Search Results (17)

We theoretically investigated two types of nonlinear optical effects of photonic band edges (PBEs) in photonic crystals containing hyperbolic metamaterial (HMM) based on the intensity-dependent phase-variation compensation, where the HMM is composed of alternating the noble metal Ag with large-nonlinear-coefficient and dielectric material. Considering nonlinear conditions, the local field strength variation in nonlinear materials with the increase in the incident angle will lead to the movement of the PBE, resulting in two anomalous optical nonlinear effects. When the PBE is angle-independent under the linear condition, the PCs have angle-sensitive optical bistability and the critical threshold intensity always increases. However, if the PBE is designed to have angle dependence under linear conditions, the optical bistability in the PC can be angle-independent, and the critical threshold intensity is angle-independent over a wide range. This research provides important reference values for manufacturing direction-selectable devices that utilize different kinds of nonlinear optical effects. Full article

We study the collective spontaneous emission of two quantum emitters (QEs) placed near a semiconductor hyperbolic metamaterial (HMM) composed of a multilayer quantum well (MQW) and doped n⁺-In_0.53Ga_0.47As. The spontaneous emissions of two identical QEs in reflection and transmission configurations are both investigated in detail. It is found that the collective spontaneous emission is strongly dependent on whether there is strong coupling in the HMM or not. In the reflection configuration, the spontaneous emission changes more intensively with the transition wavelength of QEs when strong coupling is present compared to the situation without strong coupling. In the transmission configuration, the maximum spontaneous emission decay rate of two QEs can be obtained near the HMM for the given transition wavelength. In addition, the thickness of the HMM also has an important effect on the collective spontaneous emission in the transmission configuration. The results in this work have potential applications in the field of light-emitting devices, lasers, and quantum information processing. Full article

Graphene oxide (GO) has emerged as a carbon-based nanomaterial providing a different pathway to graphene. One of its most notable features is the ability to partially reduce it, resulting in graphene-like sheets through the elimination of oxygen-including functional groups. In this paper, the effect of localized interactions in an Ag/GO/Au multilayer system was studied to explore its potential for photonic applications. GO was dip-coated onto magnetron-sputtered silver, followed by the deposition of a thin gold film to form an Ag/GO/Au structure. Micro-Raman Spectroscopy, SEM and Variable Angle Ellipsometry (VASE) measurements were performed on the Ag/GO/Au structure. An interesting behavior of the GO deposited on magnetron-sputtered silver with the formation of Ag nanostructures on top of the GO layer is reported. In addition to typical GO bands, Micro-Raman analysis reveals peaks such as the 1478 cm⁻¹ band, indicating a transition from sp³ to sp² hybridization, confirming the partial reduction of GO. Additionally, calculations based on effective medium theory (EMT) highlight the potential of Ag/GO structures in hyperbolic metamaterials for photonics. The medium exhibits dielectric behavior up to 323 nm, transitions to type I HMM between 323 and 400 nm and undergoes an Epsilon Near Zero and Pole (ENZP) transition at 400 nm, followed by type II HMM behavior. Full article

Hyperbolic metamaterials (HMMs) are highly anisotropic materials with the unique property of generating electromagnetic modes. Understanding how these materials can be applied to control the propagation of light waves remains a major focus in photonics. In this study, we inserted a finite-size HMM rod into the point defect of two-dimensional photonic crystals (PhCs) and investigated the unique cavity modes of this hybrid system. The HMM enhances the efficiency of the cavity system in controlling light transmission. Numerical results demonstrate that the cavity modes based on HMMs can be categorized into various types, showing high Q-factors and promising potential for resonant modulation. Furthermore, the switching performance of the cavity with an HMM rod was examined, revealing that the finite-size HMM modes are highly frequency-sensitive and suitable for nonlinear controlled all-optical switching. These switches, characterized by low power consumption and high extinction ratios, are highly suitable for integration into photonic systems. Our investigation on the new type of HMM cavity illustrates that anisotropic materials can be effectively applied in cavity systems to generate highly efficient modes for filtering and switching. Full article

We introduce a groundbreaking plasmonic metamaterial, the Nano-Hemisphere on Hyperbolic Metamaterial (NHoHMM), which involves the fabrication of Ag nano-hemispheres on a multilayered Ag/SiO₂ structure, achieved solely through sputtering and heat treatment. Finite Difference Time Domain (FDTD) simulations unveil the intriguing slow propagation of the localized electric field, where light travels at only 1/40th of its usual speed within this structure. These simulations reveal distinctive sharp absorption peaks in the visible spectrum, attributed to surface plasmon resonance. In practical experiments, the NHoHMM structure, characterized by random Ag nano-hemispheres, exhibits broad absorption peaks spanning the visible range, rendering it a versatile broadband optical absorber. For comparison, the optical properties of the Ag nano-hemispheres on a nanocermet (NHoNC) structure were analyzed through simultaneous sputtering of Ag and SiO₂ followed by heat treatment. Simulations employing effective medium theory and the transfer matrix method demonstrate variable optical properties dependent on the Ag filling ratio in the nanocermet structure. The results obtained differ from the spectra of the NHoHMM structure; thus, it is concluded that in the NHoHMM structure, the calculated multi-peaks are broadened due to the inhomogeneity of the nano-hemispherical structure’s size, rather than the metal/dielectric multilayer structure being altered by the heat treatment. Full article

This study introduces an innovative integration of hyperbolic metamaterials (HMMs) and photonic crystals (PtCs), each possessing unique dispersion properties that effectively manipulate the propagation of light. We present a PtC waveguide consisting of arrays of HMM nanorods, denoted as HMM PtCs. This waveguide configuration enables the realization of a high figure of merit (FOM) nano-sensor. HMMs and PtCs share the same underlying physics. HMMs can generate surface plasmonics, while PtCs offer a bandgap for the waveguide. This configuration presents a novel sensing solution that directly couples surface plasmonics and waveguide modes. By modifying the refractive indices of the surrounding materials, the PtC waveguide exhibits alterations in absorption and transmission, allowing for the detection of temperature, pressure, and material variations. The refractive indices of the surrounding materials can be adjusted based on the sensor’s intended application. For instance, when the sensor is utilized for temperature sensing, thermal infrared materials can serve as the surrounding medium. As the temperature rises, the refractive index of the surrounding material changes accordingly, impacting the waveguide modes and thereby altering absorption and transmission. We utilized the finite element method to conduct numerical simulations in order to assess the absorption and transmission characteristics of the proposed system. Given that this approach involves a full electromagnetic calculation based on Maxwell’s equations, it closely approximates real-world scenarios. The employed numerical method demonstrates the remarkable performance of this proposed system, achieving a sensitivity of 324.16 nm/RIU (refractive index unit) and an impressive FOM of 469.58 RIU⁻¹. These results signify a substantial improvement over surface plasmonic sensors, which typically exhibit limited FOMs. The direct coupling between surface plasmonics and waveguide modes provides a distinct advantage, allowing the proposed sensor to deliver a superior performance. As a consequence, the HMM PtC waveguide sensor emerges as an exceptionally appealing option for photonic sensing applications. The complexity of the proposed system presents a fabrication challenge. Nevertheless, as fabrication technology continues to advance, we anticipate that this issue can be effectively resolved. The proposed HMM PtC waveguide holds vast potential across diverse fields, including biology, medicine, and clinics, representing an exciting advancement for both industry and scientific research. Full article

Current biosensors have limited application in clinical diagnostics as they lack the high order of specificity needed to detect low molecular analytes, especially in complex fluids (such as blood, urine, and saliva). In contrast, they are resistant to the suppression of non-specific binding. Hyperbolic metamaterials (HMMs) offer highly sought- after label-free detection and quantification techniques to circumvent sensitivity issues as low as 10⁵ M concentration in angular sensitivity. This review discusses design strategies in detail and compares nuances in conventional plasmonic techniques to create susceptible miniaturized point-of-care devices. A substantial portion of the review is devoted to developing low optical loss reconfigurable HMM devices for active cancer bioassay platforms. A future perspective of HMM-based biosensors for cancer biomarker detection is provided. Full article

In this work, we demonstrate, theoretically and experimentally, a hybrid dielectric-plasmonic multifunctional structure able to provide full control of the emission properties of CsPbI₃ perovskite nanocrystals (PNCs). The device consists of a hyperbolic metamaterial (HMM) composed of alternating thin metal (Ag) and dielectric (LiF) layers, covered by TiO₂ spherical MIE nanoresonators (i.e., the nanoantenna). An optimum HMM leads to a certain Purcell effect, i.e., an increase in the exciton radiative rate, but the emission intensity is reduced due to the presence of metal in the HMM. The incorporation of TiO₂ nanoresonators deposited on the top of the HMM is able to counteract such an undesirable intensity reduction by the coupling between the exciton and the MIE modes of the dielectric nanoantenna. More importantly, MIE nanoresonators result in a preferential light emission towards the normal direction to the HMM plane, increasing the collected signal by more than one order of magnitude together with a further increase in the Purcell factor. These results will be useful in quantum information applications involving single emitters based on PNCs together with a high exciton emission rate and intensity. Full article

We demonstrate a concept for the giant enhancement of the transverse magneto-optical Kerr effect (TMOKE) using bulk plasmon polariton (BPP) modes in non-magnetic multilayer hyperbolic metamaterials (HMMs). Since the BPP modes are excited through the attenuated total reflection (ATR) mechanism, using a Si-based prism-coupler, we considered a single dielectric magneto-optical (MO) spacer between the prism and the HMM. The working wavelength was estimated, using the effective medium approach for a semi-infinite dielectric-plasmonic multilayer, considering the region where the system exhibits type II HMM dispersion relations. Analytical results, by means of the scattering matrix method (SMM), were used to explain the physical principle behind our concept. Numerical results for giant TMOKE values (close to their maximum theoretical values, $\pm 1$) were obtained using the finite element method (FEM), applying the commercial software COMSOL Multiphysics. Our proposal comprises a simple and experimentally feasible structure that enables the study of MO phenomena in HMMs, which may find application in future nanostructured magnetoplasmonic metamaterials for active nanophotonic devices. Full article

Photonic hypercrystals (PHCs) are materials combining hyperbolic metamaterials (HMMs) with widely used photonic crystals. We found that finite-sized Type-I HMMs can support unique electromagnetic modes, which could be utilized in two-dimensional photonic crystals to achieve PHCs with twisted bands in the infrared region. Numerical investigation of the PHCs showed that the twisted bands have degenerate points that can support all-angle self-collimation effects. The behaviors of light beams change dramatically in such bands, which provides an effective method in controlling light propagation and can be applied as switching. The effect of the filling factor and the permittivity of the dielectric medium of the HMM on the twisted bands were studied. Furthermore, by considering the nonlinear effect of the dielectric layers, an all-optical switch working on the PHC twisted bands is proposed, which has low switching power and high extinction ratio (19.75 dB), superior to conventional HMM switches that require type transformation of metamaterial. Full article

Hyperbolic metamaterials (HMMs) exhibit high tunability in photonic devices. This study numerically investigates light propagation in photonic crystal (PhC) membranes containing HMMs. The proposed HMM PhC membranes contain square HMM rods, which comprise dielectric (Si) and metallic (Ag) layers. Owing to their property of subwavelength field localization, HMMs can be applied to PhCs to improve tunability and thus enhance the self-collimation (SC) effect of PhCs. The SC points were obtained in the second HMM PhC band, wherein the nearby dispersion curves change significantly. In addition, the effect of the HMM filling factor (i.e., the ratio of the metal-layer to unit-cell thicknesses) on the SC point frequency is studied. Finally, we demonstrate the efficient control of beam behaviors using HMM PhC membranes while considering the nonlinearity of Ag. The findings of this study confirm that high-performance HMM PhC membranes can be employed in nonlinear all-optical switches, filters, tunable lenses, and other integrated optical devices. Full article

In this work, we study the effect of spatial dispersion on propagation properties of planar waveguides with the core layer formed by hyperbolic metamaterial (HMM). In our case, the influence of spatial dispersion was controlled by changing the unit cell’s dimensions. Our analysis revealed a number of new effects arising in the considered waveguides, which cannot be predicted with the help of local approximation, including mode degeneration (existence of additional branch of TE and TM high-β modes), power flow inversion, propagation gap, and plasmonic-like modes characterized with long distance propagation. Additionally, for the first time we reported unusual characteristic points appearing for the high-β TM mode of each order corresponding to a single waveguide width for which power flow tends to zero and mode stopping occurs. Full article

We theoretically study the multiple sharp Fano resonances produced by the near-field coupling between the multipolar narrow plasmonic whispering-gallery modes (WGMs) and the broad-sphere plasmon modes supported by a deep-subwavelength spherical hyperbolic metamaterial (HMM) cavity, which is constructed by five alternating silver/dielectric layers wrapping a dielectric nanosphere core. We find that the linewidths of WGMs-induced Fano resonances are as narrow as 7.4–21.7 nm due to the highly localized feature of the electric fields. The near-field coupling strength determined by the resonant energy difference between WGMs and corresponding sphere plasmon modes can lead to the formation of the symmetric-, asymmetric-, and typical Fano lineshapes in the far-field extinction efficiency spectrum. The deep-subwavelength feature of the proposed HMM cavity is verified by the large ratio (~5.5) of the longest resonant wavelength of WGM_1,1 (1202.1 nm) to the cavity size (diameter: 220 nm). In addition, the resonant wavelengths of multiple Fano resonances can be easily tuned by adjusting the structural/material parameters (the dielectric core radius, the thickness and refractive index of the dielectric layers) of the HMM cavity. The narrow linewidth, multiple, and tunability of the observed Fano resonances, together with the deep-subwavelength feature of the proposed HMM cavity may create potential applications in nanosensors and nanolasers. Full article

We propose a hyperbolic metamaterial-based surface plasmon resonance (HMM-SPR) sensor by composing a few pairs of alternating silver (Ag) and zinc oxide (ZnO) layers. Aiming to achieve the best design for the sensor, the dependence of the sensitivity on the incidence angle, the thickness of the alternating layer and the metal filling fraction are explored comprehensively. We find that the proposed HMM-SPR sensor achieves an average sensitivity of 34,800 nm per refractive index unit (RIU) and a figure of merit (FOM) of 470.7 RIU⁻¹ in the refractive index ranging from 1.33 to 1.34. Both the sensitivity (S) and the FOM show great enhancement when compared to the conventional silver-based SPR sensor (Ag-SPR). The underlying physical reason for the higher performance is analyzed by numerical simulation using the finite element method. The higher sensitivity could be attributed to the enhanced electric field amplitude and the increased penetration depth, which respectively increase the interaction strength and the sensing volume. The proposed HMM-SPR sensor with greatly improved sensitivity and an improved figure of merit is expected to find application in biochemical sensing due to the higher resolution. Full article

Hereby, we present an optical isolator (optical diode) based on a hyperbolic metamaterial (HMM). We demonstrate that a grating-free planar linear non-magnetic HMM structure deposited on a high-index substrate, which, due to presence of strong spatial dispersion (non-locality), reveals asymmetrical transmittance and reflectance characteristics for light of arbitrary polarization within a wide angular and spectral range. The presented device may be efficiently utilized to completely block backward and enforce unidirectional propagation in free space and integrated systems without the use of magnetooptical or non-linear effects. Full article