Nonlinear Photon-Assisted Tunneling Transport in Optical Gap Antennas

Abstract

This supplementary material provides additional details about thermal effects observed in optical rectennas, and describes the observed correlation between the photocurrent and the nonlinearity of the conductance when irradiated with increasing laser intensities. I. THERMAL EFFECTSThermal effects can drastically influence the conduction properties of a laser irradiated tunneling jonction as reviewed by S. Grafström in Ref. [1]. Among possible processes resulting from photon absorption in the metal and subsequent Joule heating, let us mention thermal expansion of the gold leads, thermally-assisted field emission and thermovoltage arising from a temperature difference of the two sides of the rectenna feedgap when the laser is irradiating either one [2]. While it is difficult to completely rule out a potential heatrelated increased conductance in the results shown in the main manuscript, heat processes are providing well defined characteristics when the sample is scanned through the focus such as a contrast reversal of the current [3]. We did observe evidence for thermal currents in a rectenna consisted of an electromigrated Ti/Au stack. The ∼5 nm thick Ti layer acts a seed layer between the glass substrate and the gold layer. In the main manuscript, a Cr layer was systematically used instead of Ti and the results discussed below were never reproduced with Cr/Au rectennas. II. OPTICAL RECTIFICATIONWithin the assumptions discussed by Mayer and co-workers in Ref. [6], the classical picture of the rectified current is given by AbstractWe introduce strongly-coupled optical gap antennas to interface optical radiation with current-

Modulatable optical radiators and metasurfaces based on quantum nanoantennas

“…This will remarkably enhance the photon-assisted tunneling effect induced in the nanojunction built by metallic nanoantennas. Possible applications of the nonlinear quantum conductivities also include a high harmonic generation, rectification, and wave mixing [39,41,[45][46][47], which can be utilized to realize various nanophotonic sources, sensors, and detectors [25][26][27], as well as energy harvesting nanodevices [25][26][27], (i.e., optical rectennas). We should also note that when a nanoantenna is loaded with nonlinear dielectrics, the resonance frequency is also shiftable due to the electro-optic effect.…”

“…Hence, these quantum conductivities may contribute relevant resistive responses, which are frequency-dependent and can be controlled by the dc bias (σ (1) ω and σ (3) ω ) or by the intensity of illuminating laser (σ (3) ω ). In (2), there are also other higher order conductivities, such as σ (3) 3ω ≡ σ (3) (3ω; ω,ω,ω) associated with the thirdharmonic generation and four-wave mixing [40,41,[45][46][47], which will be observed at high illumination intensity. The rectification and second-harmonic generation (SHG), related to the second-order conductivities σ…”

Plasmon-Assisted Resonant Electron Tunneling in a Scanning Tunneling Microscope Junction

“…4, the potential gradient in the junction at V n', is smaller than that at V n , causing the different spacing of the FER levels. The Stark effect is dominated by the applied DC bias voltage, whereas the influence of the AC near-field oscillating at optical frequencies may be negligible as estimated for a nanoscale gap [34].…”

Designing Plasmonic Eigenstates for Optical Signal Transmission in Planar Channel Devices

“…[1][2][3][4][5][6] Surface plasmon (SP) propagated in films, [7][8] waveguided in grooves [9][10][11] or stripes [12][13][14] has proven efficient in transmitting or even processing information to and from optical and optoelectronic planar devices. [15][16][17] The optoelectronic conversion has become more challenging as the size of electronic devices is reaching the nanoscale though recent advanced functionalities based upon particle chains [18][19][20] and atomic-size gaps [21][22][23][24][25][26] could allow the next level of downsizing. Notably, even at the nanoscale, the dominant approach to signal transmission consists in propagating along a selected wave vector or inside a onedimensional (1D) waveguide, but lossy in-and out-coupling usually limit the overall transfer efficiency.…”