Tamm modes, strongly confined between a metal and a distributed Bragg reflector (DBR), offer the advantage of being accessible with conventional excitation sources, without requiring coupling elements such as prisms. Here, we experimentally observe higher-order Tamm modes in such structures by inserting a cavity between the metal and the Bragg reflector. These modes exhibit stronger energy localization and higher quality factors than conventional Tamm modes, making them attractive candidates for future optical sensing applications. To explore their potential for refractive index sensing while maintaining the excitation conditions of higher-order Tamm modes, we numerically investigate a nanostructuring of both the gold layer and the cavity. This approach preserves the high reflectivity of the gold layer, ensuring the excitation of Tamm modes, while enabling access of the analyte to the confined field region, thereby providing a promising proof-of-concept for future liquid sensing applications.

This paper presents an analytical study of bound states in the continuum (BICs) in a photonic step-ladder waveguide structure. We demonstrate that BICs can arise in a cavity formed by one vertical and two horizontal waveguides inserted between two semi-infinite leads. Using the Green’s function method, we derive exact analytical expressions for the system’s eigenmodes, transmission, reflection, and the conditions required for BIC formation under both Neumann and Dirichlet boundary conditions. We show that when the horizontal waveguide lengths are commensurate, BICs are generated independently of the vertical guide length, allowing resonance control through geometric design. Depending on the vertical guide length, the system operates in either weak or strong coupling regimes, producing Friedrich-Wintgen BICs (FW-BICs). Breaking the symmetry of the structure leads to electromagnetically induced transparency (EIT) or reflection (EIR) resonances with sharp transmission peaks and high quality factors, making the proposed design promising for highly sensitive photonic sensing applications.

Bound states in the continuum (BICs) has emerged as a significant research focus in electronics due to its exceptionally high quality factor (Q-factor). BICs (known also as trapped modes) are not observable from the spectrum due to their non-radiative property. However, they can exist only under a specific choice of the materials or geometrical parameters of the structure. In this paper a BIC eigenfunction is defined to be strictly localized within a subspace of the cavity structure under study and has no leakage behaviour. Its eigen wavelength can be within state continua. BICs and long-lived resonances (LLR) have become a unique way to produce the extreme confinement of electronic waves. We present a theoretical and numerical demonstration of semi-infinite bound states in the continuum (SIBICs) and LLR in a two ring-like electronic micro-cavity coupled to two electronic rib/ridge wave-guides, together with their existence conditions. This structure is composed of two tangent closed loops of lengths $$L_1$$ and $$L_2$$, and two semi-infinite leads. SIBICs are localized in a semi-infinite subspace domain induced transmission zeros. Other induce transmission ones in the middle of long-lived resonances. The BICs correspond to localized resonances of infinite lifetime inside the cavity, without any leakage into the surrounding leads. When BICs exist within state continua, they induce Fano resonances exhibiting sharp peaks in the transmittance spectra and in the variation of the density of states (VADOS) for specific values of the geometrical parameters $$L_1$$ and $$L_2$$. We demonstrate that the condition for the existence of the BICs is to make the lengths $$L_1$$ and $$L_2$$ commensurate with each other. This enables to control the resonances by engineering these lengths. Finally, such a two-tangent loops cavity can be designed to realize near-perfect absorption for some frequencies. The results obtained take due account of the state number conservation between the final system and the reference one. This conservation rule enables to find all the states of the final system and among them the BIC ones. The analytical results are obtained by means of the Green’s function technique. The cavity structure and the LLR presented in this work may have potential applications due to their high sensitivities to weak perturbations, in particular in sensing and wave filtering.

We theoretically study a random arrangement of cylindrical gold nanoparticles (NPs) deposited on a dielectric/gold substrate as a potential plasmonic physically unclonable function (PUF). We use the coupled dipole approximation (CDA) method in order to reduce the computation time and memory demand. Each NP is modeled as a single electric dipole through the polarizability tensor of a spheroidal-shaped NP, while the interparticle coupling is described by Green’s tensors. The concept of plasmonic PUF considered here consists of transforming the electric field maps obtained by the CDA into 2D-binary matrices using a key generation algorithm. A PUF must satisfy different criteria to be efficient, including uniqueness that is evaluated by the distributions of Hamming inter-distances. In this work, we propose to evaluate the uniqueness property of different PUFs characterized by substrates whose dielectric layer thickness is variable. We also test the ability to generate unique keys when the challenges to which our PUF concept is subjected change, namely, the wavelength, angle, and plane of incidence.

In this work, we propose a sensor based on Tamm plasmonic resonance; the structure is composed of gold nanoribbons deposited on a Distributed Bragg Reflector (DBR) (SiO 2 /Si 3 N 4 ) 6 .We have enhanced the sensitivity of our sensor from 40 nm/RIU to 200 nm/RIU for a refractive index change of 1% by replacing the last layer of Si 3 N 4 in contact with gold with porous Si 3 N 4 with a porosity of p = 40%.

In this article, we introduce a gas sensor concept consisting of a nanostructured gold grating coupled with a distributed Bragg reflector (DBR). This coupling makes it possible to obtain plasmonic Tamm states, where excitation is possible at normal incidence and does not require the use of the Kretschmann configuration. Through parameters optimization of the gold nanostructured grating, we achieved well-defined and localized Tamm resonances between the gold nanostructured grating and the distributed Bragg reflector composed of SiO2/Si3N4 . To exploit the spatial confinement of the energy of the Tamm states in order to measure the change in refractive index, we propose three configurations, in which we substitute the last nitride layer in the Bragg reflector with porous materials. In the first configuration, we use a porous nitride portion with 30% porosity, producing sensitivity S=170 nm/RIU and figure of merit FOM=27.1 RIU-1 . In the second configuration, we use a porous nitride layer with a porosity of 30% ( S=175 nm/RIU and FOM=27.3 RIU-1 ). Finally, the third configuration adopts a 66% porous silicon layer ( S=268 nm/RIU and FOM=43.6 RIU-1 ). These values show the significant potential for sensing applications.

We numerically explore optical Tamm states (OTS) supported by a photonic structure composed of a nanostructured metallic layer on top of a distributed Bragg reflector (DBR). Several polarizations, incidences and patterning are assessed to map OTS and their properties. We then gain magnetic control of the OTS by adding a cobalt layer below the metal pattern and switching its magnetization. This control, widely used in plasmonics, takes advantage of the Transverse Magneto-Optical Kerr Effect (TMOKE). The simulated TMOKE signal of this structure has an amplitude of the order of 10 -3 and, compared to conventional magnetoplasmonic structures, provides high energy confinement between the metal stripes. In addition to the opening of the metallic layer that allows better access of the analyte to the sensitive area, this paves the way for higher sensitivities in bio- and chemical sensing applications.

In this paper, we present a detailed study of the effect of WO3 and Ni films in the presence of BP and BlueP-MDC nanomaterial layers on the sensitivity of a surface plasmon resonance (SPR) following the change in refractive index of the detection medium. Our nanostructure is based on the Kretschmann multilayer configuration composed of a BK7 prism, an Ag metallic film deposited on ZnO and a hybrid multilayer composed of WO3/Ni/2D-nanomaterials. In the first part, the study aims to optimize the effect of the thicknesses of the layers of the nanomaterials of the structure on the surface plasmon resonance. We obtain an angular sensitivity of the order of 480 deg/RIU for a figure of merit of 177.11 RIU−1 at the wavelength of 633 nm. These values are respectively 300% and 342% higher than those of a conventional SPR sensor (BK7/Ag/SM). After modeling the SPR biosensor studied in this paper, we showed how the plasmon resonance and sensitivity of the SPR sensor are affected by the refractive index of liquid biochemical elements. The proposed SPR structure can be used in highly sensitive urinary glucose detection and medical analysis applications.

A. bound state eigenfunction is defined here to be strictly localized within a subspace of the structure under study and has no decreasing behavior. Its eigenwavelength can be within state continua. Bound states in the continuum (BICs) and long-lived resonances have become a unique way to produce the extreme localization of electronic waves. We present a theoretical and numerical demonstration of semi-infinite bound states in the continuum (SIBICs) and long-lived resonances in a ringlike electronic microresonator coupled to a finite stub and to two electronic rib/ridge / ridge waveguides, together with their existence conditions. This structure is composed of a closed loop of length L , a finite stub of length L 1 and two semi-infinite leads. SIBICs localized in a semi- infinite subspace domain induce transmission zeros. Others induce transmission ones in the middle of longlived resonances. The BICs correspond to localized resonances of infinite lifetime inside the structure, without any leakage into the surrounding leads. When BICs exist within state continua, they induce Fano resonances exhibiting sharp peaks in the transmission spectra and in the variation of the density of states for specific values of the stub length L 1 . This enables one to regulate these resonances by means of this length. The obtained results take due account of the state number conservation between the final system and the reference one. This conservation rule enables one to find all the states of the final system and among them the bound in the continuum ones. The analytical results are obtained by means of the Green's function technique. The structures and the long-lived resonances presented in this paper may have potential applications due to their high sensitivities to weak perturbations, in particular in sensing, wave filtering, and microelectronic devices.

This paper presents a new biosensor design based on the Kretschmann configuration, for the detection of analytes at different refractive indices. Our studied design consists of a TiO2/SiO2 bi-layer sandwiched between a BK7 prism and a bimetallic layer of Ag/Au plasmonic materials, covered by a layer of black phosphorus placed below the analyte-containing detection medium. The different layers of our structure and analyte detection were optimized using the angular interrogation method. High performance was achieved, with a sensitivity of 240 deg/RIU and a quality factor of 34.7 RIU−1. This biosensor can detect analytes with a wide refractive index range between 1.330 and 1.347, such as glucose detection in urine samples using a refractive index variation of 10−3. This capability offers a wide range of applications for biomedical and biochemical detection and selectivity.

In this paper, we present a detailed study of the temperature effect (0 0 - 100 degrees C), degrees C ), on the plasmonic resonance and sensitivity of a surface plasmon resonance (SPR) to the medium detection refraction index change. We examine this SPR based on the Kretschmann multilayer configuration constituted by a BK7 prism, an Ag/Au bimetallic layer deposited on TiO2/SiO2 2 /SiO 2 and a BlueP/MoS2 2 heterostructure monolayer. First, a simple numerical calculation is provided to analyze the temperature effect on the plasmonic resonance. The model take into account the dependence on temperature of the refractive index of different materials composing the investigated structures. The main idea is to show how the sensitivity of the SPR based sensor is influenced according to operating temperature which is critical parameter when considering bio-sensing applications.