Optical-field-induced current in dielectrics

Abstract

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 technology. Field-effect transistors are able to control currents at frequencies of the order of or higher than 100 gigahertz, but electric interconnects may hamper progress towards reaching the terahertz (10(12) hertz) range. All-optical injection of currents through interfering photoexcitation pathways or photoconductive switching of terahertz transients 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 breakdown, 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 1 femtosecond, 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 (10(15) hertz) domain.

Anisotropic high-harmonic generation in bulk crystals

“…Generation of high harmonics even for the circularly polarized laser fields is consistent with scattering from neighbouring sites in the crystal. These results open up the possibility of measuring field-induced charge flow 23,24,28,29 and imaging atomic orbitals in solids 30 , which we discuss in the Methods. In analogy to the conventional electron diffraction methods, solidstate HHG allows us to use electrons that are already present in the bulk matter to image the ångström-scale structure of the condensed matter.…”

Ultrafast Control of Strong-Field Electron Dynamics in Solids

“…The reversible field-induced change of absorption in the extreme ultraviolet spectral range was observed by probing the effect of an intense near-infrared field on a thin silica plate using an attosecond pulse of extreme ultra-violet radiation as a probe [9]. A subcycle turn-on of electric current in a dielectric and its manipulation with CEP-stabilized pulses was demonstrated by measuring the residual polarization induced by the laser light [10]. This last effect is most closely related to the topic of this chapter, so it is discussed in more detail in the following section.…”

“…1.2(b), an optical field that is strong enough to excite valence-band electrons of a dielectric to its conduction bands is also strong enough to significantly accelerate the created charge carriers, thus driving electric current. One of the most important findings in [10] was that such electric current can be turned on within a fraction of a half-cycle of a short intense laser pulse. This was demonstrated by irradiating a SiO 2 sample placed between two gold electrodes with CEP-stabilized laser pulses (see Fig.…”

“…However, new experiments put these phenomena in a new context, which often leads to nontrivial observations, such as the generation of nonperturbative high-order harmonics in a solid due to Bragg-like scattering at the edges of the Brillouin zone [7,8], a nearly instantaneous change in extreme-ultraviolet absorptivity and nearinfrared reflectivity of a dielectric in the presence of a laser field as strong as several volts perångström [9], or the induction of electric current in an unbiased dielectric by similarly intense laser pulses [10]. Several decades of research on strong-field phenomena in solids and mesoscopic structures provide a solid ground for developing new theoretical models adapted for new experimental conditions.…”

Correction

“…Related work with solids subjected to strong fields has also shown that the material may be reversibly changed from being a dielectric (insulator) to a semi-metal (conductor) in a femtosecond [9][10][11] .…”