Electromigrated electrical optical antennas for transducing electrons and photons at the nanoscale

Abstract

Background: Electrically controlled optical metal antennas are an emerging class of nanodevices enabling a bilateral transduction between electrons and photons. At the heart of the device is a tunnel junction that may either emit light upon injection of electrons or generate an electrical current when excited by a light wave. The current study explores a technological route for producing these functional units based upon the electromigration of metal constrictions. Results: We combine multiple nanofabrication steps to realize in-plane tunneling junctions made of two gold electrodes, separated by a sub-nanometer gap acting as the feedgap of an optical antenna. We electrically characterize the transport properties of the junctions in the light of the Fowler–Nordheim representation and the Simmons model for electron tunneling. We demonstrate light emission from the feedgap upon electron injection and show examples of how this nanoscale light source can be coupled to waveguiding structures. Conclusion: Electromigrated in-plane tunneling optical antennas feature interesting properties with their unique functionality enabling interfacing electrons and photons at the atomic scale and with the same device. This technology may open new routes for device-to-device communication and for interconnecting an electronic control layer to a photonic architecture.

Effect of quantized conductivity on the anomalous photon emission radiated from atomic-size point contacts

“…In the time traces displayed in Figure 2, the amplitudes of the voltage applied during the last moment reduce the probability of G to explore the smallest integer numbers N × G 0 [35], and the last measured step is at approximately N = 4 in both cases. We have observed lower quantum numbers in the past [26,36], but typically with applied voltage before rupture below 500 mV. Figure 2 also displays the simultaneously acquired photon counts measured by the two cross-polarized APDs.…”

“…If uncontrolled, this eventually leads to a thermal runaway and a catastrophic rupture of the constriction [25]. Instead, if V b is decreased to contain the time evolution of the conductance, the electromigration process slows down, allowing us to explore the various regimes of electron transport ranging from diffusive to ballistic, and eventually tunnel when the last atomic bond breaks [26]. Quantized steps of the conductance in units of the quantum of conductance G 0 = 2e 2 /h are the signature of a ballistic transport, where e is the electron charge and h is the Planck constant [27,28].…”

Optical antennas driven by quantum tunneling: a key issues review

“…For completeness we would like to emphasize thatespecially in the high conductivity regime-alternative mechanisms such as hot-electron emission [76][77][78] and inelastic processes involving more than one electron [79][80][81][82][83] play an important role in the light emission from tunnel junctions . Recently it was also suggested that a ballistic nanoconstriction may yield a higher emission efficiency than the more widely studied tunneling gaps [84].…”

Optically and electrically driven nanoantennas

“…Under excitation with state-of-the-art lasers, ultrafast effects can be observed as well as a plethora of nonlinear characteristics [20]. Recently, also electrically driven nanoantennas have been demonstrated [21][22][23][24][25], which are an important milestone towards on-chip integration, device-todevice communication, and bilateral transduction between electrons and photons [26].…”

“…Last but not least, the electrically driven generation of photons is explored in [26] and [57]. In [26] the emission of light from electromigrated in-plane tunnel junctions is observed, where the feed-gap is shown to couple to propagating modes in waveguides with up to 30% efficiency. Making use of propagating surface plasmon polaritons (SPPs), directional light beams are created in [57].…”