Extraordinary Optical Transmission Phenomenon Research Articles

INNV-05. DEVELOPMENT OF A LABEL-FREE PLASMONIC OPTICAL BIOSENSOR FOR INTRAOPERATIVE DETECTION OF TUMOR TISSUE IN GLIOBLASTOMA

Abstract Safe maximal resection of patients with glioblastoma remains a surgical challenge due to the invasive nature of the tumor and the difficulty in distinguishing tumor margins during resection. Several tools are currently used for this purpose, such as, confocal laser endomicroscopy and fluorescence-guided surgery. In this context, biosensors based on plasmonic technology using the extraordinary optical transmission (EOT) phenomenon can help to distinguish between tumor and surrounding tissue based on their optical properties. We developed a biosensor utilizing EOT through a nanostructured gold matrix with 220 nm diameter holes and conducted a prospective study in 35 GBM patients. Paired samples of tumor and peritumoral tissue were collected during surgery. Each sample’s optical imprint was analyzed, revealing significant differences in refractive indices (RI). Tumor tissue showed higher RI values (1.350, IQR 1.344–1.363) compared to peritumoral tissue (1.341, IQR 1.339–1.349) with a p-value of 0.0047. The receiver operating characteristic (ROC) curve indicated the biosensor’s ability to differentiate the tissues (AUC = 0.8779, p < 0.0001). An optimal RI cut-off point of 0.003 was determined, with the biosensor achieving 81% sensitivity and 80% specificity. Our results indicate that this plasmonic technology-based biosensor could have a significant impact on the surgical treatment of glioblastoma by providing a label-free tool for tumor margin discrimination and improving the accuracy of glioblastoma surgery. Future research will focus on optimizing the nanoarchitecture of the biosensor to further improve its sensitivity and specificity, as well as exploring its applicability to other cancer types by analyzing the biomarkers responsible for the different RIs of the footprints.

Visible Light-Illuminated Gold Nanohole Arrays With Tunable On-Chip Plasmonic Sensing Properties

Since the discovery of the extraordinary optical transmission phenomenon, nanohole arrays have attracted much attention and been widely applied in sensing. However, their typical fabrication process, utilizing photolithographic top-down manufacturing technologies, has intrinsic drawbacks including the high costs, time consumption, small footprint, and low throughput. This study presented a low-cost, high-throughput, and scalable method for fabricating centimeter-scale (1×2 cm2) nanohole arrays using the improved nanosphere lithography. The large-scale close-packed polystyrene monolayers obtained by the hemispherical-depression-assisted self-assembly method were employed as colloidal masks for the nanosphere lithography, and the nanohole diameter was tuned from 233 nm to 346 nm with a fixed period of 420 nm via plasma etching. The optical properties and sensing performance of the nanohole arrays were investigated, and two transmission dips were observed due to the resonant coupling of plasmonic modes. Both dips were found to be sensitive to the surrounding environment, and the maximum bulk refractive index sensitivity was up to 162.1 nm/RIU with a 233 nm hole diameter. This study offered a promising approach for fabricating large-scale highly ordered nanohole arrays with various periods and nanohole diameters that could be used for the development of low-cost and high-throughput on-chip plasmonic sensors.

All-optical control of ultrafast plasmon resonances in the pulse-driven extraordinary optical transmission

Understanding ultrafast processes in their natural timescale is crucial for controlling and manipulating nanoscale optoelectronic devices under light–matter interaction. Here, we demonstrate that ultrafast plasmon resonances, attributed to the phenomenon of extraordinary optical transmission (EOT), can be significantly modified by tuning the spectral and temporal properties of the ultrashort light pulse. In this scheme, all-optical active tuning governs the spatial and temporal enhancement of plasmon oscillations in the EOT system without device customization. We analyze the spectral and temporal evolution of the system using two approaches. First, we develop a theoretical framework based on the coupled harmonic oscillator model, which analytically describes the dynamics of plasmon modes in the coupled and uncoupled states. Later, we compare the evolution of the system under continuous-wave and pulsed illumination. Further, we discuss the time-resolved spectral and spatial dynamics of plasmon modes using a 3D finite difference time-domain simulation method and wavelet transform. Our results show that optical tuning of the oscillation time, intensity, and spectral properties of propagating and localized plasmon modes yields a three-fold enhancement in the EOT signal. The active tuning of the EOT sensor through ultrashort light pulses paves the way for the development of on-chip photonic devices employing high-resolution imaging and sensing of abundant atomic and molecular systems.

A Novel Analysis for Light Patterns in Nano Structures

Nano antennas have a significant role in photonic nanodevices due to the ability of concentrating radiation in a small space region. The confined fields present a high sensitivity to the used materials in that regions. The electromagnetic wave models of nanoantennas usually operate in the frequency domain. However, electromagnetic wave models in the time domain are just as important and more advantageous, for example, in light pulses propagation. In this article, a new stochastic method based on the ray model of light in absorbing media is presented and light patterns on a target near a nanoantenna are obtained. The optical properties of the materials are described by their complex refractive index. When dealing with photons in the time domain, this formulation allows the calculation of the probability of a given photon movement. Different patterns, obtained with the new method, are compared with a Finite Element Tool ones, leading to model validation. The simulated structure included an aperture nanoantenna. With this method, the results show the light confinement and the extraordinary optical transmission phenomenon, meaning some photons on the target are refracted and re-transmitted by the metal. Thus, the output beam is more intense than the transmitted directly by the apertures.

A New Method to Analyse the Role of Surface Plasmon Polaritons on Dielectric-Metal Interfaces

At nano-scale new phenomena have been discovered, allowing devices’ miniaturisation, energy harvesting, and power reduction. The Extraordinary Optical Transmission (EOT) phenomenon was reported in 1998 by Ebessen, who stated that the resonant peaks in the response of metallic nano antennas were more intense than predicted by classical diffraction theories. Years later, the main reason for this behaviour was attributed to the Surface Plasmon Polaritons (SPP), at least in ultraviolet and visible regions. In this article, a new method to model the radiation-matter interaction on a dielectric-metal interface is proposed, based on Maxwell’s equations and Fresnel Coefficients in absorbing media. Transmission percentage, angle and propagation length are obtained for a rigorous sweep on incident angle and wavelength. The results taken using some noble metals allow us to observe the presence of surface phenomena at expected SPP resonances. First, it is noticeable huge values of transmission in ultraviolet and visible regions, meaning that the metal does not reflect all the radiation. Also, the transmission angle tends to be higher, meaning huge surface components. Furthermore, the transmission length is on orders of 50-100 nm, meaning that phenomena as EOT only occurs at the nano-scale, since waves should arrive at another interface before being absorbed.

두 가지 개구구조의 투과 단면적에 대한 일반적인 표현식의 타당성: 단일 공진 개구 구조와 비공진 개구의 유한 주기구조

For an electromagnetic plane wave that is normally incident upon an aperture or aperture array in an infinite perfectly electrical conducting plane, the validity of the general expression for the transmission cross-section as a measure of the transmitted power through the aperture or aperture array is investigated for the following two cases: first, for a single transmission resonant aperture (TRA) such as a complementary split ring resonator, which is larger than Bethe’s small magnetic dipole; second, for the finite periodic array of a non-TRA such as the usual circular or rectangular apertures aligned along the E-plane direction corresponding to the parallel configuration in terms of the terminology of the electrical dipole array theory. To validate the investigation, the proposed expression is applied to a general aperture distribution, and the results are compared with the results obtained using the Rao–Wilton–Glisson method for the above two cases of aperture distributions. Consequently, it is discovered that for the finite array of non-TRAs, the E-plane aperture array produces an improved directive for the field than the H-plane aperture array used as the Huygens source. This observation may aid in understanding the underlying physics of the two-slot model for rectangular microstrip antennas and the basic 1D linear array as a minimal system exhibiting the extraordinary optical transmission phenomena in 2D aperture arrays.

Extraordinary optical transmission from a thin microcavity by macroscopic quantum effect

The macroscopic quantum effect is revealed to elaborate the extraordinary optical transmission (EOT) from a subwavelength thin microcavity based on the uncertainty property of the transmitted electromagnetic fields after the aperture. A critical radius is found in the thin microcavity under a certain incident electromagnetic wavelength. With the aperture radius varying, the transmitted field can be divided into three regimes: I) the macroscopic quantum regime when the aperture radius is less than the critical radius, in which the field edge effect occurs and the EOT phenomenon is perfectly manifested; II) the wave-particle duality regime in the vicinity of the critical radius, in which the edge effect and diffraction phenomenon exist simultaneously; III) the wave regime when the aperture radius is greater than the critical radius, in which the near-field diffraction emerges. In addition, the influences of incident wavelength and microcavity thickness on EOT are also investigated. Our research has potential applications in advanced optical devices, such as light switch and optical manipulations.

Engineering the Optical Response of the Novel Plasmonic Binary Nanohole Array

The phenomenon of extraordinary optical transmission (EOT) due to its advantages has been considered by researchers in various applications, and in recent years, many efforts have been made to engineer these structures to get the best possible response for desired applications. In this work, the optical properties of novel binary gold nanohole arrays are investigated theoretically. We engineered the optical response of the system by adjusting the ratio of contribution of surface plasmon polariton (SPP) to localized surface plasmon resonance (LSPR) through the manipulation of the geometrical properties. The changes in the topology of this nanohole array affected the intensity and the wavelength of transmission peaks. The sensitivity of the optical response to the refractive index was also investigated. The designed structure is a good candidate for use as a polarization-independent optical label-free sensor.

A Plasmonic Infrared Multiple-Channel Filter Based on Gold Composite Nanocavities Metasurface.

A plasmonic near-infrared multiple-channel filter is numerically and experimentally investigated based on a gold periodic composite nanocavities metasurface. By the interference among different excited plasmonic modes on the metasurface, the multipeak extraordinary optical transmission (EOT) phenomenon is induced and utilized to realize multiple-channel filtering. Investigated from the simulated transmission spectrum of the metasurface, the positions and intensity of transmission peaks are tuned by the geometrical parameters of the metasurface and environmental refractive index. The fabricated metasurface approached transmission peaks at 1128 nm, 1245 nm, and 1362 nm, functioning as a three-passbands filter. With advantages of brief single-layer fabrication and multi-frequency selectivity, the proposed plasmonic filter has potential possibilities of integration in nano-photonic switching, detecting and biological sensing systems.

Tunable and multifunctional terahertz devices based on one-dimensional anisotropic photonic crystals containing graphene and phase-change material.

In the past few years, designing tunable and multifunctional terahertz devices has become a hot research area in terahertz science and technology. In this work, we report a study on one-dimensional anisotropic photonic crystals (1D APCs) containing graphene and phase-change material VO2. We numerically demonstrate the band-pass filtering, perfect absorption, comb-shaped extraordinary optical transmission and Fano-like resonance phenomenon in pure 1D APCs and 1D APCs with a VO2 defect layer under different conditions of a tangential wave vector. The performance of these phenomena in the terahertz region can be modulated by changing the chemical potential of graphene. The band-pass filter and perfect absorber functions of 1D APCs with a VO2 defect layer can be freely switched by changing the phase of VO2. We employ the equivalent-permittivity model and dispersion-relation equation to give reasonable explanations on these behaviors.

Bimodal Plasmonic Color Filters Enable Direct Optical Imaging of Ion Implantation in Thin Films

AbstractOptical metamaterials offer precise control over the properties and interactions of light at the nanoscale, attracting interest in many new fields of research including chemical and molecular sensing, magnetic antennas, and photovoltaic elements. By utilizing the phenomenon of extraordinary optical transmission (EOT) plasmonic devices enable the detection of minute changes in the local, near‐surface, dielectric properties of materials, opening up a wide range of different applications. Characterization of the optoelectronic properties of ultra‐thin films is of paramount importance for a wide range of electronic applications including integrated circuit production. However, it is often extremely difficult to achieve using conventional imaging techniques. Here, it is demonstrated that plasmonic color filters can be used for the direct optical imaging and characterization of ion implantation in thin films. A model system consisting of variable doses of gallium ions implanted within titanium oxide thin films is used. It is observed that the ion implantation dose leads to a variation in the measured plasmon resonance spectra, which can be further enhanced through the use of bimodal nanopixel arrays. Using Monte Carlo simulations and the Maxwell‐Garnett relation, the observed plasmon resonance spectra in terms of the gallium ion implantation dose is quantitatively interpreted.

Multi-cycle reconfigurable THz extraordinary optical transmission using chalcogenide metamaterials

Metamaterials composed of metallic antennae arrays are used as they possess extraordinary optical transmission (EOT) in the terahertz (THz) region, whereby a giant forward light propagation can be created using constructive interference of tunneling surface plasmonic waves. However, numerous applications of THz meta-devices demand an active manipulation of the THz beam in free space. Although some studies have been carried out to control the EOT for the THz region, few of these are based upon electrical modulation of the EOT phenomenon, and novel strategies are required for actively and dynamically reconfigurable EOT meta-devices. In this work, we experimentally present that the EOT resonance can be coupled to optically reconfigurable chalcogenide metamaterials which offers a reversible all-optical control of the THz light. A modulation efficiency of 88% in transmission at 0.85 THz is experimentally observed using the EOT metamaterials, which is composed of a gold (Au) circular aperture array sitting on a non-volatile chalcogenide phase change material (Ge₂Sb₂Te₅) film. This comes up with a robust and ultrafast reconfigurable EOT over 20 times of switching, excited by a nanosecond pulsed laser. The measured data have a good agreement with finite-element-method numerical simulation. This work promises THz modulators with significant on/off ratios and fast speeds.

Enhanced transmission through a Si-InSb-Si bimaterial subwavelength grating with slits at the terahertz range.

Two groups of grating structures with subwavelength slits, composed of different materials are investigated to realize an extraordinary optical transmission (EOT) phenomenon. We find that the transmittance of a InSb grating at the frequencies corresponding to surface plasmon (SP) excitation is almost zero, which verifies the negative role of SPPs in transmission anomalies. And optical characteristics of these bimaterial grating structures are thoroughly analyzed by the transmittance spectrum and optical field intensity. In addition, the greatly enhanced transmission was achieved by changing the temperature, doping concentration, and the geometrical parameters of the InSb-Si-InSb bimaterial grating structure, and the optimized transmission can reach almost 94%. Besides, it is verified that the position of the peaks is strongly dependent on the depth of the slits. Last, we demonstrate the transmission of the InSb-Si-InSb bimaterial grating is higher than its counterparts, and the collimated beaming effect is also realized through it. These features make this structure an excellent candidate for plasmonic components in all optical and optoelectronic fields.

Investigating extraordinary optical transmission and sensing performance through periodic bilayer magneto-plasmonic structure

This paper proposes the phenomenon of extraordinary optical transmission via a magneto-plasmonic nanostructure, which combines magnetic and plasmonic functionalities. The structure includes an active magnetic film magnetized perpendicular to its surface and a plasmonic metal film, perforated with subwavelength circular annular arrays, with a ring placed in the middle of each annular circle. We use the finite element method and the finite-difference time-domain method for simulation of the structure. Numerical analysis shows an improvement in the Faraday rotation and optical transmission, simultaneously, in a magneto-plasmonic structure based on a silver- and bismuth-substituted ferrite garnet. Simultaneous improvement is achieved by coupling the TE and TM waveguide-plasmon modes. The amount of enhancement is adjusted by changing the dimensions, the periodicity of the hole arrays, and the refractive index of the materials filled in the holes. The influence of excitation of the two kinds of plasmon modes and the application of the external magnetic field are used to enhance the optical response. The resulting investigation shows two resonance peaks in the near-infrared range of the Faraday effect spectrum. Because of the strong Faraday rotation coinciding with the dual-band transmission of approximately 90%, the maximum figure of merit can also be obtained. Finally, this structure is investigated as a sensor in different reflective indexes from 1 to 1.5 RIU, and sensitivity of 45.97 nm/RIU was achieved. The potential applications of these nanostructures include, for example, subwavelength optics, optoelectronic devices, biosensing devices, and magneto-optical devices.

Extraordinary optical transmission through titanium nitride-coated microsphere lattice

Titanium nitride (TiN), one candidate as an alternative plasmonic material, is deposited by the sputtering method on top of a self-assembled polystyrene microsphere lattice. The optical transmission spectra of the TiN-coated microsphere lattice reveal a transmission pass-band attributed to the extraordinary optical transmission phenomenon, known from subwavelength hole arrays in metal films. Simulations by finite element method show the presence of a hybrid mode resulting from coupling of surface plasmons on the TiN film to photonic guided resonance modes in the dielectric microsphere lattice. The crucial role of the microspheres in the transmission process is also evidenced by dedicated simulations. Such hybrid colloidal photonic-plasmonic crystals based on TiN are promising for future plasmonic applications requiring the thermo-mechanical stability of refractory ceramics complemented by a plasmonic efficiency similar to that of gold, but also for extending the range of current applications beyond the use of the classical noble metals gold and silver.

Fast response and high responsivity realization of microcavity enhanced graphene photodetector using subwavelength grating electrodes

Graphene photodetectors (GPD) have been studied since the first discovery of graphene, and microcavity enhanced graphene photodetector (MEGPD) is one of the structure of GPDs with many advantages. Additionally, MEGPDs can reach fast response with well-designed electrode structure. Subwavelength grating (SWG) shows extraordinary optical transmission (EOT) phenomenon, making it a potential structure for MEGPD electrodes. Responsivity of MEGPD can be kept at its origin value due to high transmittance of SWG structure while response time of MEGPD could be significantly reduced. In this paper, a design and analysis of MEGPD with SWG electrodes is presented. Theoretical analysis shows that structure parameters including period, height and width of slits are the key factors to influence both the transmittance and response time. Silver is selected as the material of electrodes to obtain high conductivity. Transmittance is determined through a transmission model of SWG structure. SWG structure is confirmed through optimization, and the result is presented below: The period is 730 nm, the height is 580 nm and the width of slits is 330 nm. At a nominal operating wavelength of 1.55μm, the transmittance can reach 0.9927 to maintain the responsivity at 1.23A/W and the response time can reach picoseconds. This design may provide an idea to gain high response speed when fabricating high responsivity GPD.

Enhanced extraordinary optical transmission and refractive-index sensing sensitivity in tapered plasmonic nanohole arrays

The phenomenon of extraordinary optical transmission (EOT) caused by light through metallic nanohole arrays has attracted significant attention due to its potential applications for monolithic color filters and ultrasensitive label-free biosensing. However, the EOT spectra of these nanohole arrays have multiple resonance peaks that are spectrally close to each other due to the multiple resonance modes generated by different media on the upper and lower surfaces of metal. In addition, owing to the absorption loss of metal and the scattering of holes, the EOT resonance peaks have low transmission coefficient for practical applications. In this work, utilizing a tapered nanohole arrays structure which is stacked by multiple cylindrical holes with the same depth but different radii, we show that tapered nanohole arrays can effectively suppress the excitation of multiple resonance peaks, and a single EOT peak emerges in the transmission spectrum and simultaneously exhibits significantly enhanced transmission (∼7 times) and narrow linewidth (∼15 nm). The enhanced EOT of tapered nanohole arrays can be also found in other wavelength regions and plasmonic materials. Benefiting from isolated transmission peak, high transmission efficiency and extremely narrow linewidth, a highly sensitive plasmonic nanosensor with sensitivity of 1580 nm/RIU and figure of merit of 105 can be attained. We believe that the tapered nanohole structure would enable applications for ultrasensitive sensors, switches and efficient filters.

Modeling of Refractive Index Sensing Using Au Aperture Arrays on a Bragg Fiber Facet

A finite-difference-time-domain (FDTD) approach is undertaken to investigate the extraordinary optical transmission (EOT) phenomenon of Au circular aperture arrays deposited on a Bragg fiber facet for refractive index (RI) sensing. Investigation shows that the choice of effective indices and modal loss of the Bragg fiber core modes will affect the sensitivity enhancement by using a mode analysis approach. The critical parameters of Bragg fiber including the middle dielectric RI, as well as its gap between dielectric layers, which affect the EOT and RI sensitivity for the sensor, are discussed and optimized. It is demonstrated that a better sensitivity of 156 ± 5 nm per refractive index unit (RIU) and an averaged figure of merit exceeding 3.5 RIU−1 are achieved when RI is 1.5 and gap is 0.02 μm in this structure.

Optical inspection of manufactured nanohole arrays to bridge the lab-industry gap

Metallic nanohole arrays have shown their potential as sensing tools. Important research supported by sophisticated laboratory experiments have been recently carried out, that may help to develop practical devices to be implemented in the real life. To get this goal, the gap between industry and technology at the nanoscale level must be overcome. One of the major drawbacks is the quality inspection of the manufactured nanostructured surfaces to ensure a reliable sensing. In this paper we introduce an optical method, based on the Extraordinary Optical Transmission phenomenon, for an inspection of such surfaces at industrial level. Unlike usual techniques like scanning electron microscopy, our method gives at the same time, a quick map of the surface homogeneity together with its local plasmonic performance. Our results show that this method is reproducible and reliable as to give a “seal of identification” and quality guarantee of the manufactured surface as basic element of a sensing device.

Application of Sub-wavelength Grating Electrodes in Photo Conductive Antennas

Terahertz waves have great scientific value and broad application prospects, in which the key technology is the generation of terahertz waves. Photoconductive antennas (PCA) are one of the main methods to generate terahertz waves, but lower radiation efficiency limits the further development. A sub-wavelength grating electrode structure is utilized, which employ extraordinary optical transmission (EOT) phenomenon, to enhance photoelectric conversion efficiency, therefor generating high-power, high-energy terahertz wave. First, groove-slit transmission is analyzed to guide the design of grating electrode. Then, parameters of sub-wavelength grating electrode are analyzed and optimized under 2D, which is compared with traditional and plasma PCA. Results show that the sub-wavelength grating electrode can significantly enhance the transmission field.