Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSubwavelength focusing of all-dielectric surface waves
129
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Micro-sized spheres can focus light into subwavelength spatial domains: a phenomena called photonic nanojet. Even though well studied in three-dimensional (3D) configurations, only a few attempts have been reported to observe similar phenomena in two-dimensional (2D) systems. This, however, is important to take advantage of photonic nanojets in integrated optical systems. Usually, surface plasmon polaritons are suggested for this purpose, but they suffer notoriously from the rather low propagation lengths due to intrinsic absorption. Here, we solve this problem and explore, theoretically, numerically, and experimentally, the use of Bloch surface waves sustained by a suitably structured all-dielectric media to enable subwavelength focusing in an integrated planar optical system. Since only a low index contrast can be achieved while relying on Bloch surface waves, we perceive a new functional element that allows a tight focusing and the observation of a photonic nanojet on top of the surface. We experimentally demonstrate a spot size of 0.66{lambda} in the effective medium. Our approach paves the way to 2D all-dielectric photonic chips for nano-particle manipulation in fluidic devices and sensing applications.
rate research
Read More
Using transmission electron microscopy (TEM) to analyse the physical-chemical surface properties of subwavlength structured silver films and finite-difference time-domain (FDTD) numerical simulations of the optical response of these structures to plane-wave excitation, we report on the origin and nature of the persistent surface waves generated by a single slit-groove motif and recently measured by far-field optical interferometry. The surface analysis shows that the silver films are free of detectable oxide or sulfide contaminants, and the numerical simulations show very good agreement with the results previously reported.
Many advances in reflective metasurfaces have been made during the last few years, implementing efficient manipulations of wavefronts, especially for plane waves. Despite numerous solutions that have been developed throughout the years, a practical method to obtain subwavelength focusing without the generation of additional undesired scattering is a challenge to this day. In this paper, we introduce and discuss lossless reflectors for focusing incident waves into a point. The solution is based on the so-called power flow-conformal surfaces that allow theoretically arbitrary shaping of reflected waves. The metamirror shape is adapted to the power flow of the sum of the incident and reflected waves, allowing a local description of the reflector surface based on the surface impedance. In particular, we present a study of two scenarios. First, we study the scenario when the field is emitted by a point source and focused at an image point (in the considered example, with the {lambda}/20 resolution). Second, we analyze a metasurface capable to focus the power of an illuminating plane wave. This work provides a feasible strategy for various applications, including detecting biological signals near the skin, sensitive power focusing for cancer therapy, and point-to-point power transfer.
Nanophotonics is an important branch of modern optics dealing with light-matter interaction at the nanoscale. Nanoparticles can exhibit enhanced light absorption under illumination by light, and they become nanoscale sources of heat that can be precisely controlled and manipulated. For metal nanoparticles, such effects have been studied in the framework of $textit{thermoplasmonics}$ which, similar to plasmonics itself, has a number of limitations. Recently emerged $textit{all-dielectric resonant nanophotonics}$ is associated with optically-induced electric and magnetic Mie resonances, and this field is developing very rapidly in the last decade. As a result, thermoplasmonics is being replaced by $textit{all-dielectric thermonanophotonics}$ with many important applications such as photothermal cancer therapy, drug and gene delivery, nanochemistry, and photothermal imaging. This review paper aims to introduce this new field of non-plasmonic nanophotonics and discuss associated thermally-induced processes at the nanoscale.
In this letter, we introduce stacked fishnet metamaterial for steering light in microwave region. We numerically demonstrate that optical Bloch oscillations and a focus of as small as one sixth of a wavelength can be achieved. The flexibility of varying geometrical parameters of the fishnet slabs provides an efficient way for tuning its local effective media parameters and opens the possibility for controlling light arbitrarily. The experiment verifies subwavelength-sized light focusing effect by scanning magnetic field at the surface of the sample directly.
Ultra-compact, densely integrated optical components manufactured on a CMOS-foundry platform are highly desirable for optical information processing and electronic-photonic co-integration. However, the large spatial extent of evanescent waves arising from nanoscale confinement, ubiquitous in silicon photonic devices, causes significant cross-talk and scattering loss. Here, we demonstrate that anisotropic all-dielectric metamaterials open a new degree of freedom in total internal reflection to shorten the decay length of evanescent waves. We experimentally show the reduction of cross-talk by greater than 30 times and the bending loss by greater than 3 times in densely integrated, ultra-compact photonic circuit blocks. Our prototype all-dielectric metamaterial-waveguide achieves a low propagation loss of approximately 3.7 dB/cm, comparable to those of silicon strip waveguides. Our approach marks a departure from interference-based confinement as in photonic crystals or slot waveguides, which utilize nanoscale field enhancement. Its ability to suppress evanescent waves without substantially increasing the propagation loss shall pave the way for all-dielectric metamaterial-based dense integration.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
