A gap plasmon is an electromagnetic wave propagating in a gap between two noble metal surfaces. Such gap plasmons have previously been studied using only a classical description of the noble metals, but this model fails and shows unphysical behavior for sub-nanometer gaps. To overcome this problem quantum spill-out is included in this paper by applying Density-Functional Theory (DFT), such that the electron density is smooth across the interfaces between metal and air. The mode index of a gap plasmon propagating in the gap between the two metal surfaces is calculated from the smooth electron density, and in the limit of vanishing gap width the mode index is found to converge properly to the refractive index of bulk metal. When neglecting quantum spill out in this limit the mode index shows unphysical behavior and diverges instead. The mode index is applied to calculate the reflectance of an ultrasharp groove array in silver, as gaps of a few nm are found in the bottom of such grooves. At these positions the gap plasmon field is highly delocalized implying that it mostly exists in the bulk silver region where absorption takes place. Surprisingly, when the bottom width is a few nm and the effect of spill out at a first glance seems to be negligible, strong absorption is found to take place 1-2 Å from the groove walls as a consequence of the dielectric function being almost zero at these positions. Hence quantum spill out is found to significantly lower the reflectance of such groove arrays in silver.

Epsilon-near-zero materials are ideal platforms for nonlinear optics. Extreme electric field enhancements are predicted when a transverse-magnetic polarized field impinges obliquely on a film of material whose real part of the dielectric permittivity approaches zero. Under these circumstances, the component of the electric field with polarization normal to the film surface is enhanced by a factor proportional to the inverse square root of the dielectric permittivity. Nonlinear processes benefit from such uniquely favorable field localization, whether the condition is achieved in natural or artificial materials. Nonlinear optical processes have also been shown to be affected by the interference mechanism that occurs when two counter-propagating beams/pulses interact. Counter-propagating pulse dynamics has been investigated for surface plasmons and guided beams, they have been used for direct characterization of ultra-short pulses, to control emission of high-harmonics and to indirectly measure the phase mismatch of waveguides. Finally, they have been studied also in one dimensional photonic crystals and negative index materials. However, all these examples rely on either phase-matching or the availability of photonic resonances. Here we demonstrate that, thanks to the ability of epsilon-near-zero materials to efficiently support nonlinear processes in the absence of phase-matching or resonant conditions, one can control harmonic generation process by altering the phase of two non-collinear counter-propagating beams. We investigate the dynamics of two non-collinear counter-propagating beams impinging on an epsilon-near-zero slab and evaluate the modulation of the second and third harmonic signals as a function of the phase difference between the two sources. The calculations are performed considering a 100nm-thick slab of indium-tin-oxide (ITO). The results confirm that epsilon-near-zero media are exceptional platforms for nonlinear optics, providing a novel path to control these processes, including the possibility to easily characterize optical pulses.

Nanoparticles exhibit various optical properties arising from scattering and absorption due to polariton excitation. The resulting frequency and amplitude is dependent on several factors such as particle size, shape, and dielectric environment. By modifying the environment of the nanoparticle surface, in particular by encapsulating an individual nanoparticle within a membrane bilayer comprising defined phospholipids, these properties may be utilised to interrogate molecular interactions adjacent to the particle surface to useful levels of sensitivity. We describe the underlying rationale of these properties and characterise the preparation and behaviour of the nanoparticles. We indicate the potential this approach may have for sensing and screening in analytical biomolecular technology by demonstrating that it can be utilised to reveal the kinetics of the molecular interactions of membrane associated events. We also indicate that the technique may yield higherorder structural information of the macromolecule-membrane interactions in a highly sensitive manner and discuss the physical origins of these potentially more exotic phenomena.

The development of planar functional junction provides continuous, single-atom thick, in-plane integrated circuits. The production of atomic contacts of different materials (hetero/homostructures) is still a challenging task for 2D materials technology. In this paper we describe a new method of formation of a photosensitive junction by femtosecond laser pulses patterning of graphene FET. The laser-induced oxidation of graphene goes under high intensity laser pulses, which provide nonlinear effects in graphene like multiphoton absorption and hot carrier generation. The process of laser induced local oxidation is studied on single-layer graphene FET produced by wet transfer of CVD grown graphene on copper foil onto a Si/SiO₂ substrate. The 280 fs laser with 515 nm wavelength with various pulse energies is applied to modify of local electrical and optical properties of graphene. Thus, the developed process provides mask-less laser induced in-plane junction patterning in graphene. The scale of local heterojunction fabrication is about 1 μm. We observe that with an increasing of the laser fluence the number of defects increases according to two different mechanism for low and high fluences, respectively. The change of the charge carrier concentration causes the Dirac point shift in produced structures. We investigate the photoresponse in graphene junctions under fs pulsed laser irradiation with subthreshold energies. The response time is rather high while relaxation time is large because of charge traps at the graphene/SiO₂ interface.

We propose octagonal quasi-crystal designs providing effective light confinement for different resonance frequencies through the structural modification with the utilization of low-symmetric photonic unit cells. The effect of rotational symmetry reduction on the cavity resonance appearing in the corresponding photonic bandgap of each structure has been investigated. Relatively small dielectric cylinders have been additionally located at discrete angular positions with particular distances from the center of the each core cylinder and the noteworthy resonance peaks have been observed to emerge in the bandgaps. Rotational symmetry of the proposed structures is to be modified by varying the angular displacement of the smaller quasi-crystalline rods with the angle θ in terms of the x-axis of the small rod. The successful demonstration of tunable resonance modes has been achieved numerically and experimentally for the first time by tailoring the positional parameters and reducing the crystalline symmetry. Strongly localized modes in the proposed quasi-crystals have great potential for various slow light applications along with other technologies such as sensors, lasers and memory units.

A three dimensional rigid spherical microscopic object can rotate in either the pitch, yaw or roll fashion. Among these, yaw motion has been conventionally studied using the intensity of the scattered light from birefringent microspheres through crossed polarizers. So far, however, there is no way to study the pitch rotational motion in spherical microspheres. Here we suggest a new method towards the study of such pitch motion in birefringent microspheres under crossed polarizers by measuring the 2-fold asymmetry in the scattered signal using video microscopy. We show a simple example of pitch rotation determination using video microscopy for a microsphere attached with a kinesin molecule while moving along a microtubule. It can also be extended to optical tweezers.

We propose and demonstrate experimentally an optical analogue of the famous Archimedes' screw where airborne particles are conveyed down or upstream the photons momentum ow through the rotation of a helical optical beam. We also report on the action of such a rotating screw on low-absorbing particles in a solution.

We report on the optical properties of recently developed telecom-wavelength quantum dots based on the GaAs material system. In order to achieve the InAs quantum dot wavelength shift towards the telecom C-band, strain-relaxation with the help of an InGaAs metamorphic buffer is realized. The general emission properties of the quantum dot ensemble and single dots is analyzed, containing analysis of lifetime measurements and fine-structure splitting investigations. Single-photon emission is verified for excitation in continuous wave and pulsed mode. The generation of polarization-entangled photon pairs via the biexciton-exciton radiative cascade is shown, even for increasing time windows and time delays.

Polarized time resolved fluorescence measurements are used to characterise the structure of the two-photon tensor in the enhanced green fluorescent protein (EGFP) and predict the “hidden” degree of hexadecapole transition dipole alignment 〈α₄₀〉 created by two-photon absorption (TPA). We employ a new method for the accurate STED measurement of the evolution of 〈α₄₀〉 by analysing the saturation dynamics of the orthogonally polarized components of two-photon excited EGFP fluorescence as a function of the time delay between the 800 nm pump and 570 nm dump pulses. The relaxation of 〈α₄₀〉 by homo-FRET is found to be considerably greater than that for the fluorescence anisotropy which directly measures the quadrupolar transition dipole moment alignment 〈α₂₀〉. Our results indicate that higher order dipole moment correlation measurements promise to be a sensitive probe of resonance energy transfer dynamics.

Semiconductor quantum dots (QDs) are a promising “nano-antennas” capable of absorbing efficiently light energy upon one- or two-photon excitation and then transferring it to convenient energy acceptors via Förster resonance energy transfer (FRET). The photosensitive protein bacteriorhodopsin (bR) has been shown to be a promising material for optoelectronic and photovoltaic applications, but it cannot effectively absorb light in the UV, blue, and NIR regions. It was shown previously that formation of hybrid complexes of QDs and purple membranes (PMs) containing bR could significantly improve the bR capacity for utilizing light upon one- and two-photon laser excitations. Under the laser irradiation, the optical properties of bR itself remain unchanged, whereas those of QDs may be altered. Therefore, it is important to study the effects of intense laser excitation on the properties of the QD–PM hybrid material. In this study we have shown that laser irradiation can lead to an increase in the luminescence quantum yield (QY) of QDs. The fact that this irradiation does not change the QD absorption spectra means that the QD quantum yield may be optically controlled without changing the QD structure or composition. Finally, we have shown experimentally that photoinduced increase in the QY of QDs lead to the corresponding increase in the efficiency of FRET in the QD–PM hybrid material. As a result, an approach to increasing the FRET efficiency in hybrid nano-biomaterials where QDs serve as donors have been proposed.

The issue of whether the optical orbital angular momentum of light can play any significant role in chiroptical interactions has seen a resurgence of interest in the past few years. Revising preliminary expectations, it has been shown both theoretically and experimentally that the topological charge can indeed play a decisive role in some chiroptical interactions, with the rates of these optical phenomena proving sensitive to the sign of the vortex charge ℓ. Using quantum electrodynamics, it is now revealed how the inclusion of molecular electric-quadrupole transition moments in both chiral and achiral anisotropic media produces such an effect. Specifically, for single-photon absorption it transpires that both the orbital and spin angular momentum must be engaged through a circularly polarized vortex beam. The chiroptical effect is identified as a manifestation spin-orbit interaction in light.

The capacity to tailor as wanted the fluorescence’s properties of a fluorophore increases the number of applications were the same fluorophore can be useful, like in imageology. One way to modify these properties is the presence of plasmonic fields nearby the fluorophore, and their origin can be the surface plasmons generated in metallic nanoparticles, like silver and gold, when these are excited. Usually fluorescence quantum yield is studied by conventional fluorescence spectroscopy techniques, but these are subjected to errors from reflection or refraction from the sample and a way to avoid these errors is to use indirect measurements techniques as in the case of thermal lens spectroscopy, which measures the change generated by the sample’s absorption of radiation, instead of measuring the absorption per se as regular spectroscopic methods. This technique is based in the photoinduced refraction index’s change. In this work we studied the effect that silver nanoparticles had in the fluorescence’s properties of ethanolic solutions of rhodamine B, specially its quantum yield, using a mode-mismatched thermal lens setup. We found that the presence of silver nanoparticles lowers the dye’s quantum yield between 4% and 38% which depends on the dye and nanoparticles’ concentrations. The thermal diffusivity’s values showed that the silver nanoparticles are increasing the non-radiant decay velocity of the rhodamine b, which is the reason why the quantum yield gets lower. These results not only gave us information about the studied samples, but also validate the capacity of a mode-mismatched thermal lens system to study fluorescence properties.

The molecular clusters, so called J-aggregates of pseudoisocyanine dye, were obtained in ordered cylindrical nanopores of anodic aluminum oxide. The absorption and luminescence of the samples were studied by the VIS-spectroscopy and laser confocal microscopy. The band of J-aggregates has the same shape, but is inhomogeneous broadened in comparison with solution. The luminescence maximum of J-aggregates was observed at 578 nm upon excitation at 543 nm as well as at 405 nm. Non-resonant luminescence excitation occurred due to energy transfer from oxygen vacancy of alumina to molecular nanoclusters. This is also confirmed by time-resolved luminescence spectroscopy, which shows the increase of luminescence decay time of J-aggregates placed in alumina up to the luminescence time of the clean alumina in comparison with J-aggregates coated on glass substrate.

We propose and demonstrate photonic crystals (PCs) providing backward-directional propagation of surface slow waves, which is significant for potential PC-based photonic applications. An effective pathway for backward directing of surface slow light along with the modification of other important characteristics is presented via implementing surface morphological diversity in PCs. With the surface orientation angle varying from 900 to 300, the newly appearing bands inside the band gap shift to higher frequencies, and negative group indices up to -100 are observed as the strong indication of backward propagation. Furthermore, dependence of the propagation direction on the surface corrugation angle has been verified via detailed time-domain analyses and microwave experiments using dipole source. As obtained from both the numerical and experimental results, for instance, the structure with 600 provides a well-defined backward propagation. In addition, normalized-delay-bandwidth-product can easily be modified by varying the surface orientation angle in the proposed structures according to the necessities of the application. Furthermore, the group velocity dispersion spectra extracted for each periodic structure exhibit considerably high-range near-zero values as 0.139 ps²/m at 900 for the range of 495.54-501.25 nm and 0.176 ps²/m at 85° for the range of 495.66-501.25 nm. Third order dispersion spectra also obtained for the proposed PCs show near-zero values as 0.098 ps³/m at 900 and 0.113 ps³/m at 85° in the corresponding frequency regimes. Facile control of the key characteristics such as backward-directed surface wave propagation in the periodic dielectric structures having morphological diversity serves a great potential for nextgeneration photonic applications.

In this work, we perform numerical studies of two photonic crystal membrane microcavities, a short line-defect L5 cavity with relatively low quality (Q) factor and a longer L9 cavity with high Q. We compute the cavity Q factor and the resonance wavelength λ of the fundamental M1 mode in the two structures using five state-of- the-art computational methods. We study the convergence and the associated numerical uncertainty of Q and λ with respect to the relevant computational parameters for each method. Convergence is not obtained for all the methods, indicating that some are more suitable than others for analyzing photonic crystal line defect cavities.

In this paper, we study the use of Titanium Nitride (TiN) as a new alternative plasmonic material to achieve a highly sensitive surface plasmon resonance (SPR) photonic crystal fiber (PCF) biosensor. The TiN has unique properties that make it an ideal material for nanofabrication, where TiN is highly stable, highly conductive, and corrosion resistant. Full vectorial finite element method is used with perfectly matched layer (PML) as boundary conditions to analyze the suggested biosensor. By analyzing the geometrical parameters of the proposed biosensor, a refractive index sensitivity of 7700 nm/RIU and 3600 nm/RIU are obtained for quasi-transverse electric (TE) and quasi transverse magnetic (TM) modes, respectively. The reported biosensor has a high linearity for detecting an unknown analyte refractive index ranging from 1.32 to 1.34. Further, fabrication of the proposed biosensor could be done using standard PCF fabrication current technologies.

We propose a novel approach in optical trapping exploiting mesoscopic photonic crystal microcavities. Full light confinement in mesoscopic photonic crystal membranes, forming a mesoscopic self-collimating 1D Fabry-Pérot cavity, was theoretically predicted and experimentally verified by the authors in previous papers. In this paper, we numerically demonstrate a high performance MPhC microcavity for optical trapping of fine particulate matter in air. The MPhC cavity has been simulated by 3D FDTD simulations while the trapping potential has been evaluated by means of the gradient force density convolution method. We numerically show that it is possible to obtain very high trapping potential for polystyrene particles having radii as small as 245 nm.

A modified nanocone nanowire (NW) is proposed and analyzed for solar cell applications. The suggested NW consists of conical and truncated conical units. The geometrical parameters are studied by using 3D finite difference time domain (FDTD) method to achieve broadband absorption through the reported design and maximize its ultimate efficiency. The analyzed parameters are absorption spectra, ultimate efficiency and short circuit current density. The numerical results prove that the proposed structure is superior compared to cone, truncated cone and cylindrical nanowires (NWs). The reported design achieves an ultimate efficiency of 44.21% with an enhancement of 40.66% relative to the conventional conical NWs. Further, short circuit current density of 36.17 mA/cm² is achieved by the suggested NW. The modified nanocone has advantages of broadband absorption enhancement, low cost and fabrication feasibility.

There is currently significant interest in operating devices in the quantum regime, where their behaviour cannot be explained through classical mechanics. Quantum states, including entangled states, are fragile and easily disturbed by excessive thermal noise. Here we address the question of whether it is possible to create non-reciprocal devices that encourage the flow of thermal noise towards or away from a particular quantum device in a network. Our work makes use of the cascaded systems formalism to answer this question in the affirmative, showing how a three-port device can be used as an effective thermal transistor, and illustrates how this formalism maps onto an experimentally-realisable optomechanical system. Our results pave the way to more resilient quantum devices and to the use of thermal noise as a resource.

Strong coupling between excitons and light leads to the formation of hybrid states with mixed properties of light and matter. As a result, interesting physical phenomena have been observed at room temperature, e.g. Bose–Einstein condensation and superfluidity, and novel applications are emerging, such as low threshold lasers and quantum devices. Recently it was shown that metasurfaces of aluminum nanoantennas coated with molecular J-aggregates can provide an excellent platform for the formation of strongly coupled exciton-localized surface plasmons (X-LSPs). However, their optical nonlinearities and temporal dynamics are still not well understood. In this work, we use femtosecond pump-probe spectroscopy to study X-LSPs in such composite Al/molecular metasurfaces on time scales that are longer than their Rabi oscillation period. We study the linear and nonlinear optical properties of the uncoupled and hybrid systems and find that the nanoscale plasmonic confinement in metallic nanoparticle cavities introduces intriguing new ultrafast phenomena in the strong coupling regime. These include modifications of the hybrid system due to femtosecond changes in the molecular environment, picosecond oscillations due to acoustic breathing modes of the nanoantennas, and long relaxation times of the nonlinear perturbation at the upper X-LSPs frequency band.

Geometric Spin Hall effect of light (SHEL) has attracted considerable attention because of the universality of this variant of the spin Hall shift and its independence on the light-matter interactions and materials properties. However, the magnitude of geometric SHEL is typically very small, in the sub-wavelength domain, making it difficult for direct experimental observation. Here, we have applied weak measurement schemes to amplify and faithfully observe the geometric SHEL. In our experiment, the input beam is pre-selected in linear polarization basis (p- or slinear polarization) and post selections are done at nearly orthogonal linear polarizations (small angle ϵ away from the exact orthogonal).This results in weak value amplification (~cotϵ) of the resulting shift of the beam centroid. Moreover, this process also leads to selective conversion of spatial to angular nature of geometric SHEL, which along with the weak value amplification leads to manifold amplification of the resulting SHEL, enabling its reliable experimental detection. A key feature of our weak measurement scheme is that both the weak perturbation (tiny geometric SHEL) and the post selection are done simultaneously by a single optical element, namely, a linear polarizer. The dependence of the weak value of the geometric SHEL on the pre and the post selection of polarization states in both linear and elliptical basis were also investigated in details. The specifics of the different weak measurement schemes, various intriguing experimental manifestations of the weak value amplified geometric SHEL, their analysis / interpretation via polarization operator based treatment of weak measurements is presented here.

The combination of nonlinear and integrated photonics enables applications in telecommunication, metrology, spectroscopy, and quantum information science. Pioneer works in silicon-on-insulator (SOI) has shown huge potentials of integrated nonlinear photonics. However, silicon suffers two-photon absorption (TPA) in the telecom wavelengths around 1550 nm, which hampers its practical applications. To get a superior nonlinear performance, an ideal integrated waveguide platform should combine a high material nonlinearity, low material absorption (linear and nonlinear), a strong light confinement, and a mature fabrication technology. Aluminum gallium arsenide (AlGaAs) was identified as a promising candidate for nonlinear applications since 1994. It offers a large transparency window, a high refractive index (n≈3.3), a nonlinear index (n2) on the order of 10^-17 m2W⁻¹, and the ability to engineer the material bandgap to mitigate TPA. In spite of the high intrinsic nonlinearity, conventional deep-etched AlGaAs waveguides exhibit low effective nonlinearity due to the vertical low-index contrast. To take full advantage of the high intrinsic linear and nonlinear index of AlGaAs material, we reconstructed the conventional AlGaAs waveguide into a high index contrast layout that has been realized in the AlGaAs-on-insulator (AlGaAsOI) platform. We have demonstrated low loss waveguides with an ultra-high nonlinear coefficient and high Q microresonators in such a platform. Owing to the high confinement waveguide layout and state-of-the-art nanolithography techniques, the dispersion properties of the AlGaAsOI waveguide can be tailored efficiently and accurately by altering the waveguide shape or dimension, which enables various applications in signal processing and generation, which will be reviewed in this paper.

In our work, we employ the resonant electromagnetic properties of III-V semiconductor nanowires to design building blocks for nonlinear all-dielectric metamaterials and devices. Contrary to widely used Si and Ge nanostructures, III-V materials, such as GaAs or AlGaAs, have a direct band gap and non-centrosymmetric crystal structure, which makes them promising for the development of nonlinear metamaterials. We developed an innovative approach to fabricate disk and rod nanoantennas by slicing bottom-up grown nanowires using a focused ion beam milling (FIB). The proposed method allows to significantly decrease the influence of the substrate on the electromagnetic field distribution inside the nanoantenna and it opens the possibility to use any substrate regardless of the nanostructure fabrication process. With this technique, we study the influence of geometry, design and crystal structure on the characteristics of all-dielectric nanoantennas. It offers unique opportunities to fabricate high-quality structures with variable radii, longitudinal heterostructures with lattice-mismatched materials, and structures with different refractive indexes and crystal phases that are not available in bulk materials.

This paper focus on the theoretical investigation of quantum confined Stark effect (QCSE) in strain compensated SiGeSn/GeSn single quantum well (QW). Eigen energies in presence of electric field, for Г valley conduction band (Г- CB) and heavy hole band (HH)) are obtained from the self consistent solution of coupled Schrödinger and Poisson equations by finite difference method. Absorption coefficient considering excitonic effect for direct transition of HH band to Г valley is calculated. A significant shift in absorption peak towards longer wavelengths is observed.

Several coherent light sources with dimensions less than the diffraction limit were proposed and demonstrated in the last decade. One of the most popular of them is a spaser. Since its theoretical proposal, there were a number of experimental realizations based on metal nanoparticle colloids and laser dyes. However, the disaffection with these realizations grows as the conditions of the performed experiments were too close to that of the random-lasing phenomena. Hence, an experiment with a refined setup that greatly reduces an unintended feedback due to the multiple scattering events is in order. In this work, we achieved this goal by creating a monolayer of metal nanoparticles on the solid surface and cover them with a thin layer of dye molecules.

The identification of threshold in nanolasers still poses not entirely met challenges. Dynamical techniques offer interesting methods to determine the achievement of coherent emission. A recent experimental proposal rests on the dynamical shift of a bifurcation in the presence of a modulated pump indirectly observed through the study of the behaviour of the zero–delay second–order autocorrelation function of the detected photon number. This paper investigates the potential for directly observing the dynamical hysteresis which accompanies the sweep across threshold in a large β nanolaser. We conclude that the observation is possible in principle, but that the experiment has to be carefully designed to achieve this goal.

Multiply resonant silicon photonic devices based on three coupled nanobeam cavities are proposed engineer third order nonlinearities at wavelengths around λ=1.55μm. We show that varying the geometrical parameters allows a flexible tuning of linear properties of the system, especially the deviations between the cavity resonance wavelengths. Based on the linear regime results, the nonlinear properties of the system are studied using coupled mode expressions of the supermodes given by the Tight-Binding method for the calculation of the nonlinear integrals controlling the intensity of the third-order nonlinear effects of the photonic molecules. We geometrically control the self-phase modulation (SPM), the cross-phase modulation (XPM), and the degenerate four-wave mixing (DFWM) nonlinear coefficients of the three coupled nanobeam cavities and identify general trends for nonlinear applications such as optical switching and frequency conversion devices.

Being restricted to the domain of validity of spherical wave expansions, the T-matrix method has been in question to model light scattering by nonspherical particle systems when inter-particle distances are low. In this work, we discuss a formalism to account for multiple scattering between nonspherical particles in close vicinity. Accurate coupling between adjacent particles’ scattered fields is achieved by an alternative plane-wave formulation of the translation operator for spherical vector wave functions. The accuracy of the presented approach is demonstrated by a far field simulation of a large particle cluster. The near field of nonspherical particles has not been accessible in T-matrix simulations thus far. Utilizing the benefits of plane-wave expansions, the near field of nonspherical particles can be constructed in T-matrix simulations. We hereby show that the T-matrix method is also applicable for the analysis of localized resonances, making it suitable for the description of plasmonic systems.

The stochastic implementation of the laser rate equations is discussed in detail, in light of its application to numerically predict the properties of nanolasers. The deterministic integration scheme is analysed and tested for appropriateness to the problem. The simplest stochastic, first-order scheme is considered and its particular properties and requirements are discussed. Tests for the correctness of the numerical integration are presented. Finally, thorough tests for the convergence of the stochastic integration are performed, showing their different aspects and possible pitfalls.

In this paper, new design of Yagi-Uda nano-antenna (NA) based on ellipsoid shape is introduced and numerically analyzed using 3-D finite difference time domain method (3-D FDTD) via Lumerical software package. The NA parameters are optimized using the particle swarm optimization (PSO) algorithm to achieve high directivity at a wavelength of 500 nm for wireless point-to-point applications. To illustrate the performance of the proposed antenna, different radiation parameters such as radiation pattern, directivity, and radiation efficiency have been studied. The optimized ellipsoid nano-antenna shows a directivity of 22.36 which is enhanced by 86.3 % relative to the conventional spherical counterpart. Moreover, the fabrication tolerance of the reported design is studied to ensure the accuracy of the introduced NA parameters to the fabrications errors.

In order to detect DNA hybridization with label free and high sensitivity, a hybrid alternative plasmonic slot waveguide (HAPSW) biosensor based on silicon-on-insulator (SOI) is proposed and analyzed. The reported design increases the light interaction with the sensing region by using a slot-waveguide along with titanium nitride as an alternative plasmonic material. The suggested biosensor can detect the slightest change in the analyte refractive index with high sensitivity due to an ultra-high optical confinement in the low-index regions caused by the high index contrast and plasmonic enhancement. The effective index, normalized power confinement, and sensitivity are analyzed for the detection of the DNA hybridization. The simulation results are obtained using full vectorial finite element method (FVFEM). The suggested biosensor has high sensitivity of 1190 nm/RIU (refractive index unit) for DNA hybridization detection, which is very high relative to those reported in the literature to the best of our knowledge.

A novel design of multiplexer-demultiplexer (MUX-DEMUX) based on channel waveguide on silicon dioxide (SiO₂) is introduced and analyzed. The suggested structure consists of two neighboring channels infiltrated with nematic liquid crystal (NLC) material of type E7. The two channels are etched in the SiO₂ substrate. The electro-optic effect of the NLC is used to control the waveguide propagation condition using an external electric field. Additionally, a plasmonic wire is inserted between the two waveguides to enhance the suggested MUX-DEMUX in terms of compactness. The modal analysis of the y-polarized modes supported by the NLC MUX-DEMUX is carried out using full-vectorial finitedifference method (FVFDM). Further, the propagation characteristics through the reported design are obtained using full vectorial finite difference beam propagation method (FVFD-BPM). The design parameters of the NLC MUX-DEMUX have been studied to obtain an efficient waveguide coupling with a short device length. Moreover, the NLC MUXDEMUX has a compact device length of 1296 μm. The numerical results reveal that the reported MUX-DEMUX has a small insertion loss of 8x10^-6 dB with a good crosstalk better than -37 dB and -30 dB at the studied wavelengths of 1.3 μm and 1.55 μm, respectively. To the best of the authors’ knowledge, it is the first time to introduce a MUX-DEMUX based on channel on SiO² platform with a simple design and broadband operation.

We exhibit a structure built with inorganic and organic material nanostructure arrays. The zinc oxide (ZnO) nanorods were synthesized by hydrothermal method and could be the precursor model to build our nanostructure. The as-fabricated ZnO nanorods were then surrounded with the inorganic material, lead telluride (PbTe). It could be filled with the organic material, Poly Methyl Methacrylate (PMMA), in the hexagonal hole after the ZnO nanorods were removed by simple chemical aqueous etching process. Finally, we can obtain an organic/PbTe array matrix nanostructure.The thermoelectric properties of as-fabricated device were measured and temperature dependence of physical mechanism for organic and inorganic hybrid nanostructure was discussed.

Plasmonic quasicrystals stand out as the center of cynosure behind the many potential applications which emerges due to the quasi-periodic structure and metal dielectric patterns. The rotational symmetry elicits the optical properties resembling like crystals and and the metal dielectric nanostructure are being probed and explored in various disciplines of science and even in engineering also. Plasmonic quasicrystals composed of quasi- periodic and metal-dielectric patterns furnish efficacious benefits in improving the efficiency of solar cells, broadband transmission enhancement, and bio-sensing applications etc. Due to the intriguing properties of plasmonic crystals such as periodicity and short range ordering, the excitation of the surface Plasmon polaritons is restricted by a few fewer techniques such as polarization, launch angle dependence. Polarization contains wealth of information and holds the potential to control the interaction of light with metal Nano particles. Therefore, an exhaustive and thorough information regarding incident and scattered light is necessary for the examining the spectral response of the quasi crystal. Here, we report to the best of our knowledge the first ever quantitative polarimetric studies on the extremely complex plasmonic quasicrystal by recording a full 4x4 spectral Mueller matrix from the same and tried to explore the fascinating and interesting properties of quasi crystals. A homebuilt comprehensive Mueller Matrix platform (integrated with dark field microscope) is utilized to record the conventionally weak, intermixed polarization signal from plasmonic quasicrystals. These studies probed the enthralling phenomena of Fano resonance, explored and probed the presence of phase anisotropy in the plasmonic quasicrystals using the Mueller matrix derived retardance (δ) parameter. Additionally polarization mediated tuning of Fano Resonance is achieved too. Moreover it is demonstrated that the Mueller matrix derived diattenuation, retardance parameters probes the Fano resonance, phase and amplitude anisotropy from such complex plasmonic nanostructure and proved instrumental in polarization controlled tuning of Fano resonance.

In this study, the absorption capabilities of a plasmonic funnel-shaped silicon nanowire (SiNW) solar cell is introduced and analyzed by using 3D finite difference time domain method (FDTD). The reported NW design has titanium nitride (TiN) core as an alternative plasmonic material. The different geometrical parameters of the reported design are studied to maximize the absorption and hence the ultimate efficiency. An ultimate efficiency and short-circuit current density J_sc of 48.3% and 38.98 mA/cm², respectively are obtained which are greater than the conventional Si-Funnel counterpart by 46.36%. The enhancement of the light absorption is attributed to the combination between different types of optical modes and plasmonics modes of the funnel-shaped NW and the TiN, respectively.

In this paper by the methods of Raman spectroscopy, a drop of the evaporating liquid of Human Serum Albumin with the Rhodamine 6G dye molecules in the presence of silver nanoparticles obtained by laser femtosecond ablation in water was studied. In the Raman spectra, an increase in the intensity of scattering of dye molecules with silver nanoparticles the addition of protein molecules was recorded. We suppose that the observed effect is associated with the diffusion and thermal processes in the drop arising during laser excitation.

A hexagonal shape surface plasmon photonic crystal fiber (PCF) biosensor is reported and studied numerically. The proposed design has three identical cores along the y-axis filled with liquid (analyte). Additionally, the central core is coated by a gold layer to facilitate the coupling among the plasmonic modes and the core fundamental modes. A full vectorial finite element method is used to analyze the proposed sensor with a perfectly matched layer boundary condition. Further, the particle swarm optimization (PSO) technique is used to optimize and improve the sensitivity of the presented sensor as well as reduce the sensor’s size. Through the optimization process, the diameters of the three cores, and the thicknesses of the gold layer are fluctuated. For a wavelength range 1.46-1.47, the sensitivity of the proposed sensor is 4000 nm/RIU.

As performance and power consumption of modern micro-chips are increasingly limited by electrical on-chip interconnects, all-optical interconnect systems promise data transmission at speed of light and wavelength- division multiplexing. To realize complex networks, active devices, like lasers, need to be integrated on Si. III-Vs are excellent candidates for optical devices, however, their integration on Si is challenging due to a significant lattice and thermal mismatch. Template-assisted selective epitaxy (TASE) was recently developed by our group, allowing for the selective growth of III-Vs from a small Si seed in a confined oxide template. In this work, we extend TASE towards optical devices and demonstrate the monolithic integration of InGaAs lasers via a novel approach using a virtual substrate (VS) in a two-step templated growth. First, μm² sized 60 nm thick InGaAs VSs are grown by MOCVD using TASE on SOI. Subsequently, 500 nm oxide are deposited onto the VS and patterned in arbitrary shapes like disks, and rings. In a second InGaAs growth, the defined vertical cavities are filled. The investigated structures have diameters of 1.7 μm, thicknesses of 0.5 µm and total cavity volumes of 0.5 λ³₀. Photoluminescence spectroscopy reveals a broad spontaneous emission peak around 1.1 μm (FWHM = 150 nm) that increases linearly with pump power for low excitation powers (<< 2.6 pJ/pulse). Above excitation threshold, a strong emission peak emerges at 1.1 μm (FWHM = 7 nm). The Input-Output curve (log- log, T = 10 K) exhibits the characteristic S-shape which constitutes a strong indication for the lasing operation. The onset of the lasing threshold is observed up to 200 K with a characteristic temperature of T₀ = 192 K.

We show that scattering of plane waves leads to helicity-independent transverse spin angular momentum (SAM) and helicity-dependent transverse Poynting vector components. The in uence of plasmon resonance and avoided crossing for a sphere on these quantities is studied.

We demonstrate the realization of desired gold plasmonic nanostructures by direct laser writing (DLW) method employing a continuous-wave 532 nm laser. By moving the laser focusing spot of the DLW system, the gold nanoparticles (NPs) are formed following the laser moving path. The plasmonic patterns composing of gold NPs enable a lot of applications, such as direct text writing and inverse text writing at micro scale, bar code and QR code to store the messages, binary recordings as compared to standard CDs and DVDs. Furthermore, by controlling the laser intensity and/or the exposure time, the NPs size was changed resulting in different plasmonic colors, and offering a new method to nanoprint with color.

The optical processes of plasmonic enhancement of rhodamine 6G molecules fluorescence in dielectric films of polyvinyl alcohol deposited on a rough silver surface have been studied. The reflection coefficients of the polarized light components on rough silver surfaces have been determined by means of spectral ellipsometry and spectrophotometry methods. Two kinds of silver surfaces were used: without and with anodizing at current density of 5 mA/cm² of 0.5 μm layer. The plasmon spectrum appeared to be red-shifted after polyvinyl film deposition onto the silver plate. I was shown that the silver-dielectric interface roughness affects the position of the reflected light spectrum maximum to 360 – 400 nm range due to the dielectric polarizing effect.

The article explores the influence of plasma energy of ytterbium nanoparticles on the fluorescent and absorption characteristics of the porphyrin molecules (Ethioporphyrin) in methylcellulose films. There has been ascertained the presence of plasmon energy transfer in the porphyrin-cluster system of the ytterbium nanoparticle at the wavelengths of fluorescence registration. The values of the increase in percentage proportion were defined. It was demonstrated that with the clusters concentration increasing the optical density of porphyrin molecules and fluorescence intensity increases.

We investigate the optical properties of nanogap MIM nanoantennas with a 2.1 nm thick gap. These plasmonic nanoantennas consist of a gold film, an insulating layer deposited by Atomic Layer Deposition, and a periodically structured gold layer. MIM nanoantennas are characterized by a tunable spectral response and a high field confinement within the nanogap. Nanometric gaps enable high coupling between the plasmons of the top and bottom metal surfaces. We demonstrated an excellent agreement between optical measurements and classical electromagnetic simulations. In particular, we observed a fluctuation in the gap thickness of 0.2 nm.

A method for preparation silver nanoparticles supporting plasmon oscillations is proposed. Using a seed-mediated growth approach in a rod-like micellar media, silver nanorods of varied aspect ratio were prepared from nearly spherical silver nanoparticles. The concentrations of synthesis reagents were determined to obtain nanorods whose plasmon resonances are shifted toward larger wavelengths relative to resonances of spherical particles.

Coupling of a single photon source into photonic structures is highly demanded for implementation of numerous applications in quantum information processing and quantum dot (QD)-based solid-state platforms. In this work, we present a simple strategy for coupling a single semiconductor colloidal nanocrystal (NC) into polymer-based photonic structures. By utilizing low one-photon absorption (LOPA) direct laser writing (DLW) technique, we demonstrate the precise patterning of 2D SU-8 microstructures containing an individual core/shell CdSe/CdS NC. Various shapes of desired structures are fabricated with a single embedded NC while keeping its photon antibunching property as a single photon source. These results open a wide range of perspectives in term of quantum information, tunable emission, and efficient light harvesting by using polymer-based photonic crystal.

We studied the influence of the ligands on the optical properties of PbS QD solids using the photoluminescence spectra and the kinetics of photoluminescence decay. As the ligand molecule length decreases, the photoluminescence decay becomes faster, which in a good agreement with the theory of the hopping mechanism of charge transfer in QD solids. We also fabricate photovoltaic structures (ITO/PEDOT:PSS/PbS/ZnO/Al) based on PbS QD solids and investigate the influence of various organic ligand molecules on its photovoltaic characteristics. The maximum efficiency was observed in samples with a ligand of intermediate length.

Using an optical pump and a time delayed white light super continuum probe, delay dependent switching is achieved between saturation absorption (SA) and reverse saturation absorption (RSA) above a threshold pump intensity in reduced graphene oxide (RGO2). RGO2 is obtained using photo-thermal reduction and chemical reduction respectively. The wavelength regime which experience switching can be varied by changing the degree of reduction. At 415 nm pump, the threshold intensity to obtain switching property decreases to 9 GW/cm² for RGO2 from 18 GW/cm² in graphene oxide(GO) and the tunability range shifts from 471-526 nm for as grown GO to 519-623 nm in maximally reduced RGO2.Though the saturation intensity of intrinsic non-degenerate two photon absorption (nd-TPA) is found to be lower in GO (4.3 GW/cm²) than RGO2 (18.2 GW/cm²), nd-TPA coefficient increases from 0.0015 cm/GW (GO) to 0.0026 cm/GW (RGO2) with increasing reduction. Decay dynamics of scattering processes show faster relaxation of electron in RGO than in GO. Results are accounted using a model band diagram based on amorphous-carbon model.

We propose a horizontally symmetrical three-layer dielectric structure composed of a high-index central (core) layer surrounded by two identical low-index cladding layers, which acts as an optical differentiator in reflection. If the refractive index of the surrounding medium is greater that the refractive index of the cladding layers, the spectra of the considered structure may exhibit resonant features associated with the excitation of a leaky mode localized at the central layer. At resonant conditions, the reflection coefficient will vanish at certain values of frequency and angle of incidence, which enables the differentiation of the incident optical pulse. We theoretically justify that this three-layer structure can perform temporal differentiation (differentiation of an incident optical pulse envelope), spatial differentiation (differentiation of an optical beam profile) and the so-called “spatiotemporal differentiation” (differentiation of an optical signal envelope along a certain direction in the (x,t)-plane). Rigorous numerical simulation results demonstrate high quality of differentiation. It is shown that the resonance quality factor increases with the increase in the thickness of the cladding layers, which makes it possible to achieve a required linearity interval of the differentiating filter. The proposed differentiator is more compact than Fourier correlators containing graded-index lenses and substantially easier to fabricate than metasurface-based devices incorporating periodically arranged nanoresonators and may find application in ultrafast analogue computing and signal processing systems.

Here, we present the design and fabrication details of a metal grating-one dimensional photonic crystal (1DPhC) structure that can efficiently couple the normal incident light into the 1DPhCs. We implement this by designing a silver (Ag) nano-grating on the 1DPhC which consists of 10 bilayers of SiO2/TiO2 thin films on a silicon substrate. Ag coated 1DPhC shows a sharp dip in the reflectivity within the photonic stop band, which is a distinct signature of the excitation of Tamm states at the interface of metal-1DPhC boundary. Reflection spectrum of Ag grating–1DPhC structure shows that the Tamm state is modified in the presence of the Ag grating, giving rise to a surface state in the vicinity of the Tamm resonance. The experimental results obtained are well supported by simulations which provide the field distributions for the Tamm resonance and the surface state.

Fluorescent nanomaterials such as metal nanoclusters (NCs) have become one of the most essential nanomaterial and attracted abundant attention in research due to their excellent photophysical properties and wide range of applications. Furthermore, metal nanoclusters have been predominantly investigated owing to its excellent optical properties, simple synthetic routes,low toxicity and excellent photostability. However, limited advancements and progress have been executed in fabricating hydrophilic and highly luminescent metal NCs. Copper is an eco-friendly, low-cost metal which is progressively advancing into focus for metal NCs research. In comparison to the extensively studied gold nanoclusters (Au NCs) and silver nanoclusters (Ag NCs), systematic and analytical applications of the copper nanoclusters (Cu NCs) are relatively limited and still at an early stage. In this review, we fixate on contemporary advances in the analytical applications of Cu NCs based on their behavior and properties of light. This work specifically addresses optical properties and some emerging applications of Cu NCs. The study seeks to unravel some unique photophysical properties of Cu NCs in its solid state, namely concentration/aggregation induced emission enhancement, thermally activated delayed fluorescence (TADF), by which both singlet and triplet excitons can be harvested. Furthermore, the as-synthesized Cu NCs used in this study was remarkably excellent, garnering ~20% quantum yield in colloidal and solid-state form, respectively. CuNC/PVA nano-composites can exhibit unique solidstate- induced dual-mode emissions of thermally activated delayed fluorescence (TADF) and phosphorescence at ambient environment. The outstanding performance of Cu NCs in solid-state makes it an excellent biocompatible nanoemitters light-emitting devices.

Plasmonic nanocircuits have the potential to open up new routes in manipulating optical information beyond the diffraction limit and future quantum information processing technologies. We present on-chip polarization conversion based on interaction between two interfering surface plasmon modes supported by metal-insulator-metal (MIM) waveguides. The functional device is realized by all-plasmonic Mach-Zehnder Interferometers (MZI) equipped with impedance-matched Yagi-Uda style nanoantennas for highly efficient far-field coupling. By controlling the relative phase difference between guided MIM gap plasmons propagating in a MZI, namely by precisely differentiating the individual path length, a rotation of the mode optical axes is observed. Depending on the phase difference the resulting mode at the junction point, where two branching channels merge into one channel, can be symmetric or antisymmetric. Accordingly, two cases are investigated in ultra-compact (< 40 μm²) high-definition circuits, where the antisymmetric and symmetric mode are distinguished by observing the origin position and the polarization of the scattering signals. A high conversion efficiency can be realized, encouraging potential application in functional plasmonic nanocircuits.

The optical properties of organometallic films of silver nanoparticles and J-aggregates of pseudoisocyanine dye have been studied to observation of the plasmon-exciton interaction. The original method for obtaining J-aggregates on inhomogeneous island silver films without use of salt and water was developed. Owing to the broad bandwidth of inhomogeneous plasmon resonances; it is possible to study the interaction of nanoparticles and J-aggregates, obtained in the spin-coated layer on the silver island film. The absorption spectrum of the organometallic film is not a simple sum of the spectra composing its components. The absorption of dye molecules increases several times in the presence of silver nanoparticles, which is due to the influence of the near fields of the latter. The spectral dip in the absorption maximum of the J-aggregate of pseudoisocyanine was observed; it became more symmetrical with an increasing equivalent thickness of the island film.

In this study, we have investigated the potential of bimetallic hollow nanostructures (BHNS) consisting of silver and gold metals for the detection of mercury in an aqueous medium. The BHNS of varying compositions of gold and silver were prepared by galvanic etching of the template silver nanoparticles (AgNPs) using gold(III) salt solution. The BHNS of varying composition were prepared by modulating the molar ratio, of gold to silver, ranging from 0.13 to 2.0, in the reaction mixture. The resultant nanostructures were characterized using UV-Vis spectroscopy and transmission electron microscopy. The absorption maxima of the BHNS batches were found to be increased from 463 ± 9 nm to 611 ± 12 nm as a function of gold to silver molar ratio. An increase in the nanoparticles size was observed from 54 ± 6 (molar ratio = 0.25) to 75 ± 10 (molar ratio = 2.0) with an increase in gold to silver molar ratio. The interaction of different volumes of mercury solution (ranging from 0.1 to 0.4 mL) with all types of BHNS was studied. A considerable change in color of the solution was observed and consequently, a change in the absorbance intensity and a shift in the peak plasmonic wavelength was also noticed. Among the different BHNS batches investigated, the highest change in the intensity and peak wavelength was observed for BHNS0.13, with higher silver and lower gold content. This suggests that the reaction between silver and mercury is more favored compared to that between mercury and gold.