Superconducting analogue of optical plasmonic waveguides

We demonstrate a direct analogy between electromagnetic properties of superconductors at frequencies up to 6 THz (superconducting gap) and plasmonic metals in the optical part of the spectrum. We also identify the existence of a surface bound mode in superconducting waveguide structures, "superconducting plasmon", that closely connected to surface plasmon polaritons in the noble metals. This is a peculiar low-frequency, low-loss mode that can be guided for tens of centimetres and confined on the scale of just few tens of nanometres, demonstrating an incredible application potential

Flux Exclusion Superconducting Quantum Metamaterial: Towards Quantum-level Switching

Nonlinear and switchable metamaterials achieved by artificial structuring on the subwavelength scale have become a central topic in photonics research. Switching with only a few quanta of excitation per metamolecule, metamaterial's elementary building block, is the ultimate goal, achieving which will open new opportunities for energy efficient signal handling and quantum information processing. Recently, arrays of Josephson junction devices have been proposed as a possible solution. However, they require extremely high levels of nanofabrication. Here we introduce a new quantum superconducting metamaterial which exploits the magnetic flux quantization for switching. It does not contain Josephson junctions, making it simple to fabricate and scale into large arrays. The metamaterial was manufactured from a high-temperature superconductor and characterized in the low intensity regime, providing the first observation of the quantum phenomenon of flux exclusion affecting the far-field electromagnetic properties of the metamaterial

Generating Tesla magnetic pulses in plasmonic nanostructures

Bimetallic plasmonic ring resonators illuminated by femtosecond laser pulses generate transient subpicosecond thermoelectric currents and nanoconfined Tesla-scale magnetic fields

Resonant Thermoelectric Nanophotonics

Photodetectors are typically based either on photocurrent generation from electron–hole pairs in semiconductor structures or on bolometry for wavelengths that are below bandgap absorption. In both cases, resonant plasmonic and nanophotonic structures have been successfully used to enhance performance. Here, we show subwavelength thermoelectric nanostructures designed for resonant spectrally selective absorption, which creates large localized temperature gradients even with unfocused, spatially uniform illumination to generate a thermoelectric voltage. We show that such structures are tunable and are capable of wavelength-specific detection, with an input power responsivity of up to 38 V W^(–1), referenced to incident illumination, and bandwidth of nearly 3 kHz. This is obtained by combining resonant absorption and thermoelectric junctions within a single suspended membrane nanostructure, yielding a bandgap-independent photodetection mechanism. We report results for both bismuth telluride/antimony telluride and chromel/alumel structures as examples of a potentially broader class of resonant nanophotonic thermoelectric materials for optoelectronic applications such as non-bandgap-limited hyperspectral and broadband photodetectors

A Single-Photon Imager Based on Microwave Plasmonic Superconducting Nanowire

Detecting spatial and temporal information of individual photons by using single-photon-detector (SPD) arrays is critical to applications in spectroscopy, communication, biological imaging, astronomical observation, and quantum-information processing. Among the current SPDs1,detectors based on superconducting nanowires have outstanding performance2, but are limited in their ability to be integrated into large scale arrays due to the engineering difficulty of high-bandwidth cryogenic electronic readout3-8. Here, we address this problem by demonstrating a scalable single-photon imager using a single continuous photon-sensitive superconducting nanowire microwave-plasmon transmission line. By appropriately designing the nanowire's local electromagnetic environment so that the nanowire guides microwave plasmons, the propagating voltages signals generated by a photon-detection event were slowed down to ~ 2% of the speed of light. As a result, the time difference between arrivals of the signals at the two ends of the nanowire naturally encoded the position and time of absorption of the photon. Thus, with only two readout lines, we demonstrated that a 19.7-mm-long nanowire meandered across an area of 286 {\mu}m * 193 {\mu}m was capable of resolving ~590 effective pixels while simultaneously recording the arrival times of photons with a temporal resolution of 50 ps. The nanowire imager presents a scalable approach to realizing high-resolution photon imaging in time and space

Novel approaches in manipulating, guiding, and generating THz and sub-THz fields

This thesis serves to address the main challenges of the terahertz technology, providing new efficient ways of actively manipulating, guiding, and generating THz and sub-THz fields. This is accomplished by taking a truly interdisciplinary approach and exploiting the physics of superconductors, and the electrodynamics of metamaterial and plasmonic structures. Metamaterial arrays made of superconducting films are suggested for manipulating the THz radiations, while superconducting plasmonic waveguides are considered for achieving efficient propagation of THz waves. In addition, metamaterial arrays composed of bimetallic rings that exhibit both plasmonic and thermoelectric properties are investigated as a possible new source of THz radiation and strong magnetic fields.I have demonstrated experimentally, for the first time, that high- and low-critical temperature superconducting metamaterials are able to show sub-radiant resonances of Fano type that can be controlled with temperature. Such metamaterial resonances show vanishing radiation losses, while superconductors have very low Ohmic losses. Thus, these structures offer an efficient way to actively manipulate sub-THz (and THz) fields.I have reported on the first experimental realisation of the extraordinary transmission effect in periodically perforated superconducting films. I have shown that the level of transmission of sub-THz waves through these structures could be controlled with temperature near the superconducting transition point. The latter enabled to identify the role of the plasmonic excitations in the mechanism of extraordinary transmission. I have shown that superconductors below their gap-frequency (several THz for high-temperature superconductors) are similar in behaviour to plasmonic metals at optical frequencies. Geometries of superconducting structures have been identified that support almost dispersionless propagation of plasmonic-like modes with frequencies up to several THz, exhibiting both extreme localisation and very low propagation losses. Finally, I have theoretically demonstrated that metamaterial arrays composed of bimetallic gold-nickel nanorings, when illuminated by ultrafast optical pulses, support transient thermoelectric currents that lead to the generation of magnetic pulses of subpicosecond duration, nanoscale localisation and peak amplitudes of the order of one Tesla. These results could facilitate the study of ultrafast nanoscale magnetic phenomena and have potential use in such applications as material characterisation and magnetic recording

Superconducting plasmonics and metamaterials: from extraordinary transmission to Fano resonances

By varying temperature superconductors can be converted from lossy to ideal metals, permitting the control of both extraordinary transmission in arrays of subwavelength holes, and quality factors of Fano resonances in superconducting metamaterial films