Search

Hyperuniform disordered solids (HUDS) waveguides, a type of emerging artificial photonic bandgap (PBG) devices, are demonstrated to possess large, complete, and isotropic PBGs, being promising for developing applications in optoelectronics, nonlinear optics, and sensing. However, optical losses of HUDS waveguides are usually limited by giant light scattering from the irregular distribution of HUDS cells. Herein, HUDS waveguide devices are demonstrated with low optical losses and large PBGs by exploring a morphology‐engineering and wall‐network‐regulation method of developing HUDS structures. The results show that the proposed device can achieve a 3.0 dB transmittance improvement for a 36‐µm‐long silicon HUDS waveguide. Based on the proposed HUDS structure, a waveguide‐coupled HUDS‐cladding nanocavity is also demonstrated with a quality factor of ≈70 at 2.250 µm wavelengths and a theoretical refractive index sensitivity of 446 nm RIU−1. The study opens an avenue to develop intriguing HUDS waveguide devices for on‐chip applications. [ABSTRACT FROM AUTHOR]

This study introduces the creation, simulation, and assessment of a 2-D photonic crystal refractive index biomedical sensor, enriched with intricate design considerations. The focal point of the design process revolves around achieving exceptional sensitivity, high-quality factor, and an impressively compact multi-type cancer sensor. The proposed approach involves the development of a nanocavity photonic crystal waveguide, embellished with double circle hole defects and an arrangement of silicon rods in a hexagonal lattice pattern. This sensor is designed to effectively differentiate between normal cells and six distinct categories of cancerous cells, namely Jurkat, Hela, PC-12, MDA-MB-231, MCF-7, and Basal (which pertains to skin cancer). The proposed design provide remarkable sensitivity, ultra-quality factor and compactness for healthy cell 455.33 nm/RIU, 7199.86, 9.4 × 5.5 µm2 respectively. The investigation employs both the finite difference time domain method and the plane wave expansion methods to meticulously analyze and simulate the suggested biosensor design. Furthermore, a comprehensive comparative analysis is conducted, between the current work with literature concerning cancer-centric refractive index photonic crystal sensors. This endeavor is undertaken to validate and underscore the credibility and efficacy of the proposed design. [ABSTRACT FROM AUTHOR]

A fully quantum, numerically accurate methodology is presented for the simulation of the exciton dynamics and time-resolved fluorescence of cavity-tuned two-dimensional (2D) materials at finite temperatures. This approach was specifically applied to a monolayer WSe2 system. Our methodology enabled us to identify the dynamical and spectroscopic signatures of polaronic and polaritonic effects and to elucidate their characteristic timescales across a range of exciton–cavity couplings. The approach employed can be extended to simulation of various cavity-tuned 2D materials, specifically for exploring finite temperature nonlinear spectroscopic signals. [ABSTRACT FROM AUTHOR]

As the driving source, highly efficient silicon-based light emission is urgently needed for the realization of optoelectronic integrated chips. Here, we report that enhanced green electroluminescence (EL) can be obtained from oxygen-doped silicon nitride (SiNx:O) films based on an ordered and tunable Ag nanocavity array with a high density by nanosphere lithography and laser irradiation. Compared with that of a pure SiNxO device, the green electroluminescence (EL) from the SiNx:O/Ag nanocavity array device can be increased by 7.1-fold. Moreover, the external quantum efficiency of the green electroluminescence (EL) is enhanced 3-fold for SiNx:O/Ag nanocavity arrays with diameters of 300 nm. The analysis of absorption spectra and the FDTD calculation reveal that the localized surface plasmon (LSP) resonance of size-controllable Ag nanocavity arrays and SiNx:O films play a key role in the strong green EL. Our discovery demonstrates that SiNx:O films coupled with tunable Ag nanocavity arrays are promising for silicon-based light-emitting diode devices of the AI period in the future. [ABSTRACT FROM AUTHOR]

Lasers are ubiquitous for information storage, processing, communications, sensing, biological research and medical applications. To decrease their energy and materials usage, a key quest is to miniaturise lasers down to nanocavities. Obtaining the smallest mode volumes demands plasmonic nanocavities, but for these, gain comes from only a single or few emitters. Until now, lasing in such devices was unobtainable due to low gain and high cavity losses. Here, we demonstrate a form of 'few emitter lasing' in a plasmonic nanocavity approaching the single-molecule emitter regime. The few-emitter lasing transition significantly broadens, and depends on the number of molecules and their individual locations. We show this non-standard few-emitter lasing can be understood by developing a theoretical approach extending previous weak-coupling theories. Our work paves the way for developing nanolaser applications as well as fundamental studies at the limit of few emitters. [ABSTRACT FROM AUTHOR]

Plasmonic nanocavities form very robust sub-nanometer gaps between nanometallic structures and confine light within deep subwavelength volumes to enable unprecedented control of light–matter interactions. However, spherical nanoparticles acquire various polyhedral shapes during their synthesis, which has a significant impact in controlling many light–matter interactions, such as photocatalytic reactions. Here, we focus on nanoparticle-on-mirror nanocavities built from three polyhedral nanoparticles (cuboctahedron, rhombicuboctahedron, decahedron) that commonly occur during the synthesis. Their photonic modes have a very intricate and rich optical behaviour, both in the near- and far-field. Through a recombination technique, we obtain the total far-field produced by a molecule placed within these nanocavities, to reveal how energy couples in and out of the system. This work paves the way towards understanding and controlling light–matter interactions, such as photocatalytic reactions and non-linear vibrational pumping, in such extreme environments.

As the driving source, highly efficient silicon-based light emission is urgently needed for the realization of optoelectronic integrated chips. Here, we report that enhanced green electroluminescence (EL) can be obtained from oxygen-doped silicon nitride (SiNx:O) films based on an ordered and tunable Ag nanocavity array with a high density by nanosphere lithography and laser irradiation. Compared with that of a pure SiNxO device, the green electroluminescence (EL) from the SiNx:O/Ag nanocavity array device can be increased by 7.1-fold. Moreover, the external quantum efficiency of the green electroluminescence (EL) is enhanced 3-fold for SiNx:O/Ag nanocavity arrays with diameters of 300 nm. The analysis of absorption spectra and the FDTD calculation reveal that the localized surface plasmon (LSP) resonance of size-controllable Ag nanocavity arrays and SiNx:O films play a key role in the strong green EL. Our discovery demonstrates that SiNx:O films coupled with tunable Ag nanocavity arrays are promising for silicon-based light-emitting diode devices of the AI period in the future.

Two-dimensional (2D) heterostructures integrated into nanophotonic cavities have emerged as a promising approach towards novel photonic and opto-electronic devices. However, the thickness of the 2D heterostructure has a strong influence on the resonance frequency of the nanocavity. For a single cavity, the resonance frequency shifts approximately linearly with the thickness. Here, we propose to use the inherent non-linearity of the mode coupling to render the cavity mode insensitive to the thickness of the 2D heterostructure. Based on the coupled mode theory, we reveal that this goal can be achieved using either a homoatomic molecule with a filtered coupling or heteroatomic molecules. We perform numerical simulations to further demonstrate the robustness of the eigenfrequency in the proposed photonic molecules. Our results render nanophotonic structures insensitive to the thickness of 2D materials, thus owing appealing potential in energy- or detuning-sensitive applications such as cavity quantum electrodynamics.

Designed hexagonal ZnIn 2 S 4 nanosheets wrapped oxygen deficient blue TiO 2 (B) catalyst for highly stable and selective CO 2 Photoreduction into CO and CH 4. The advanced photoactivity is attributed due to improved CO 2 absorption capacity, electron mobility, and visible light accessibility, resulting in effective charge carrier separation and transfer process. [Display omitted] • Simple approaches were used to develop nanocavity assisted oxygen deficient blue TiO 2 (B) nanorods (BT) and ZnIn 2 S 4 nanosheets. • Exfoliating bulk ZnIn2S4 nanosheets into a few layers (ZIS) and integrating them on BT generates a BT/ZIS composite. • The integration of BT on ZIS accelerates charge separation and migration due to high absorption capacity and well-matched band potentials. • The optimized BT/ZIS has a high CO 2 conversion rate into CO and CH 4 , as well as great selectivity and durability. Developing new and highly stable efficient photocatalysts is crucial for achieving high performance and selective photocatalytic CO 2 conversion. In this paper, we designed a one-dimensional oxygen-deficient blue TiO 2 (B) (BT) catalyst for improved electron mobility and visible light accessibility. In addition, hexagonal ZnIn 2 S 4 (ZIS) nanosheets with a low bandgap and great visible light accessibility are employed to produce effective heterostructures with BT. The synthesized materials are tested for photocatalytic conversion of CO 2 into solar fuels (H 2 , CO and CH 4). The optimized composite yields 71.6 and 10.3 μmol g−1h−1 of CO and CH 4 , three and ten times greater than ZIS, respectively. When ZIS nanosheets are combined with a one-dimensional oxygen-deficient BT catalyst, improved electron mobility and visible light accessibility are achieved, charge carriers are effectively segregated, and the transfer process is accelerated, resulting in efficient CO 2 reduction. The photocatalytic CO 2 conversion activity of the constructed BT/ZIS heterostructures is very stable over a 10-day (240-hour) period, and CO and CH 4 production rates increase linearly with time; however, as time goes on, the rates of H 2 production decrease. Further, a five-time recycling test confirmed this, revealing essentially equal activity and selectivity throughout the experiment. As a result, CO 2 to CO and CH 4 conversion has high selectivity and longer durability. The band structure of the BT/ZIS composite is determined using Mott-Schottky measurement, diffuse reflectance spectroscopy, and valence band X-ray photoelectron spectroscopy. This research demonstrates a novel approach to investigating effective, stable, and selective photocatalytic CO 2 reduction systems for solar-to-chemical energy conversion. [ABSTRACT FROM AUTHOR]

Refractive index (RI) can be used to identify a particular substance and determine its purity and concentration. The RI of glucose solution with various concentrations can be determined using a distributed Bragg reflective (DBR) device containing a nanocavity. The optical property of the reflection spectrum produced by DBR is sensitive to the variation of the refractive index. In this study, a DBR with a cavity width of 220 nm, located in the middle of the device, is designed and used to sense the variation in the refractive index of glucose at different concentrations. The proposed design showed a sharp dip pattern within the reflection spectrum. The wavelength of the absorption peak was found to be sensitive to trivial variations in the refractive index of glucose solution. Results showed that the variation in the refractive index of glucose within the order of Δn = 0.02 has led to a noticeable shift in the absorption spectrum by Δλ = 2.6 nm. Furthermore, the sensitivity of the proposed device was found to be 130 nm/RIU which is considered high compared with those reported in the literature. Hence, the proposed structure can be a promising optical device for chemical ultrasensing applications. [ABSTRACT FROM AUTHOR]

In this report, we introduce a 1D photonic crystal (PhC) nanocavity with waveguide-like strain amplifiers within a soft polydimethylsiloxane substrate, presenting it as a potential candidate for highly sensitive pressure and position optical sensors. Due to its substantial optical wavelength response to uniform pressure, laser emission from this nanocavity enables the detection of a minimum applied uniform pressure of 1.6‰ in experiments. Based on this feature, we further studied and elucidated the distinct behaviors in wavelength shifts when applying localized pressure at various positions relative to the PhC nanocavity. In experiments, by mapping wavelength shifts of the PhC nanolaser under localized pressure applied using a micro-tip at different positions, we demonstrate the nanocavity's capability to detect minute position differences, with position-dependent minimum resolutions ranging from tens to hundreds of micrometers. Furthermore, we also propose and validate the feasibility of employing the strain amplifier as an effective waveguide for extracting the sensing signal from the nanocavity. This approach achieves a 64% unidirectional coupling efficiency for leading out the sensing signal to a specific strain amplifier. We believe these findings pave the way for creating a highly sensitive position-sensing module that can accurately identify localized pressure in a planar space. [ABSTRACT FROM AUTHOR]

Refractive index (RI) can be used to identify a particular substance and determine its purity and concentration. The RI of glucose solution with various concentrations can be determined using a distributed Bragg reflective (DBR) device containing a nanocavity. The optical property of the reflection spectrum produced by DBR is sensitive to the variation of the refractive index. In this study, a DBR with a cavity width of 220 nm, located in the middle of the device, is designed and used to sense the variation in the refractive index of glucose at different concentrations. The proposed design showed a sharp dip pattern within the reflection spectrum. The wavelength of the absorption peak was found to be sensitive to trivial variations in the refractive index of glucose solution. Results showed that the variation in the refractive index of glucose within the order of Δn = 0.02 has led to a noticeable shift in the absorption spectrum by Δλ = 2.6 nm. Furthermore, the sensitivity of the proposed device was found to be 130 nm/RIU which is considered high compared with those reported in the literature. Hence, the proposed structure can be a promising optical device for chemical ultrasensing applications.

Gold nanoparticles (AuNPs) integrated within optical fibres show great potential as sensor materials in the field of sensing, utilizing the Surface Plasmon Resonance (SPR) principle. This study presents a straightforward, cost-effective, and replicable approach for producing permanent in-situ embedding of AuNPs with nanocavities on the surface of optical fibres. The process involves chemical vapour etching (CVE), followed by gold sputtering and isothermal heat treatment. The analysis conducted using High-Resolution Transmission Electron Microscopy (HRTEM) and Energy-Dispersive X-ray Spectroscopy (EDX), confirmed the presence of nearly spherical AuNPs embedded on the surface of the optical fibre, with an average diameter of 60 ± 5 nm. Additionally, the detection of two distinct plasmon absorption peaks at 567 ± 5 nm and 620 ± 5 nm using a Fibre Optic Spectrometer further validated the presence of AuNPs. To verify the existence of nanocavities surrounding the AuNPs, Field Emission Transmission Microscopy (FESEM) was employed, along with subjecting the AuNPs embedded fibre to three different NaCl solutions of varying concentrations. The results supported the presence of a nanocavity encapsulating the AuNPs. A proposed mechanism was put forth to explain the spectral behaviour resulting from the creation of the nanocavity. This specialty optical fibre is expected to have broad applications in the development of SPR-based chemicals and biosensors, as it facilitates close interaction between the AuNPs and analytes through the nanocavity surrounding the AuNPs on the fibre surface. The fabrication process demonstrated excellent repeatability, with strong adhesion of AuNPs to the optical fibre surface, and no leaching even after repeated use. Thus, we believe that this fabrication method is an exceptional technique for permanently incorporating AuNPs into various glass-based optical waveguide materials for SPR-based sensing applications. [ABSTRACT FROM AUTHOR]

Polarization-sensitive photodetectors based on two-dimensional (2D) materials have shown more attractive application prospects compared to traditional thin-film photodetectors due to their atomic thickness, tunable bandgap, high mobility and strong light–matter interactions. Among them, 2D molybdenum disulfide (MoS2) has drawn numerous attentions in photodetection due to its wide spectral range, remarkable photoresponsivity and fast photo-switching rate. However, the isotropic crystal structure of MoS2 hampers its application in the polarization-sensitive detection, which is highly desired in military and civilian applications. In this paper, we demonstrated an integration of plasmonic nanocavity with monolayer MoS2 to achieve high photoresponsivity and polarization-sensitive photodetector. With the significant enhancement of electromagnetic field provided by the gap-surface-plasmon (GSP), we achieved a significant photoluminescence (PL) enhancement of 24-fold. Relying on the enhanced light absorption by our plasmonic nanocavity, which generally facilitates photo-generation of electron–hole pairs in MoS2, we achieved a high photoresponsivity of 1.88 A/W and degree of linear polarization (DOLP) of 0.8 at the excitation wavelength of 633 nm. Our work provides a feasible and universal solution to realize polarization-sensitive photodetector of MoS2 for high-performance and polarization-sensitive photodetectors. [ABSTRACT FROM AUTHOR]

In this report, we introduce a 1D photonic crystal (PhC) nanocavity with waveguide-like strain amplifiers within a soft polydimethylsiloxane substrate, presenting it as a potential candidate for highly sensitive pressure and position optical sensors. Due to its substantial optical wavelength response to uniform pressure, laser emission from this nanocavity enables the detection of a minimum applied uniform pressure of 1.6‰ in experiments. Based on this feature, we further studied and elucidated the distinct behaviors in wavelength shifts when applying localized pressure at various positions relative to the PhC nanocavity. In experiments, by mapping wavelength shifts of the PhC nanolaser under localized pressure applied using a micro-tip at different positions, we demonstrate the nanocavity’s capability to detect minute position differences, with position-dependent minimum resolutions ranging from tens to hundreds of micrometers. Furthermore, we also propose and validate the feasibility of employing the strain amplifier as an effective waveguide for extracting the sensing signal from the nanocavity. This approach achieves a 64% unidirectional coupling efficiency for leading out the sensing signal to a specific strain amplifier. We believe these findings pave the way for creating a highly sensitive position-sensing module that can accurately identify localized pressure in a planar space.

Manipulating single emitter radiation is essential for quantum information science. Significant progress has been made in enhancing the radiation efficiency and directivity by coupling quantum emitters with microcavities and plasmonic antennas. However, there has been a great challenge to generate complex radiation patterns such as vortex beam from a single emitter. Here, we report a chiral plasmonic nanocavity, which provides a strong local chiral vacuum field at an exceptional point. We show that a single linear dipole emitter embedded in the nanocavity will radiate to vortex beam via anomalous spontaneous emission with a Purcell enhancement factor up to ∼1000. Our scheme provides a new field manipulation method for chiral quantum optics and vortex lasers at the nanoscale.

The spatiotemporal dynamics of a surface plasmon polariton (SPP) wave packet (WP) that interacts with a plasmonic nanocavity on a metal surface are investigated via femtosecond time-resolved two-photon fluorescence microscopy and numerical calculations. The nanocavity, which consists of a metal–insulator–metal (MIM) laminar structure (longitudinal length: ∼100 nm), behaves as a subwavelength meta-atom possessing discretized eigenenergies. When a chirp-induced femto-second SPP WP is incident on the nanocavity, only the spectral component matching a particular eigenenergy is transmitted to continue propagation on the metal surface. This spectral clipping induces a spatial peak shift in the WP. The shift can be controlled by tuning the eigenenergy or chirp.

3D arrays comprising interconnected voids have been created using nanosphere lithography (2000≤diameter≤240 nm) followed by electrodeposition of gold. The top surface was blocked with 11-mercaptoundecanoic acid and then the templating polystyrenes were dissolved using THF. The interior surfaces were then functionalized with DNA capture strands that are complementary for part of a target sequence associated with methicillin-resistant Staphylococcus aureus, MRSA, genomic DNA. Once the target is hybridised, a probe sequence that is functionalised with [Ru(bpy)2 PIC]2+, is hybridised to the overhang of the target, bpy is 2,2’-bipyridyl and PIC is (2,2′-bipyridyl)-2(4-carboxy phenyl) imidazo [4,5][1,10] phenanthroline. The electrochemiluminescence, ECL, intensity generated from the hybridised ruthenium dye in the presence of tri-propyl amine and normalised for the charge passed depends on the size of the nanocavity. Significantly, the normalised ECL intensity is approximately 7-fold higher for the 820 nm array than either the 2000 nm array or a planar electrode. The array that is functionalised with the capture-target-Ru probe can be used as a 3D bipolar electrode to wirelessly generate ECL. The peak shape and intensity of the wireless ECL spectra depend on the cavity size with the brightest ECL being observed for the 820 nm cavity array. The results are consistent with a fraction of the ECL light activating the broad cavity plasmon of the array and enhancing the overall ECL intensity. The 820 nm array has been used to develop an assay for the detection of MRSA DNA giving a linear dynamic range from 10 nM to 30 µM with an LOD of 1 µM and an LOQ of 3.2 µM. Significantly, the analytical sensitivity of the wireless ECL assay is approximately 7 times higher for the 820 nm array than that observed for a planar electrode.

Graphene plasmons can become the fundamental of novel conceptual photonic devices, resulting from their unique characteristics containing excitation at room temperature and tunable spectral selectivity in different frequencies. The pursuit of efficiently exciting and manipulating graphene plasmons is necessary and significant for high‐performance devices. Here, the graphene plasmon wave propagating in ferroelectric nanocavity array is investigated. It has been experimentally shown that the periodic ferroelectric polarizations can be used for doping graphene into desired spatial carrier density patterns. Based on a theoretical model that considers periodic ununiform conductivity across graphene sheet, the simulation results show surface plasmon polaritons (SPP) in graphene can be excited by an incident light in a similar way to the excitation of photonic crystal resonant modes. The graphene SPP resonance can be tuned from ≈720 to ≈1 000 cm−1 by rescaling the ferroelectric nanocavity array, and from ≈540 to ≈780 cm−1 by dynamically changing the applied gate voltage. This strategy of graphene carrier engineering to excite SPP offers a promising way for large‐scale, nondestructive fabrication of novel graphene photonic devices. [ABSTRACT FROM AUTHOR]

This paper investigates the simulation and performance of Tunnel field effect transistor (TFET) with a nanocavity in it, which can be used for bio sensing application. The entire simulation is done using the tool Silvaco Atlas TCAD. This paper mainly aims in comparing the different parameters for few biomolecules which has different dielectric constant values, namely Streptavidin, Biotin, APTES, Cellulose and DNA. The device structure here consists of a nanocavity near the source end, which is used to place these biomolecules and hence observe the variation of the Drain current v/s Gate voltage characteristic graph, these biomolecules that are having unique dielectric constants are placed within this cavity and these graphs are observed. The energy band diagram of this device is obtained; on top of this various other parameters namely Surface Potential, Electric field are observed for the above-mentioned Biomolecules. The Length of the cavity of the biosensor is also varied to observe the difference, in addition to this Ion (ON current) variation is plotted for the change in the dielectric constant of the biomolecule. [ABSTRACT FROM AUTHOR]

Optical coupling plays a pivotal role in nanophotonic systems, which can be divided into weak, intermediate, and strong‐coupling regimes. Monitoring optical coupling strength is, therefore, the key to understanding light–matter interactions. State‐of‐the‐art approaches based on spectral measurements offer the power to quantify and characterize optical coupling strength at a single cavity level. However, it remains challenging to dynamically characterize coupling strength during the transition from strong‐ to weak‐coupling regimes for many systems simultaneously. Here, a far‐field imaging technique is reported that can directly monitor optical coupling dynamics in plasmon–exciton systems, allowing multiple nanocavity emissions to be characterized from weak‐ to strong‐coupling regimes. Light‐harvesting biomolecules—chlorophyll‐a—is employed to study dynamic light–matter interactions in strongly coupled plasmonic nanocavities. Identification of coupling strength is achieved by extracting red, green, and blue (RGB) values from dark‐field images and an enhancement factor from fluorescence images. Lastly, the ability to monitor subtle changes of coupling dynamics in bioplasmonic nanocavity is demonstrated. These findings may deepen the understanding in light–matter interactions, paving new avenues toward applications in quantum‐based biosensing and imaging. [ABSTRACT FROM AUTHOR]

The fabrication complexity, low sensitivity, detection speed, and costs associated with nanoscale devices have been significant concerns in the development of label-free biosensors. To address these issues, we report a novel dual material control gate cavity on source electrically doped tunnel field-effect transistor (DM-CG-CS-ED-TFET) for label-free biosensors. In this regard, the n + drain and p + source regions within the proposed device are induced by applying polarity gate (PG) bias voltages of PG-1 = +1.2 V and PG-2 = −1.2 V, respectively, across the respective polarity gate electrodes. This approach not only overcomes doping control issues but also avoids thermal budget constraints and minimizes fabrication complexity when compared to conventional TFET. For biomolecule sensing in the device, a nanogap cavity is created within the gate dielectric by selectively etching a portion of the polarity gate dielectric layer towards the source side. The performance of the proposed biosensor device is evaluated based on the variations in carrier concentration profile, energy band diagram, electric field, transfer (I DS - V GS) characteristics, drain current (I DS) sensitivity, ON-state current (I ON) sensitivity, switching ratio (I ON /I OFF) and subthreshold swing (SS) sensitivity. The sensitivity of the device is also investigated based on nano-cavity dimensions, practical challenges such as various filling factors, and the step profile generated from the steric hindrance. Moreover, the effect of temperature on sensitivity has also been investigated. For this, various biomolecules including Streptavidin (k = 2.1), APTES (k = 3.57), ferrocytochrome c (k = 4.7), keratin (k = 8) and Gelatin (k = 12), have been investigated for their performance using Silvaco ATLAS device simulator. The simulation results demonstrate that the proposed biosensor is a viable option for biosensing applications in biomedical engineering. • The electrical performance of dual material control gate cavity on source electrically doped TFET biosensor for biomedical application has been analyzed for both neutral and charged biomolecules. • The impact of cavity thickness, cavity length, non-ideal issues such as fill factor, and different step profiles: decreasing, increasing, concave, and convex on the device performance has been analyzed. • The drain current sensitivity, Ion/Ioff sensitivity, threshold voltage sensitivity, subthreshold sensitivity, sensitivity related to nanocavity regions, and temperature sensitivity have been analyzed. • For faster switching and sensing speed, the transit time performance parameter of the proposed biosensor has also been analyzed. [ABSTRACT FROM AUTHOR]

We present one of the simplest nanoscale systems for a high-performance refractive index (RI) sensor. We investigate analytically and numerically the transmission response of the system, which consists of the rectangular nanocavity coupled to metal–insulator–metal (MIM) nanowaveguide according to its structural parameter and resonance mode of the cavity. From the theoretical results, we find that a square cavity is able to support a hybrid resonant mode of two resonance modes with the opposite symmetry to each other. By comparison with single modes, the hybrid mode enables us to obtain ultra-low transmission response with high quality factor through the system at the resonance and it gives us possibility for realization of RI sensor with both high sensitivity and figure of merit (FoM) based on the system. And the simulation results confirm the theoretical analysis. This nanoscale sensor has a sensitivity as high as 1400nm/RIU and a FoM as large as 3000. The suggested sensor can be widely used as a high-sensitive, highly integrated sensor. [ABSTRACT FROM AUTHOR]

Here, we propose an optical bistable device structure with a few layers of graphene oxide integrated in the metal-dielectric-metal based asymmetric nanocavity. Through the light confinement in the nanocavity, the third order nonlinear absorption of graphene oxide can be significantly enhanced, which experimentally delivers low-threshold optical bistability at the visible wavelength of 532 nm with only 267 KW/cm2 intensity. In addition, the switching threshold can be further reduced via increasing the graphene oxide thickness, hence paving a new way for achieving tunable optical bistable devices at visible light frequencies. [ABSTRACT FROM AUTHOR]

Noble-metal-free surface-enhanced Raman scattering (SERS) substrates have attracted great attention for their abundant sources, good signal uniformity, superior biocompatibility, and high chemical stability. However, the lack of controllable synthesis and fabrication of noble-metal-free substrates with high SERS activity impedes their practical applications. Herein, we propose a general strategy to fabricate a series of planar transition-metal nitride (TMN) SERS chips via an ambient temperature sputtering deposition route. For the first time, tungsten nitride (WN) and tantalum nitride (TaN) are used as SERS materials. These planar TMN chips show remarkable Raman enhancement factors (EFs) with ∼ 105 owing to efficient photoinduced charge transfer process between TMN chips and probe molecules. Further, structural engineering of these TMN chips is used to improve their SERS activity. Benefiting from the synergistic effect of charge transfer process and electric field enhancement by constructing a nanocavity structure, the Raman EF of WN nanocavity chips could be greatly improved to ∼ 1.29 × 107, which is an order of magnitude higher than that of planar chips. Moreover, we also design the WN/monolayer MoS2 heterostructure chips. With the increase of surface electron density on the upper WN and more exciton resonance transitions in the heterostructure, a ∼ 1.94 × 107 level EF and a 5 × 10−10 M level detection limit could be achieved. Our results provide important guidance for the structural design of ultrasensitive noble-metal-free SERS chips. [ABSTRACT FROM AUTHOR]

High-index dielectrics have recently been regarded as promising building blocks in nanophotonics owing to optical electric and magnetic Mie resonances. In particular, silicon is gaining great interest as the backbone of modern technology. Here, silicon dimer nanocavities with different sizes of silicon nanospheres were constructed using a probe nanomanipulation method and interacted with a few-layered R6G membrane to investigate the enhancement of electric and magnetic mode coupling. The evidence of the enhancement of fluorescence and slightly prolonged lifetime of R6G indicated the existence of nanocavities. In addition, the simulated electric and magnetic field distributions and decomposed mode of nanocavity were used to analyze the contribution of electric and magnetic modes to the R6G enhanced fluorescence. Such silicon dimer is a flexible nanocavity with electric and magnetic mode enhancement and has promising applications in sensing and all-dielectric metamaterials or nanophotonic devices. [ABSTRACT FROM AUTHOR]

Plasmonic nanoantennas are able to produce extreme enhancements by concentrating electromagnetic fields into sub-wavelength volumes. Recently, one of the most commonly used nanoantennas is the nanoparticle-on-mirror geometry, which allowed for the room temperature strong coupling of a single molecule. Very few studies offer analysis of near-field mode decompositions, and they mainly focus on spherical and/or cylindrically-faceted nanoparticle-on-mirror geometries. Perfectly spherical nanoparticles are not easy to fabricate, with recent publications revealing that a rhombicuboctahedron is a commonly occurring nanoparticle shape – due to the crystalline nature of metallic nanoparticles. In this paper, we perform a quasi-normal mode analysis for the rhombicuboctahedron-on-mirror nanoantenna and map the field distributions of each mode. We examine how the geometry of the cavity defines the near-field distribution and energies of the modes, and we show that in some cases the mode degeneracies break. This has a significant impact on the radiative emission and far-field profile of each mode, which are measured experimentally. Understanding how realistic nanoantenna geometries behave in the near-field and far-field helps us design antennas with specific properties for controlling and sensing quantum emitters in plasmonic systems. [ABSTRACT FROM AUTHOR]

The spin-spin relaxation in connective tissues is simulated using a model in which the tissue is represented by a set of nanocavities containing H2O-D2O liquid. Collagen fibrils in connective tissues form ordered hierarchical long structures of hydrated nano-cavities with characteristic diameter from 1 nm to several tens of nanometers and length of about 100 nm. We consider influence of the restricted Brownian motion of molecules inside a nano-cavity on spin-spin relaxation. The analytical expression for the transverse time T2 for H2O-D2O the liquid in contained a nanocavity was obtained. We show that the angular dependence of the transverse relaxation rate does not depend on the concentration of D2O. The theoretical results could explain the experimentally observed dependence of the degree of deuteration on the relaxation time T2. Accounting the orientation distribution of the nanocavities well agreement with the experimental dependence of the relaxation for articular cartilage on the deuteration degree was obtained. [ABSTRACT FROM AUTHOR]

Using inelastic electron tunneling spectroscopy with the scanning tunneling microscope (STM-IETS) and density functional theory calculations (DFT), we investigated properties of a single H2 molecule trapped in nanocavities with controlled shape and separation between the STM tip and the Au (110) surface. The STM tip not only serves for the purpose of characterization, but also is directly involved in modification of chemical environment of molecule. The bond length of H2 expands in the atop cavity, with a tendency of dissociation when the gap closes, whereas it remains unchanged in the trough cavity. The availability of two substantially different cavities in the same setup allows understanding of H2 adsorption on noble metal surfaces and sets a path for manipulating a single chemical bond by design.

In this article, we have focused on the concept of junction-free transistor to propose and simulate the ultrathin dielectric modulated (DM) bulk-planar junctionless field-effect transistor (BP-JLFET) as a biosensor device. The proposed device is incorporated with a label-free detection of neutral (proteins, enzymes, streptavidin, and APTES) and charged [deoxyribonucleic acid (DNA)] biomolecules in terms of dielectric constant (K) and charge densities (ρ). For the detection of the biomolecules, the nanocavity is formed by etching out the oxide underneath the gate dielectric at source end. The presence/absence of biomolecules has been detected by the factor of sensitivity with the immobilization of dielectric constant (K) and the charge density (ρ) in the formed nanocavity. Moreover, the comparative study of the BP-JLFET, the dielectric-modulated tunnel field-effect transistor (DM-TFET), and the conventional dielectric-modulated field-effect transistor (DM-FET)-based biosensor in terms of their drain current (Ids) and the sensitivity have been carried out. From the study, it can be depicted that the BP-JLFET has higher sensitivity to sense the biomolecules compared to both the DM-TFET and the conventional DM-FET. Furthermore, we have also analyzed the noise characteristics for the simulated structures to measure the ability of the proposed device for sensing the biomolecules in the presence of noise. [ABSTRACT FROM AUTHOR]

• Nanocavity geometry effects on nucleate boiling are first investigated by molecular dynamics simulation. • Bubble dynamics and heat transfer characteristics for different scenarios are systematically compared. • Underlying mechanisms are analyzed and elucidated based on numerous quantitative results. • Combined effects of nanocavity geometry and solid-liquid interaction are identified. • Provide essential guidance towards surface design in thermal energy systems. In recent years, surfaces with nanocavities have been identified to considerably improve boiling heat transfer, that is highly promising for advanced thermal energy systems. To boost developments in nanostructured boiling surfaces, effects of nanocavity geometry on nucleate boiling at the nanoscale are systematically studied for the first time by utilizing molecular dynamics simulation. Three typical nanocavities with rectangular, semicircular, and triangular cross-sectional shapes are constructed, which have the identical width and depth (8 nm and 4 nm). Moreover, three representative wetting conditions corresponding to different solid-liquid interaction strengths are further considered to provide a comprehensive understanding of geometry effects. The results manifest that nanocavity geometry effect on nucleate boiling can be attributed to the differences in their solid-liquid contact area and solid-liquid interactions play a vital role in reinforcement effectiveness. When the solid-liquid interaction is sufficiently strong (energy coefficient equals 1.5, termed ultra-superhydrophilicity), variations in nanocavity geometries will induce remarkable effects on boiling performance. Among three geometric configurations, the rectangular nanocavity exhibits the highest heat transfer efficiency and achieves maximum boiling enhancement, including significant improvements in bubble nucleation and growth, as well as critical heat flux. This study provides an essential insight into nanoscale boiling reinforcement mechanism. [Display omitted] [ABSTRACT FROM AUTHOR]

Intragranular nanocavities were observed in the Cr 2 O 3 layer of a Cr 3 C 2 +Cr coated Zirlo™ specimen corroded in steam at 1200 ℃ for 1 h. By comparing the coated specimen that was quenched from 1200 ℃ with the one that was not, we considered the root cause of the intragranular nanocavities in Cr 2 O 3 was that the nanocavities that formed in the original coating were trapped into the Cr 2 O 3 grains during the corrosion process. This explanation may also apply to the formation of intragranular nanocavities in single metal Cr-coated zirconium alloys corroded at high temperatures. [ABSTRACT FROM AUTHOR]

High-index dielectrics have recently been regarded as promising building blocks in nanophotonics owing to optical electric and magnetic Mie resonances. In particular, silicon is gaining great interest as the backbone of modern technology. Here, silicon dimer nanocavities with different sizes of silicon nanospheres were constructed using a probe nanomanipulation method and interacted with a few-layered R6G membrane to investigate the enhancement of electric and magnetic mode coupling. The evidence of the enhancement of fluorescence and slightly prolonged lifetime of R6G indicated the existence of nanocavities. In addition, the simulated electric and magnetic field distributions and decomposed mode of nanocavity were used to analyze the contribution of electric and magnetic modes to the R6G enhanced fluorescence. Such silicon dimer is a flexible nanocavity with electric and magnetic mode enhancement and has promising applications in sensing and all-dielectric metamaterials or nanophotonic devices.

The dielectrically modulated heterostructure TFET based nanocavity embedded label-free biosensors are emerging as low power, highly sensitive bio-analyte detectors. High sensitivity and fast detection of biomolecules are still a challenge for researchers. In this article, single cavity dual-material extended gate heterostructure (III-V) TFET (SC-DM-EG HTFET) based dielectrically modulated label-free biosensor is proposed; which promises higher sensitivity and better device performances such as, ON current, $\text{I}_{ON}/\text{I}_{OFF}$ ratio, subthreshold swing (SS); compared with single cavity dual-material heterostructure TFET (SC-DM HTFET), dual cavity dual-material heterostructure TFET (DC-DM HTFET), as well as, previously proposed FET based biosensors. 2D numerical simulation of the biosensors was performed with SILVACO ATLAS 2D simulation software. III-V heterostructure (InGaAs/Si) and extended gate geometry provide increased tunneling probability, improved gate control, high $\text{I}_{ON}/\text{I}_{OFF}$ ratio, and ultra-high sensitivity, compared to IV-IV heterostructure biosensors. The sensitivities of the biosensors are analyzed for both neutral and charged biomolecules, with dielectric constants $\text{K}=5$ ,7,10,12. Effect of non-ideal issues on sensitivity, such as temperature fluctuation, steric hindrance are also studied for the biosensors mentioned above. Benchmarking is done to provide a quantitative comparison of the proposed biosensor with published literature. A maximum sensitivity of $1.3\times 10^{8}$ , along with the $\text{I}_{ON}/\text{I}_{OFF}$ ratio of $2\times 10^{12}$ and SS of 25.4 mV/V is noticed in SC-DM-EG HTFET for the dielectric constant of $\text{K}=12$ in a completely filled cavity of neutral biomolecules. [ABSTRACT FROM AUTHOR]

In this paper, 2 D hexagonal photonic nano crystal cavity is structured and simulated after infiltrating hemoglobin and urine samples for refractive index biosensing application. The proposed sensor accompanies hexagonal cluster of dielectric rods whose radius is 240 nm and at lattice constant of 800 nm respectively. The refractive index of bio-samples is taken for different concentrations and because of connection among light and analyte, a shift in the resonant wavelength is observed. Simulation results reports generously proportioned shifting of resonant wavelength and elevated sensitivities for biosensor. Photonic band gap is determined by PWE method and simulation results have been investigated using OptiFDTD. [ABSTRACT FROM AUTHOR]

Here, we propose an optical bistable device structure with a few layers of graphene oxide integrated in the metal-dielectric-metal based asymmetric nanocavity. Through the light confinement in the nanocavity, the third order nonlinear absorption of graphene oxide can be significantly enhanced, which experimentally delivers low-threshold optical bistability at the visible wavelength of 532 nm with only 267 KW/cm2 intensity. In addition, the switching threshold can be further reduced via increasing the graphene oxide thickness, hence paving a new way for achieving tunable optical bistable devices at visible light frequencies.

In this report, we propose an idea of connecting 1D photonic crystal (PhC) nanocavity with novel waveguide-like strain shapers in a polydimethylsiloxane substrate. In theory, the induced film-edge strain by the strain shapers can significantly enhance the wavelength tunability of PhC nanocavity under different applied stress. By our nanofabrication process, we realize this idea in the form of a tunable nanolaser. In experiments, the nanolaser shows the enhanced wavelength tunability both under stretching and compressive stress. By investigating the effects of PhC periods and length of the strain shapers, we obtain an optimized lasing wavelength tunability of −13.9 nm under every percentage strain variation in experiments. When further taking the 2nd-order mode in the nanocavity into consideration, we observe a wide lasing wavelength tuning range over 160 nm, which takes only the applied strain Δ ξtot of ±0.05. In addition to the large wavelength response beneficial for tunable nanolasers and optical strain sensors, we also believe that this waveguide-like strain shapers can serve as the optical interconnections at the same time in the flexible photonic circuits. [ABSTRACT FROM AUTHOR]