Observation of Ultra-High-Q Resonators in the Ultrasound via Bound States in the Continuum.

The confinement of waves in open systems represents a fundamental phenomenon extensively explored across various branches of wave physics. Recently, significant attention is directed toward bound states in the continuum (BIC), a class of modes that are trapped but do not decay in an otherwise unbounded continuum. Here, the theoretical investigation and experimental demonstration of the existence of quasi-bound states in the continuum (QBIC) for ultrasonic waves are achieved by leveraging an elastic Fabry-Pérot metasurface resonator.

Fano Resonances in Metal Gratings with Sub-Wavelength Slits on High Refractive Index Silicon.

The enhancement of optical waves through perforated plates has received particular attention over the past two decades. This phenomenon can occur due to two distinct and independent mechanisms, namely, nanoscale enhanced optical transmission and micron-scale Fabry-Perot resonance. The aim of the present paper is to shed light on the coupling potential between two neighboring slots filled with two different materials with contrasting physical properties (air and silicon, for example).

Controlled Dispersion and Transmission-Absorption of Optical Energy through Scaled Metallic Plate Structures.

The dispersive feature of metals at higher frequencies has opened up a plethora of applications in plasmonics. Besides, Extraordinary Optical Transmission (EOT) reported by Ebbesen et al. in the late 90's has sparked particular interest among the scientific community through the unprecedented and singular way to steer and enhance optical energies.

Symmetrical anisotropy enables dynamic diffraction control in photonics.

Despite the steady advancements in nanofabrication made over the past decade that had prompted a plethora of intriguing applications across various fields, achieving compatibility between miniaturized photonic devices and electronic dimensions remains unachievable due to the inherent diffraction limit of photonic devices. Herein, we present an approach based on anisotropic scaling of the shapes of photonic crystals (PhCs) to overcome the diffraction limit and achieve controlled diffraction limit along the ΓX direction. Thus, we demonstrate that scaling the direction perpendicular to the wave's propagation (y-direction) by 1/2 and 1/4 significantly improves the diffraction limit by two and four orders of magnitude, respectively.

Asymmetrical Dimer Photonic Crystals Enabling Outstanding Optical Sensing Performance.

The exploration of the propensity of engineered materials to bring forward innovations predicated on their periodic nanostructured tailoring rather than the features of their individual compounds is a continuous pursuit that has propelled optical sensors to the forefront of ultra-sensitive bio-identification. Herein, a numerical analysis based on the Finite Element Method (FEM) was used to investigate and optimize the optical properties of a unidirectional asymmetric dimer photonic crystal (PhC). The proposed device has many advantages from a nanofabrication standpoint compared to conventional PhCs sensors, where integrating defects within the periodic array is imperative.

Cloaking In-Plane Elastic Waves with Swiss Rolls.

We propose a design of cylindrical cloak for coupled in-plane shear waves consisting of concentric layers of sub-wavelength resonant stress-free inclusions shaped as Swiss rolls. The scaling factor between inclusions' sizes is according to Pendry's transform. Unlike the hitherto known situations, the present geometric transform starts from a Willis medium and further assumes that displacement fields u in original medium and u ' in transformed medium remain unaffected ( u ' = u ).

Microbubble dynamics monitoring using a dual modulation method.

An experimental method for characterizing microbubbles' oscillations is presented. With a Dual Frequency ultrasound excitation method, both relative and absolute microbubble size variations can be measured. Using the same experimental setup, a simple signal processing step applied to both the amplitude and the frequency modulations yields a two-fold picture of microbubbles' dynamics.