Wireless communication system via nanoscale plasmonic antennas

Plasmonic switches based on VO2as the phase change material

In this paper, a comprehensive review of the recent advancements in the design and development of plasmonic switches based on vanadium dioxide (VO2) is presented. Plasmonic switches are employed in applications such as integrated photonics, plasmonic logic circuits and computing networks for light routing and switching, and are based on the switching of the plasmonic properties under the effect of an external stimulus. In the last few decades, plasmonic switches have seen a significant growth because of their ultra-fast switching speed, wide spectral tunability, ultra-compact size, and low losses. In this review, first, the mechanism of the semiconductor to metal phase transition in VO2is discussed and the reasons for employing VO2over other phase change materials for plasmonic switching are described. Subsequently, an exhaustive review and comparison of the current state-of-the-art plasmonic switches based on VO2proposed in the last decade is carried out. As the phase transition in VO2can be activated by application of temperature, voltage or optical light pulses, this review paper has been categorized into thermally-activated, electrically-activated, and optically-activated plasmonic switches based on VO2operating in the visible, near-infrared, infrared and terahertz frequency regions.

Polarization-division and spatial-division shared-aperture nanopatch antenna arrays for wide-angle optical beam scanning

Chip-based optical beam scanners hold promise for future compact high-speed light detection and ranging (LIDAR) systems. Many of the demonstrated chip-based optical beam scanners are designed based on diffraction-based waveguide gratings as on-chip antennas. The waveguide grating antenna, however, only provides a typical field-of-view (FOV) of roughly 10° by tuning the input light wavelength. In this paper, polarization-division and spatial-division multiplexed nanoantenna arrays are proposed to expand the FOV of on-chip antennas. The proposed device, based on silicon-on-insulator (SOI) platform, consists of three nanoantenna groups which are densely packed and fed by a common silicon nanostrip. It is demonstrated that the combination of the optical mode-multiplexing technique and the antenna engineering allows independent controls over the interactions between multiple nanoantenna groups and the waveguide. By proper engineering of the antenna dimensions, the proposed device achieves a FOV of over 40° within a 100 nm wavelength tuning range, almost tripling that of the conventional waveguide grating antenna.

Nanoantenna enhanced terahertz interaction of biomolecules

Terahertz time-domain spectroscopy (THz-TDS) is a non-invasive, non-contact and label-free technique for biological and chemical sensing as THz-spectra are less energetic and lie in the characteristic vibration frequency regime of proteins and DNA molecules. However, THz-TDS is less sensitive for the detection of micro-organisms of size equal to or less than λ/100 (where, λ is the wavelength of the incident THz wave), and molecules in extremely low concentration solutions (like, a few femtomolar). After successful high-throughput fabrication of nanostructures, nanoantennas were found to be indispensable in enhancing the sensitivity of conventional THz-TDS. These nanostructures lead to strong THz field enhancement when in resonance with the absorption spectrum of absorptive molecules, causing significant changes in the magnitude of the transmission spectrum, therefore, enhancing the sensitivity and allowing the detection of molecules and biomaterials in extremely low concentration solutions. Herein, we review the recent developments in ultra-sensitive and selective nanogap biosensors. We have also provided an in-depth review of various high-throughput nanofabrication techniques. We also discussed the physics behind the field enhancements in the sub-skin depth as well as sub-nanometer sized nanogaps. We introduce finite-difference time-domain (FDTD) and molecular dynamics (MD) simulation tools to study THz biomolecular interactions. Finally, we provide a comprehensive account of nanoantenna enhanced sensing of viruses (like, H1N1) and biomolecules such as artificial sweeteners which are addictive and carcinogenic.

Photoluminescence Revealed Higher Order Plasmonic Resonance Modes and Their Unexpected Frequency Blue Shifts in Silver-Coated Silica Nanoparticle Antennas

Higher order plasmonic resonance modes and their frequency blue shifts in silver-coated silica nanoparticle antennas are studied. Synthesizing them with a wet chemistry method, silica (SiO2) nanoparticles were enclosed within silver shells with different thicknesses. A size-dependent Drude model was used to model the plasmonic shells and their optical losses. Two higher order plasmonic resonances were identified for each case in these simulations. The photoluminescence spectroscopy (PL) experimental results, in good agreement with their simulated values, confirmed the presence of those two higher order resonant modes and their resonance frequencies. When compared with pure metallic Ag nanoparticles, size-induced blue shifts were observed in these resonance frequencies.

Megahertz-wave-transmitting conducting polymer electrode for device-to-device integration

The ideal combination of high optical transparency and high electrical conductivity, especially at very low frequencies of less than the gigahertz (GHz) order, such as the radiofrequencies at which electronic devices operate (tens of kHz to hundreds of GHz), is fundamental incompatibility, which creates a barrier to the realization of enhanced user interfaces and ‘device-to-device integration.’ Herein, we present a design strategy for preparing a megahertz (MHz)-transparent conductor, based on a plasma frequency controlled by the electrical conductivity, with the ultimate goal of device-to-device integration through electromagnetic wave transmittance. This approach is verified experimentally using a conducting polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), the microstructure of which is manipulated by employing a solution process. The use of a transparent conducting polymer as an electrode enables the fabrication of a fully functional touch-controlled display device and magnetic resonance imaging (MRI)-compatible biomedical monitoring device, which would open up a new paradigm for transparent conductors.

The emergence of applications requiring device-to-device interactivity has to the need to develop conducting electrodes with high optical transparency at low radiofrequencies. Here, the authors demonstrate conductive polymer electrodes with high transparency in the MHz-order frequency range.

Improving the performance of optical antenna for optical phased arrays through high-contrast grating structure on SOI substrate

A novel optical antenna for optical phased arrays is proposed and simulated. A high-contrast grating structure is used to achieve extremely efficient emission. The emission efficiency is as high as 93.94% at 1.55 μm, which exceeds 50% in a range of wavelength from 1.48 μm to 1.62 μm. The antenna can achieve a perfect grating lobe suppression with background suppression of 28.4 dB when the phase difference between adjacent waveguides is 0. A 16-wire optical phased array can easily achieve a scan range of ± 22.8° × 20.2° with a beam width of 2.4° × 2.5°, by employing the optical antenna proposed.

Array of plasmonic Vivaldi antennas coupled to silicon waveguides for wireless networks through on-chip optical technology - WiNOT

Optical technology applied to on-chip wireless communication is particularly promising to overcome the performance limitations of the state-of-the-art networks on-chip. A key enabling component for such applications is the plasmonic antenna coupled to conventional silicon waveguides, which can guarantee full compatibility with standard optical circuitry. In this paper, we propose an antenna array configuration based on tilted plasmonic Vivaldi antennas coupled to a silicon waveguide. The details of the single antenna and of the array design are reported. The radiation characteristics of the array are suitable for on-chip point-to-point communication, i.e. in-plane maximum gain of 14.70 dB for an array with five antennas. The array exploits a travelling wave feeding scheme and, therefore, is compact in size (about 3.5 µm × 8.7 µm ).

All-optical wireless wavelength multiplexing and demultiplexing using resonant cavity

The potential capability of wireless wavelength multiplexing and demultiplexing can enable the next development of smaller photonic counterparts for network architectures. This paper numerically represents a new design of a wireless transmission in C-band infrared wavelengths within two identical resonant cavities between photonic chips. This system consists of an H1 rod-type two-dimensional photonic crystal (PhC) microcavity, which can be operated as both a transmitter and a receiver without interfering with the signal in each PhC waveguide. By using the point-to-point oscillatory light-field exchange between resonant cavities, two independent photonic circuits are linked with each other. The obtained results show that the multi-resonance wavelengths in one chip can be transferred to another chip located far away by ten times the highest resonance wavelength. Such a device can be useful for integrated optical circuit interconnect and small-scale sensors between photonic chips.

Unidirectional excitation of plasmonic waves via a multilayered metal-dielectric-metal Huygens' nanoantenna

Huygens' nanoantennas maintain orthogonal electric and magnetic dipole resonances satisfying the Kerker condition and can generate directional radiation in both the near-field and far-field regimes. Here we study a multilayered metal-dielectric-metal (MDM) Huygens' type nanoantenna which is capable of launching surface plasmon polaritons (SPPs) unidirectionally when excited by a dipole source. We show that the radiative decay rates of the dipole source are strongly enhanced by the antenna, and the generated SPP waves propagate in opposite directions at two different wavelengths. The directionality of the excited SPPs can be switched by changing the geometry and the material composition. We further demonstrated that the beam width of the SPP waves can be narrowed by arranging the MDM antennas in a chain.

Optical wireless link between a nanoscale antenna and a transducing rectenna

Initiated as a cable-replacement solution, short-range wireless power transfer has rapidly become ubiquitous in the development of modern high-data throughput networking in centimeter to meter accessibility range. Wireless technology is now penetrating a higher level of system integration for chip-to-chip and on-chip radiofrequency interconnects. However, standard CMOS integrated millimeter-wave antennas have typical size commensurable with the operating wavelength, and are thus an unrealistic solution for downsizing transmitters and receivers to the micrometer and nanometer scale. Herein, we demonstrate a light-in and electrical signal-out, on-chip wireless near-infrared link between a 220 nm optical antenna and a sub-nanometer rectifying antenna converting the transmitted optical energy into direct electrical current. The co-integration of subwavelength optical functional devices with electronic transduction offers a disruptive solution to interface photons and electrons at the nanoscale for on-chip wireless optical interconnects.

Integrating optical and electrical components for communication systems is challenging due to the differences of scale. The authors have developed an on-chip light-to-electrical wireless link between a nanoantenna and an optical rectifier, envisioned as a solution for future integrated wireless interconnects.

Integrated Vivaldi plasmonic antenna for wireless on-chip optical communications

In this paper we propose a novel hybrid optical plasmonic Vivaldi antenna for operation in the standard C telecommunication band for wavelengths in the 1550 nm range. The antenna is fed by a silicon waveguide and is designed to have high gain and large bandwidth. The shape of the radiation pattern, with a main lobe along the antenna axis, makes this antenna suitable for point-to-point connections for inter- or intra-chip optical communications. Direct port-to-port short links for different connection distances and in a homogeneous environment have also been simulated to verify, by comparing the results of a full-wave simulation with the Friis transmission equation, the correctness of the antenna parameters obtained via near-to-far field transformation.

Beam steering and impedance matching of plasmonic horn nanoantennas

In this paper, we study a plasmonic horn nanoantenna on a metal-backed substrate. The horn nanoantenna structure consists of a two-wire transmission line (TWTL) flared at the end. We analyze the effect of the substrate thickness on the nanoantenna's radiation pattern, and demonstrate beam steering in a broad range of elevation angles. Furthermore, we analyze the effect of the ground plane on the impedance matching between the antenna and the TWTL, and observe that the ground plane increases the back reflection into the waveguide. To reduce the reflection, we develop a transmission line model to design an impedance matching section which leads to 99.75% power transmission to the nanoantenna.