In recent past, high-repetition-rate, ultrafast pulse excitation has been identified to play an important role in stable trapping of dielectric nanoparticles assisted by optical nonlinearity due to its high peak power. We experimentally demonstrate trapping of 100-nm fluorescent polystyrene particles by simultaneous detection of both two-photon fluorescence (TPF) and backscattered signals. Here we show that TPF signal decays over time due to photobleaching, but this signal is useful to know whether a particle is dragged toward the trap while backscattered signal provides detailed information about the particle’s dynamics inside the trap. We also discuss pros and cons of moving-averaging method (used to smooth noisy experimental data). We conclude that both TPF and backscattered detection methods are needed to explore the dynamics of the particle inside the potential well.

Gold and silver nanoparticles attract broad scientific interest for their applications in chemical and biological sensing and imaging and for their potential in biomedical therapeutics. Pulse laser ablation in liquids has been extensively used as a clean alternative to chemical methods for the production of metal nanoparticles. Hence, the major aim of related research is to produce highly stable colloidal nanoparticles with finer nanoparticles and a narrower size distribution. The purpose is to compare the ability of various liquid media (ethanol, distilled water, and acetone) to reproduce the spectra and size distribution of gold and silver nanoparticles formed using the laser ablation technique. The analysis is conducted through the ultraviolet–visible–near infrared absorbance spectroscopy and transmission electron microscopy images. Gold and silver nanoparticles that are synthesized in acetone display high spectral stability compared with that of the nanoparticles synthesized in distilled water and ethanol; this difference is mainly due to the ability of acetone to synthesize particles with a much smaller size and narrower particle size distribution.

Nanostructure color filters filter light spectrum via the structural engineering, unlike traditional dye filters that rely on the chemical compositions to absorb light. In light of the successful advance in micro/nanofabrication technology in the past decades, these structured color filters are particularly promising for future applications in ultrascaled color filtering and multispectral imaging. We will summarize the recent progress in nanostructure color filters based on plasmonics, nanowires, metamaterials, and quantum dots (QDs). Plasmonics filters rely on surface plasmon resonances to realize the spectrum selection. For nanowire color filters, the color filtering is achieved by light coupling into the leaky or waveguiding mode in nanowires. In metamaterial filters, the refractive index of artificial materials is manipulated to create a broad color palette. QDs color filters rely on bandgap engineering to create filtering effects by simply altering the size and composition of the QDs. Clearly, the above filtering technologies have their own pros and cons, which will be analyzed.

We report on the effect of temperature on the differential gain, differential refractive index, and linewidth enhancement factor (α-factor) of ∼1610-nm chirped barrier thickness multistack InAs quantum-dash (Qdash)-in-a-well laser diodes with an extended active region inhomogeneity. By employing Hakki–Paoli method, the performance is found to be comparable at a lower temperature region (16°C to 25°C), exhibiting higher differential gain and lower α-factor values of ∼0.7  ±  0.1  cm^−  1 mA^−  1 and ∼2.6  ±  1.0, respectively, at gain maximum. At higher temperatures of 25°C to 35°C, the performance degrades mainly due to drop of the differential gain at a rate of ∼0.03  cm^−  1 mA^−  1  °  C^−  1 and α-factor values reaching ∼4.7  ±  2.0 at 40°C. The room temperature (20°C) measured values are in good agreement with the literature, and we qualitatively explain the temperature influence on these results from the highly inhomogeneous Qdash system viewpoint. This study will assist in further optimization of these nanostructure-based high active region gain laser devices that are promising candidates in L-band optical communications, capable of providing low-frequency chirp and high-performance operation.

We propose a kind of magnetic photonic crystal (MPC) slab waveguide made from magneto-optical material, namely bismuth iron garnet. The finite difference beam propagation method is employed for numerical calculations, which is the most widely used propagation technique for modeling integrated and photonic devices. The mode conversion and the influence of corresponding parameters are studied theoretically. As a numerical example, a TE-TM mode conversion waveguide-type optical isolator based on this designed MPC is described. An effective away to enhance the Faraday rotation at the 1.55-μm telecommunication wavelength is shown.

We have investigated the channel length dependence of the key performance parameters, such as speed, responsivity, external quantum efficiency (EQE), and responsivity–bandwidth product, of the silicon carbide nanowire-based ultraviolet (UV) photodetector devices with different channel lengths ranging from 120 to 800 nm. The device with the shortest channel length of 120 nm at low bias voltage of 0.5 V exhibited very high responsivity and EQE of 7.73  ×  10³  A  /  W and 7.77  ×  10⁴  %  , respectively, under illumination to 254-nm UV light. Our experiments revealed that reduction in channel length resulted in significant enhancement in speed, responsivity, EQE, and responsivity–bandwidth product of the photodetector. This study suggests that scaling down in channel length could enable the development of high-speed and sensitive photodetector devices for emerging nanophotonic and nanoelectronic applications capable of operating at low voltages.

While long-range propagating plasmons have been extensively investigated for implementing on-chip optical sensing platforms, waveguide-excited localized surface plasmon resonance-based sensing systems have not yet received much attention. Waveguide excitation and readout, an alternative to free-space single-particle spectroscopy, are particularly attractive. A numerical investigation of the optical response of a waveguide-excited plasmonic dolmen-shaped compound nanoantenna is presented. The dolmen shape is found to offer improved refractive index sensing performance in comparison to simpler shapes for both spectral-shift and intensity-shift measuring modalities. The compound plasmonic nanoantenna configuration presented is of interest in hybrid photonic-plasmonic sensing approaches with high-throughput capabilities.

We compared 9  ×  9 arrays of bimetallic Ni(Nickel)-Pt(Platinum) nanoantennas for a classic and evolutive dipole configuration. We fabricated the nanoantennas by e-beam lithography and characterized them with a solar simulator to analyze the I  −  V curves. From these curves, a thermoelectric voltage dependence associated by classic and evolutive dipole configuration was observed. We show that the evolutive dipole nanoantennas (EDN) generate up to three times more voltage in contrast with the classic dipole nanoantenna (CDN). Indeed, the evolutive configuration is 1.3 times more efficient than its classical counterpart. The results are corroborated by absorbance of these nanoantennas in the 20 to 36 THz range, where EDN is 40% more efficient than CDN and 30% in the range of 36.1 to 90 THz. Moreover, the experimental results match the thermoelectric behavior obtained using numerical simulations. The EDN can be used in applications ranging from aerospace technology to energy harvesting, photodetector, and sensors, where high thermoelectric efficiency is needed.

A subwavelength interference nanolithography scheme is numerically demonstrated based on a metallic–insulator–metallic waveguide combined with unidirectional couplers. The coupler is a single right-angled (or left-angled) trapezoid metallic nanoslit that can carry out efficient unidirectional generation of surface plasmon polaritons under normal incidence. Simulation results show that a feature size to 50 nm half-pitch uniformity pattern can be obtained at the working wavelength of 365 nm with the proposed scheme. This proposed scheme can enhance the intensity of the interference pattern with higher contrast and field depth and is advantageous for the fabrication process in practical applications.

Enhancing electrical conductance in organic semiconductors has been a focus of intense research over the last few decades. The improvement can be made by optimizing either the material or the device architecture. As it has been shown by Orgiu et al., strong coupling of organic molecules with a nanostructured plasmonic substrate can significantly improve the molecules’ electrical conductivity. We searched for the effect of strong coupling with a Fabry–Perot cavity on the conductivity of the semiconducting poly(3 hexylthiophene-2, 5-diyl) (P3HT) polymer. Despite the observation of the strong coupling evidenced by a very large Rabi splitting of 1.0 eV, the increase of electrical conductivity with increase of the P3HT film thickness was primarily affected by an increase of the polymer’s order in thick P3HT films.

A chiral plasmonic lens (CPL) suitable for circularly polarized light is proposed; it consists of multiple concentric grooves surrounded by two Archimedes-spiral distributed arrays of rectangular nanoslits milled into a gold film. We demonstrate both theoretically and numerically that the proposed CPL can convert an incident circular polarization beam with prescribed chirality into a long centrosymmetric focus with a size beyond the diffraction limit, but the circularly polarized one with the opposite chirality cannot be transmitted and focused by the same CPL due to the chirality of the proposed structure. Depending on the design parameters, an optical needle or optical tube in the focal field can be achieved; the attainable focus has a full-width at half-maximum of 0.43λ₀ and an elongated depth of focus of 2.95λ₀ with λ₀ denoting the wavelength of illumination light.

A structure is suggested for spasing. The presented surface plasmon amplification by stimulated emission of Radiation (SPASER) is made up of a graphene nanosphere, which supports localized surface plasmon modes, and a quantum dot array, acting as a gain medium. The gain medium is pumped by an external light source. Since all the plasmons are carried on a graphene platform, the structure features coherent surface plasmons with high confinement and large life time. All the structures are analyzed theoretically using full quantum mechanical description. The main advantage of the proposed SPASER is its simple tuning capability of changing graphene’s Fermi level, which is performed by either chemical doping in the manufacturing time or electrostatic gating. We suggest the utilization of the proposed SPASER for exciting coherent long-range surface plasmons on a graphene sheet. The near field of the SPASER couples to the surface plasmons on graphene sheet and compensates the large momentum mismatch between surface plasmons and photons.

A plasmonic perfect absorber (PPA) based on a metal–insulator–metal–insulator–metal structure has been designed for refractive index sensing of glucose solutions (analyte). Then resistor–inductor–capacitor equivalent circuit models based on dimensions, the position of the components, and materials used in the structure have been developed to predict resonance frequencies of the absorber. Simulation results show that in the perpendicular incidence of a plane wave of light within 5 to 9  μm wavelengths, for the analyte placed over sensor surface with a refractive index of n  =  1.312; the output absorption spectrum of the device has two resonance peaks, respectively, on λ₁  =  6441.01  nm and λ₂  =  7909.74  nm wavelengths. When the refractive index of analyte increases to n  =  1.384, both resonant peaks are red shifted. Sensitivities (S  =  Δλ  /  Δn) of the first and second resonance peaks have been obtained as S₁  =  1287.083  nm  /  RIU and S₂  =  1142.5  nm  /  RIU, respectively.

The solid-core photonic crystal fiber (PCF) sensor with circular sensing ring has been proposed for biochemical detection. Finite-element method-based numerical technique has been applied to solve Maxwell’s equations with perfect matched boundary conditions. The relative sensitivity and confinement losses are two performance parameters of PCF sensor for blood component detection. In the proposed design, the circular sensing ring over solid core is filled with different blood components and light propagates inside the core region. The evanescent field of core mode uniformly interacts with sensing liquids. The sensing ring is preferred over the multiple air holes because of easy liquid infiltration and fabricated for biosensing applications.

A tunable metamaterial absorber based on hybrid structure design strategy is suggested and numerically verified. An absorption peak (82.5%, at resonance wavelength 1.52  μm) is achieved at room temperature without Fermi energy, which is derived from local surface plasma (LSP) modes excited on edges of metal particles. The adjustability of this structure is derived from two structural components: vanadium dioxide (VO₂) particles are temperature sensitive and graphene films are sensitive to Fermi energy and Fermi energy difference. Therefore, the resonant properties of this structure can be modulated by varying the temperature, energy, or energy difference. Simulated results reveal that two new absorption peaks are achieved at the resonance wavelengths 1.82 and 2.09  μm, which are both derived from the LSP modes excited on edges of VO₂ particles. Moreover, both new absorption peaks are enhanced with the simulated temperature increased. Three optimized values of the carrier mobility μ are achieved: VO₂ particles support region 8200  cm²  /    (  V  ·  s  )  , metal particle support region 8800  cm²  /    (  V  ·  s  )  , and suspended region 230,000  cm²  /    (  V  ·  s  )  . The absorption peak is enhanced and shifted to shorter wavelength with the Fermi energy level increasing, while the absorption peak is reduced and shifted to longer wavelength with the Fermi energy difference reducing.

An emission illusion device based on metamaterials with the cylindrical polar angle-dependent tensors of permittivity and permeability was proposed and analyzed. The illusion effect was numerically simulated using the finite-element method for a point source. The influence of metamaterial anisotropy and radiation source position on the illusion effect was studied.

A simulation and analysis of a ring resonator-based sensor are presented. The ring resonator structure has two bus waveguides and two rings with a gap between the ring and the ring and bus waveguide. The radius of each ring is designed to be 3.1  μm. The ring resonator is designed such that both rings exhibit resonance at 1550 nm, and it is analyzed at mid-infrared wavelengths between 1500 and 1600 nm. The guided signal is launched through the bus waveguide to determine spectral properties, such as free spectral range and quality (Q-) factor. An improved Q-factor is observed in the simulation results for the optimized design. The improved Q-factor allows us to analyze the ring resonator for use in sensing applications.

The binding energy and diamagnetic susceptibility of shallow hydrogenic impurity in cylindrical quantum dot is calculated using a variational approach within the effective mass approximation, as a function of dot size when the static pressure and the magnetic field are applied simultaneously. We describe the quantum confinement by an infinite deep potential; the numerical calculations are performed for HgS, which is a narrow gap, and GaAs, a large gap semiconductor. The results show that the diamagnetic susceptibility increases with the reduction in dot sizes and decreases when the hydrostatic pressure increases. We have shown that diamagnetic susceptibility strongly depends on size of the nanostructure and decreases with increasing size of the quantum dot and tends toward the limit of the bulk (−1, 1 a.u.) (increase in diamagnetic susceptibility in absolute value). We have found that the displacement of the impurity from the center of the quantum dot to the edge causes a decrease in the diamagnetic susceptibility. The absolute value of diamagnetic susceptibility of donors in GaAs is lower than in HgS.

A Y-junction of low-difference refractive-index (RI) and coupler as its input was designed and simulated. The simulation uses COMSOL Multi-Physics Software Package, allowing varying crucial parameters. A detailed analysis and optimization of the device for single-mode design was made, in order to achieve a maximum input area error while preserving a good 50-50 splitting ratio. This approach of combined design and simulations of special Y-junction can benefit and predict advanced optical communication.