determined by fitting the most pronounced oscillation of (a, squares) with a sine function. The vertical error bars account for the standard deviation of such fit. Different values of correspond to different beam sizes. Data points have been normalized accordingly. is determined by monitoring the pulse energy and the laser beam waist at the focus, and the horizontal error bars quantify random fluctuations in these parameters. is the corresponding peak intensity of the optical pulse. Data from our model have been multiplied by the effective cross-section, , of the metal–dielectric interfaces confining the active volume of the dielectric (main text).





  3. Figure 3: Subfemtosecond control of electric current with the electric field of light.
    Subfemtosecond control of electric current with the electric field of light.








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А Б В Г Д Е Ё Ж З И Й К Л М Н О П Р С Т У Ф Х Ц Ч Ш Щ Ъ Ы Ь Э Ю Я
  • Chen Wev .  honorary member of ISSC science council

  • Harton Vladislav Vadim  honorary member of ISSC science council

  • Lichtenstain Alexandr Iosif  honorary member of ISSC science council

  • Novikov Dimirtii Leonid  honorary member of ISSC science council

  • Yakushev Mikhail Vasilii  honorary member of ISSC science council

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