Metal-dielectric-metal plasmonic resonators for active beam steering in the infrared

LIDAR and Beam Steering Tailored by Neuromorphic Metasurfaces Dipped in a Tunable Surrounding Medium

The control of amplitude, losses and deflection of light with elements of an optical array is of paramount importance for realizing dynamic beam steering for light detection and ranging applications (LIDAR). In this paper, we propose an optical beam steering device, operating at a wavelength of 1550 nm, based on high index material as molybdenum disulfide (MoS2) where the direction of the light is actively controlled by means of liquid crystal. The metasurface have been designed by a deep machine learning algorithm jointed with an optimizer in order to obtain univocal optical responses. The achieved numerical results represent a promising way for the realization of novel LIDAR for future applications with increase control and precision.

Hybrid AgNPs/MEH-PPV nanocomplexes with enhanced optical absorption and photoluminescence properties

Fluorescent semiconducting conjugated polymer nanoparticles (CPNs) are promising candidates for enhanced luminescent devices and bioimaging.

Tailoring unidirectional angular radiation through multipolar interference in a single-element subwavelength all-dielectric stair-like nanoantenna

The study of all-dielectric nanoantennas has become an emerging branch of the study of optical nanoantennas in recent years, with all-dielectric nanoantennas having an outstanding ability to tailor forward and backward unidirectional scattering arising from interference mainly between electric dipoles and magnetic dipoles induced simultaneously inside a nanoparticle. To further control their radiation properties, we demonstrate the off-normal scattering, by a silicon stair-like nanoantenna, of an incident near-infrared plane wave due to multipolar interference. The radiation angle could be tailored over a 20-degree range by tuning the geometric parameters of the nanoantenna. A multipolar model was adopted to interpret the interference among one electric dipole, two magnetic dipoles and one electric quadrupole induced inside the nanoantenna. The maximum radiation angle reached 20° at a wavelength near 1550 nm. Such a stair-like nanoantenna sets a good example for further flexible manipulation of multipolar resonances inside all-dielectric nanoparticles, which is an essential step towards practical application of all-dielectric nanoantennas in the near future.

Ultrafast beam steering using gradient Au-Ge₂Sb₂Te₅-Au plasmonic resonators

Beam steering devices have gained extensive interests in the fields of optical interconnects, communications, displays and data storages. However, the challenge lies in obtaining an ultrafast beam steering structure in the optical regime. Here, we propose phase-array-like plasmonic resonators based on metal/phase-change materials (PCMs)/metal trilayers for all-optical ultrafast beam steering in the mid-infrared (MIR) region. We numerically demonstrate an angle beam steering of 11° for transmitted wave (front lobe) and 22° for reflected wave (back lobe) by switching between the amorphous and crystalline states of the PCM (Ge₂Sb₂Te₅). A photothermal model is used to study the temporal variation of the temperature of the Ge₂Sb₂Te₅ film to show potential for switching the phase of Ge₂Sb₂Te₅ by optical heating. Generation of the beam steering in this structure exhibits a fast beam steering time of 3.6 ns under a low pump light intensity of 2.6 μW/μm₂. Our design possesses a simple geometry which can be fabricated using standard photolithography patterning and is essential for exploiting the ultrafast beam steering in various applications in the MIR regime.

Chemical control of continuous light-steering using an array of gradient Au/Bi2Se3/Au strips

Achievement of continuous light-steering in an array of gradient Au/Bi₂Se₃/Au strips by modulating the dielectric function of Bi₂Se₃.

Radiative decay engineering 7: Tamm state-coupled emission using a hybrid plasmonic-photonic structure

There is a continuing need to increase the brightness and photostability of fluorophores for use in biotechnology, medical diagnostics, and cell imaging. One approach developed during the past decade is to use metallic surfaces and nanostructures. It is now known that excited state fluorophores display interactions with surface plasmons, which can increase the radiative decay rates, modify the spatial distribution of emission, and result in directional emission. One important example is surface plasmon-coupled emission (SPCE). In this phenomenon, the fluorophores at close distances from a thin metal film, typically silver, display emission over a small range of angles into the substrate. A disadvantage of SPCE is that the emission occurs at large angles relative to the surface normal and at angles that are larger than the critical angle for the glass substrate. The large angles make it difficult to collect all of the coupled emission and have prevented the use of SPCE with high-throughput and/or array applications. In the current article, we describe a simple multilayer metal-dielectric structure that allows excitation with light that is perpendicular (normal) to the plane and provides emission within a narrow angular distribution that is normal to the plane. This structure consists of a thin silver film on top of a multilayer dielectric Bragg grating, with no nanoscale features except for the metal or dielectric layer thicknesses. Our structure is designed to support optical Tamm states, which are trapped electromagnetic modes between the metal film and the underlying Bragg grating. We used simulations with the transfer matrix method to understand the optical properties of Tamm states and localization of the modes or electric fields in the structure. Tamm states can exist with zero in-plane wavevector components and can be created without the use of a coupling prism. We show that fluorophores on top of the metal film can interact with the Tamm state under the metal film and display Tamm state-coupled emission (TSCE). In contrast to SPCE, the Tamm states can display either S or P polarization. The TSCE angle is highly sensitive to wavelength, which suggests the use of Tamm structures to provide both directional emission and wavelength dispersion. Metallic structures can modify fluorophore decay rates but also have high losses. Photonic crystals have low losses but may lack the enhanced light-induced fields near metals. The combination of plasmonic and photonic structures offers the opportunity for radiative decay engineering to design new formats for clinical testing and other fluorescence-based applications.