TiN-GST-TiN all-optical reflection modulator for the 2 µm wave band reaching 85% efficiency.

In this study, we present an all-optical reflection modulator for the 2 µm communication band exploiting a nanogear-array metasurface and phase-change-material G e 2 S b 2 T e 5 (GST). The reflectance of the structure can be manipulated by altering the phase of GST by employing optical stimuli, and this paper provides details on the optical and opto-thermal modeling techniques of GST. A numerical investigation reveals that the metastructure exhibits a conspicuous changeover from ∼99% absorption to very poor interaction with the operating light depending on the switching states of the GST, ending up with 85% modulation depth and only 0.58 dB insertion loss. Due to noticeable differences in optical responses, we can demonstrate a high extinction ratio of 28 dB and a commendable figure of merit of 49, so far the best modulation performance in this wavelength window, to our knowledge. In addition, real-time tracking of reflectance during phase transition manifests high-speed switching expending low energy per cycle, of the order of sub-nJ. Hence, given its overall performance, the device will be a paradigm for optical modulators for upcoming 2 µm communication technology.

Structurally tunable gear-shaped plasmonic sensor.

We present a gear-shaped plasmonic nano-structure with structural tunability and high RI sensitivity. New tunable geometric parameters of the gear-tooth give further flexibility for design. By using FDTD method, the reflection spectrum of the structure is theoretically analyzed with analyte RI in the range of 1.0 to 1.44. The best achieved sensitivity is- 1044 nm/RIU for our proposed structure. The resonance wavelength of the structure is independent of the polarization angle for large number of teeth. The structure can be used to design tunable sensors for biomedical and chemical applications.

Hybrid plasmonic waveguides formed by metal coating of dielectric ridges.

Bound hybrid plasmon-polariton modes supported by waveguides, which are formed by gold coating of ridges etched into a silica substrate, are analyzed using numerical simulations and investigated experimentally using near-field microscopy at telecom wavelengths (1425-1625 nm). Drastic modifications of the fundamental mode profile along with changes in the mode confinement and propagation loss are found when varying the ridge height. The main mode characteristics (effective mode index, propagation length, and mode profile) are determined from the experimental amplitude- and phase-resolved near-field images and compared with the simulations. The possibility of strongly influencing the mode properties along with subwavelength confinement found simultaneously with relatively long propagation can further be exploited in mode shaping and sensing applications.

Sb2S3/AlGaAs-based reconfigurable metasurface for dynamic polarization and directionality control of quantum emitter emission.

In this article, we report, to the best of our knowledge, for the first time, phase change material (PCM)-based reconfigurable metasurfaces for tailoring different degrees of freedom (DoF) of the quantum emitter (QE) emission, namely polarization and directionality, two key controlling factors in applications such as quantum computing, communication, and chiral optics. We have used a hybrid plasmon-QE coupled bullseye grating system utilizing the unexplored concept of composite nano-antennas in quantum photonics as the basic building block of the structures. Carefully engineered azimuthal width profile of the Sb2S3/AlGaAs composite ridge and selectively controlled transition of PCM (Sb2S3) states provide dynamic control over the amplitude and phase of the scattered radiation. Based on this methodology, we have designed five different metasurfaces for on-demand switching of target DoFs of QE emission, ensuring high collection efficiency due to the near-field coupling scheme. The first two metasurfaces switch the majority of the outgoing radiation from radially polarized to circularly polarized, whereas the next two switch the direction of circularly polarized outgoing radiation by a maximum of 9.23° while maintaining the spin state (or polarization chirality) in the simulation environment. The third metasurface category is capable of on-demand generation and separation of opposite spin states of outgoing radiation by 11.48° utilizing the selectively controlled phase transition of Sb2S3. Such reconfigurable multi-dimensional manipulation of QE radiation has not been investigated previously. This work proves the vast potential of active metasurfaces to modify the DoFs of QE emission, paving the way for high-dimensional quantum sources for high-speed quantum communication, higher dimensional quantum processing, and switchable chiral optics.

Biomimicry in nanotechnology: a comprehensive review.

Biomimicry has been utilized in many branches of science and engineering to develop devices for enhanced and better performance. The application of nanotechnology has made life easier in modern times. It has offered a way to manipulate matter and systems at the atomic level. As a result, the miniaturization of numerous devices has been possible. Of late, the integration of biomimicry with nanotechnology has shown promising results in the fields of medicine, robotics, sensors, photonics, etc. Biomimicry in nanotechnology has provided eco-friendly and green solutions to the energy problem and in textiles. This is a new research area that needs to be explored more thoroughly. This review illustrates the progress and innovations made in the field of nanotechnology with the integration of biomimicry.

A review on plasmonic and metamaterial based biosensing platforms for virus detection.

Due to changes in our climate and constant loss of habitat for animals, new pathogens for humans are constantly erupting. SARS-CoV-2 virus, become so infectious and deadly that they put new challenge to the whole technological advancement of healthcare. Within this very decade, several other deadly virus outbreaks were witnessed by humans such as Zika virus, Ebola virus, MERS-coronavirus etc. and there might be even more infectious and deadlier diseases in the horizon. Though conventional techniques have succeeded in detecting these viruses to some extent, these techniques are time-consuming, costly, and require trained human-resources. Plasmonic metamaterial based biosensors might pave the way to low-cost rapid virus detection. So this review discusses in details, the latest development in plasmonics and metamaterial based biosensors for virus, viral particles and antigen detection and the future direction of research in this field.

Modulating phase by metasurfaces with gated ultra-thin TiN films.

Active control over the flow of light is highly desirable because of its applicability to information processing, telecommunication, and spectroscopic imaging. In this paper, by employing the tunability of carrier density in a 1 nm titanium nitride (TiN) film, we numerically demonstrate deep phase modulation (PM) in an electrically tunable gold strip/TiN film hybrid metasurface. A 337° PM is achieved at 1.550 µm with a 3% carrier density change in the TiN film. We also demonstrate that a continuous 180° PM can be realized at 1.537 µm by applying a realistic experiment-based gate voltage bias and continuously changing the carrier density in the TiN film. The proposed design of active metasurfaces capable of deep PM near the wavelength of 1.550 µm has considerable potential in active beam steering, dynamic hologram generation, and flat photonic devices with reconfigurable functionalities.

Controlling the Polarization State of Light with Plasmonic Metal Oxide Metasurface.

Conventional plasmonic materials, namely, noble metals, hamper the realization of practical plasmonic devices due to their intrinsic limitations, such as lack of capabilities to tune in real-time their optical properties, failure to assimilate with CMOS standards, and severe degradation at increased temperatures. Transparent conducting oxide (TCO) is a promising alternative plasmonic material throughout the near- and mid-infrared wavelengths. In addition to compatibility with established silicon-based fabrication procedures, TCOs provide great flexibility in the design and optimization of plasmonic devices because their intrinsic optical properties can be tailored and dynamically tuned. In this work, we experimentally demonstrate metal oxide metasurfaces operating as quarter-waveplates (QWPs) over a broad near-infrared (NIR) range from 1.75 to 2.5 µm. We employ zinc oxide highly doped with gallium (Ga:ZnO) as the plasmonic constituent material of the metasurfaces and fabricate arrays of orthogonal nanorod pairs. Our Ga:ZnO metasurfaces provide a high degree of circular polarization across a broad range of two distinct optical bands in the NIR. Flexible broad-band tunability of the QWP metasurfaces is achieved by the significant shifts of their optical bands and without any degradation in their performance after a post-annealing process up to 450 °C.