Sub-diffraction optical coherent control of ultrafast electrical currents in antenna devices on GaAs

Abstract

Femtosecond ω/2ω pulse pairs derived from a compact Er:fibre source induce coherently controlled currents in low temperature grown GaAs. They are characterized by analyzing charge accumulation at contacts closeby. We focus on the photoresponse of bowtie optical antennas integrated into such metal-semiconductor-metal structures. Antennas are designed to enhance the ω field and to confine it into the 50 nm antenna gap. The coherently controlled current is markedly enhanced by the plasmonic nanostructure. However, we find an only unpronounced dependence on the antenna length which is probably related to the large refractive index of GaAs and intricate resonance conditions for ultrabroadband excitation light.

Light-field and spin-orbit-driven currents in van der Waals materials

“…Similarly, coherent injection of spin and valley currents has been proposed for two-dimensional van der Waals materials [122,127,128]. Experimentally, the coherent control was detected either statically by measuring the net DC-current between a source and drain electrode [123,126] or dynamically by detecting the emitted THz field due to the injected current pulses in the material [129]. By contrast, time-resolved angleresolved photoemission spectroscopy (tr-ARPES) can directly image the non-equilibrium carrier distribution in kspace on femtosecond timescales [43,85,[130][131][132][133].…”

“…The forth rank tensor η αβγδ (ω) describes coherent one-and two-photon injection and includes contributions from both electrons and holes [116]. Such coherently controlled charge currents have initially been predicted and observed for bulk semiconductors, such as GaAs or Si [116,118,119,121,123], and later also for one-dimensional and two-dimensional nanoscale materials, such as carbon nanotubes, semiconductor nanowires or graphene [115,117,120,[124][125][126]. Similarly, coherent injection of spin and valley currents has been proposed for two-dimensional van der Waals materials [122,127,128].…”

Interference of stimulated electronic Raman scattering and linear absorption in coherent control

“…For a three-dimensional material, the integration over reciprocal space in Eqs. ( 2), ( 7), ( 9), (10) and (11) should read ´d3 k/8π 3 .…”

“…Coherent control (CC) involves the interference between multiple excitation pathways to acquire a handle on the final state of a quantum-mechanical process. 1 The field originates from progress in manipulating the transition rates of multiphoton molecular processes 2,3 and has since grown to encompass condensed-matter systems, including bulk and nanostructured semiconducting materials, [4][5][6][7][8][9] metal-semiconductor heterostructures, 10 and optical lattices. 11 Applied to semiconductor optics, the typical CC experiment uses light at a fundamental frequency ω and its second harmonic 2ω.…”