This PDF file contains the front matter associated with SPIE Proceedings Volume 12322, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Photopolymerization induced by up conversion nanoparticles (UCNPs) are reported to have promising potential in the biological and nano-imaging field. Here, a novel method of nanoscale writing at low power level is demonstrated through the incorporation of UCNPs under a two-beam far-field direct laser writing (DLW) configuration. Equipped with long lifetime of excited energy levels, UCNPs were employed to function as the excitation light source for inducing controlled reversible deactivation radical polymerization through activating polymerization photo reagents via resonance energy transfer in the localized area surrounding the UCNPs, hence generating polymerized micro-scale features upon an incident near-infrared laser beam.

UCNPs with unique emission qualities were custom-synthesized and dispersed in a monomer-based mixture containing polymerization photo-reagents to formulate a photo-sensitive nanocomposite. A thin film sample based off the nanocomposite was then placed under a two-beam super-resolution writing scheme for the fabrication of 3D micro-structures at low power level (100sW/cm2 for the writing laser beam intensity).

Able to generate 3D nanoscale-features at low power level with unique photo-luminescent properties in comparison with the traditional two-photon writing, this new nanoscale writing technique possesses significant application potential in fields of nanophotonics such as 3D micro-prototyping, 3D low-power nanoscale optical data storage, nanoscale-resolution imaging and functional nanoscale-photonic devices.

In recent years, there has been tremendous development in photonic integrated circuits (PICs) because of the growing demand for computational power and the slowing down of transistor shrinkage. PICs are seen as a promising technology for developing next-generation technologies including the Internet of Things, on-chip data routers, and optical quantum computers due to their compatibility with the long-established complementary metal-oxide-semiconductor fabrication technology and making use of common materials such as silicon and silicon dioxide. As the size of the PICs is shrinking and considering different aspects such as modal size mismatch, fabrication/packaging cost, it has become increasingly difficult to couple light efficiently in-plane or out-of-plane among different photonic elements such as waveguides and fibers. In this study, we propose a two-layer grating coupler using a horizontally placed angle-polished single-mode optical fiber. We used the finite-difference time-domain method and optimization tools including the inverse design technique to investigate the design parameters for performance enhancement of light coupling in silicon-on-insulator (SOI) integrated circuits. We achieved a coupling efficiency of -1.54 dB (70.15%) for fiber-to-SOI chip coupling and a coupling efficiency of -0.97 dB (80%) for chip-to-fiber coupling over a wide bandwidth.

We study whispering gallery modes circulating at the surface of bent optical fibers. Investigate the spectra the effective radius variations for modes with different quantum numbers, we found that modes with different radial and azimuthal numbers experience the same effective radius variations within the experimental precision (∼ 100MHz), in contrast to modes with different polarizations, that are altered with bending differently.

With the rapid development of portable equipment, the demand for the miniaturization of optical elements is increasing. Metasurfaces are considered as potential planar analogs of conventional devices due to their small size and their extraordinary ability to modulate light. As one of the most important branches of metasurfaces, metalenses attract much attention and are fascinating to develop compact, miniature optical imaging devices. However, the highly chromatic characteristic limits their further applications. Therefore, achromatic metalenses with constant focal lengths over a broad bandwidth are highly desirable. Here, we demonstrate a diffraction-limited achromatic metalens with an octave-wide bandwidth in the infrared. Unlike typical metalenses with periodic unit cells, the proposed metalens comprises well-designed an aperiodic array of elements based on the Pancharatnam-Berry phase. The proposed metalens with a numerical aperture of 0.49 achieves an average focusing efficiency of 37% in a wavelength range from 1.15 to 2.3 μm, which is one octave, and maintains a near-constant focal length of 25 μm. It paves the way for miniaturized and broadband imaging applications.

Terahertz (THz) band has been attracting an enormous reputation due to the paucity of natural materials in this range. Artificially flat thin films, called metasurfaces, plead the research community owing to their unprecedented features to manipulate the scattering properties of electromagnetic (EM) waves. Capitalizing on these unique attributes of the metasurfaces, a wideband polarization converter is investigated for THz frequencies. The proposed metasurface rotates the incoming EM wave into its cross-component over a broad spectral range from 1 THz to 1.75 THz. The designed polarization conversion metasurface (PCM) manifests above 90% efficiency, having a bandwidth of 0.75 THz. This unit cell is also scalable to other operating regimes such as microwave and visible, just by scaling its physical dimensions. This kind of wideband PCM remains prudent for various applications of radar cross-section reduction (RCSR), imaging, communication, etc.

Over the past few years, Deep-learning (DL) based modelling solutions have been presented as an alternate to the timetedious and computationally draining conventional design and optimization procedure of metasurfaces. While designing a phase-based transmission meta-device, such as meta-lenses and meta-holograms etc., the most crucial part is to optimize its unit-cell to ensure maximum electromagnetic (EM) transmission amplitude and full phase coverage (0-2π). Most of the DL-based solutions have resulted in accurate optimization to provide the desired transmission amplitude. But the abrupt discontinuities in the phase response, makes it more challenging to map and predict the optimized structure for full phase coverage. Here, we present a novel DL-based tool named as “Meta-Magus” to design transmission based metaholograms. Meta-Magus consists of two parts: (i) unit-cell optimization, and (ii) phase mask generation. Here, the first component takes target transmission amplitude, phase, material properties, and the wavelength aimed as input, process it via regression based tandem neural network, and provide optimized unit-cell structural parameters as output. Target image whose hologram is to be generated is fed to the second component which comprises of deep convolutional neural network to generate the corresponding phase mask as output. A full-wave commercial simulator then maps the optimized unit-cell onto the generated phase mask and generates the intended meta-hologram. Simulation results of the generated designs exhibit perfect holography, and validates that the model yields excellent predictions of a complete metasurface design from scratch within a matter of seconds.

Manipulating electromagnetic waves by controlling their amplitude, phase, and polarization is essential for implementing numerous exciting applications and consumer-level devices. However, conventional optical elements acquire phase accumulation through the propagation effect, which results in bulky optical devices and thus hinders their further miniaturization. In recent years, the remarkable development of nanofabrication technologies enabled the emergence of artificially engineered ultrathin structures called metasurfaces that provide a fascinating boulevard to tailor the field distribution of electromagnetic waves at the micron scale. Metasurfaces are ultrathin optical components with an array of low-loss, precisely engineered building blocks that exhibit the unprecedented capability of manipulating electromagnetic waves. However, the ever-growing demand for miniaturized multifunctional optical devices requires the design and implementation of ultra-compact devices capable of integrating multiple functionalities into a single structure. Here, in this work, we proposed a single-layered all-dielectric multifunctional metadevice capable of controlling the wavefront of the incident light and exhibiting multiple optical phenomena in the ultraviolet domain. The presented meta-device exploits the spin-decoupling technique and interleaves the propagating and Pancharatnam-Barry (PB) phases to encode the multiple functionalities in it. Our meta-device consists of a super-cell having rectangular nanoantennas of silicon nitride (Si₃N₄) material arranged on a sapphire (Al₂O₃) substrate. The proposed meta-device generates three focused spots at the specified focal plane but at different positions by impinging the linearly polarized light. The presented design technique may provide an exciting roadmap toward developing and implementing multifunctional meta-devices, which will find several applications in medicine, communication, and integrated photonics.

Light-matter interaction at the micron scale enables unprecedented control over different intrinsic properties of electromagnetic waves. Recently emerged ultrathin metamaterials (metasurfaces) featuring periodic nanoantennas are capable of controlling the amplitude, phase, and polarization states of the incident light and open up new avenues for a variety of exotic nanophotonic applications. Integrating multiple optical phenomena into a single nano-optical device has become a hotspot to increase the multi-functionality of the metasurfaces for functional multiplexing, notably reducing the intricacy of the existing optical setups. Herein, a multifunctional metalens operating at ultraviolet regime 𝜆_𝑑 = 300 nm is reported, exploiting the approach of merging the Pancharatnam–Berry (PB) and propagation phases into a single metadevice. Through interleaving the different subwavelength rectangular and cylindrical shaped nanoantennas of silicon nitride (Si₃N₄) patterned on sapphire (Al₂O₃) substrate, the proposed meta-device results in a multifunctional metalens capable of focusing the incident light at three different focal spots on the same focal plane. The geometric parameters of both the nanoantennas (rectangular bar and cylindrical pillar) are optimized in such a way to achieve the maximum possible transmission intensity and complete phase coverage requirements for higher resolution focusing on making nanoscale features distinguishable. This attractive design topology of merging the multiple phases into a single device to realize a multifunctional meta-device can envision its promising application in imaging and optical communication.

Due to the recent advancement in metamaterials for bio-sensing applications, metasurfaces are designed to enhance the chirality of the incident CP light by creating chiral hotspots formed by the interaction of electric and magnetic fields. Most of the reported works focus on induced chirality in plasmonic structures operated by shifting the molecules' circular dichroism (CD) signal to plasmonic resonance frequencies, which results in a decrease in efficiency. Moreover, chiral structures like gammadions were also reported, which can enhance the chirality. Still, the inherent chirality of the structure is much larger than the chirality of the molecules and thus overshadows it. Therefore, highly efficient planar nanomaterials with broadband uniform chirality are needed to sort and detect natural and artificially-made chiral molecules. This work presents an aluminum-based dimer structure that confines the central gap's chiral field, leading to highly uniform volumetric chirality enhancement. The proposed achiral dimer structure enhances the chirality of the incident circularly polarized light without interfering with the circular dichroism (CD) of the molecules. As a result, we report high volumetric chirality and dissymmetry factor compared to the state-of-the-art, which is the figures of merit for CD spectroscopy and separation of enantiomers, respectively. This work can be applied to distinguish molecules with CD bands in the ultraviolet and visible wavelengths.

Most real-life practical applications continuously use color filters, such as holography, sensing, multicolor displays, imaging, and information encoding, etc. Conventional dye-based transparent color filters face performance degradation due to environmental threats and ultraviolet radiation. The fabrication of nanostructures, meta-devices, and absorbers is getting fast due to well-established and enhanced nanotechnology fabrication techniques. This technological advancement leads toward metamaterial-based polarization-insensitive and sensitive light filtration, which has gained incredible popularity due to its increasing color filtering applications. Here we proposed a chromium (Cr) nano-cylinders-based metabsorber for color filtering in the visible spectrum. The proposed metabsorber comprises nine cylindrical bars with a transparent silicon wafer as a substrate and 50 nm thick chromium metal as a ground plane. The total size of the metabsorber is 200 × 200 nm², whereas each cylindrical bar is 40 nm and 60 nm in diameter and height, respectively. Under simulation analysis, the proposed metabsorber depicts almost unity absorption in the visible spectrum for incident electromagnetic waves. In addition, metabsorber have passive-tunability features; specifically, it's absorption varies as the thickness of the substrate changes. Moreover, the metabsorber maintained its high absorption characteristics under large oblique incident angles (≤ 60^o). Hence, relaxed angle tolerance, polarization-insensitivity, and passive-tunability features make the proposed metabsorber an excellent candidate for color filtering in miniaturized imaging/display devices.

The ultraviolet (UV) and visible regions of the electromagnetic spectrum incorporate many exciting applications, including high-resolution imaging, optical communication, lithography, sensing, and many more. The classic ways of manipulating electromagnetic waves through bulky, large, and expensive components stand between the new technologies like on-chip systems. The advancement of nanofabrication technologies enables the advent of optical metasurfaces that can manipulate approximately the whole electromagnetic spectrum. However, the availability of a suitable and lossless material for the UV and Visible region hinders the creation of metasurfaces and their integration for practical applications. Herein, we exploit the bandgap-engineered silicon nitride (Si₃N₄) material, which is transparent in most parts of the UV spectrum and can perform efficiently in both regimes. For proof of the concept, we design and numerically simulate different metasurfaces to generate the perfect vortex beam with different topological charges and a numerical aperture of 0.6. Each metasurface is functional for both UV and visible regions and efficiently manipulates the incident light. The independence of phase profile from topological charge helps perfect the vortex beam, to control the shortcomings of the optical vortex beam. The cross-polarization efficiency of the metasurface is also up to the mark. This work may find potential applications in different fields like on-chip communication, lithography, quantum processing, and optical communication.

Metasurfaces have been playing their vital role in many fields related to light because they are capable of manipulating its characteristics. Most of the metasurfaces are based on conventional materials so they are unifunctional in the range of interest of electromagnetic spectrum. With the passage of time, the phase change materials (PCMs) have been explored which have a peculiar tendency to make multifunctional metasurface designs by tuning process. The tuning opens avenues for the drastic engineering of the optical parameters of PCMs to realize controllable devices. The stimuli for such materials are optical, electrical, thermal or mechanical activations. These PCMs based metasurfaces find numerous applications in rewritable optical volatile and nonvolatile data storage, sensors, active color displays and tunable optical switches. These materials possess high endurance and scalability, high switching speed, data retentivity, low power consumption, and reversible phase-transition in bi-stable states i.e. amorphous and crystalline forms. The Germanium antimony-tellurium ((GeTe)_m(Sb₂Te₃)_n) in its various combinations, Vanadium dioxide (VO₂), Gallium-telluride (GeTe), Indium antimonide (InSb) are PCMs to name a few. In this work, we have outlined the recent studies on different PCMs in order to explore their associated benefits for a particular application in reconfigurable, integrable, active nano-photonic metadevices. The PCMs-based structures are ideal candidates for development of next-generation, light-weight and fabrication friendly optoelectronics components to meet real-time applications based on solid-state devices. In this study, the challenges and limitations are also being highlighted related to the designs based on PCMs.

A gold nanoparticle enhanced microwave modulation with 1.55 μm light in graphene-based antenna has been studied in this paper. The modulation of antenna radiation is achieved by the conductivity tunable characteristic of graphene, and the conductivity of graphene is controlled by light. With the introduction of the gold nanoparticles for exciting optical wave localized enhancement, the interaction between the graphene and the light is enhanced. And then the Fermi level is enlarged, leading to the enhancement of the conductivity turning rage of graphene. At last, the modulation of microwave radiation is enhanced. In the simulation, as the Fermi level of graphene increases from 0.1 eV to 0.4 eV, the S11 coefficient of resonant point of antenna changes by 8 dB. In the experiment, the 0-29.4 mw 1550 nm light is used, the S11 coefficient of graphene antenna with gold nanoparticles changes by 1 dB, which is 2 times higher than that of graphene antenna without gold nanoparticles. The result demonstrates that the microwave modulation by light in graphene-based antenna could be enhanced by gold nanostructures with the localized surface plasmons.

Dielectric mesoscale spheres have aroused strong interest because of their potential to localize light at deep subwavelength volume and to yield extremal internal magnetic and/or electric field enhancements. Recently, it was showed that such particle could support high-order Mie resonance modes with giant field localization and enhancement. Optimizing the internal fields appears as a key challenge for enhancing wave matter interactions in dielectric mesoscale particles. However, a dielectric particle is always located in some medium, and not in a vacuum. Moreover, the question is how much the environment medium affects the internal field intensities enhancement in the super-resonance effect. Based on Mie theory we show for the first time that the presence of the environment leads to a significant decrease in the intensity of the field in the particle. Thus, the study of the effect of super-resonance becomes meaningless without taking into account the environment. However, a greater enhancement of the internal field is found for the blue-shifted Mie size parameter of the sphere when the particle, for example, is in air rather than in vacuum.

Optical nanoantennas, made of metallic or dielectric materials, have seen a rapid development for their remarkable optical properties facilitating the coupling of electromagnetic waves with subwavelength entities. However, highthroughput and cost-effective fabrication of these nanoantennas is still a daunting challenge. Here we provide a versatile nanofabrication method capable of producing large scale disk-shaped optical nanoantennas. It is developed from colloidal lithography with no dry etching required. Furthermore, both metallic and all-dielectric nanodisks can be readily fabrication in a high-throughput fashion. We believe that this nanofabrication method could find a wide range of applications with the diverse optical nanoantennas it can engineer.

Thrombus formation issues play an important role in the occurrence, diagnosis and treatment of cardiovascular diseases. The inhibition of platelet aggregation is currently the main therapeutic approach in treatment and prevention of cardiovascular diseases. Understanding the platelet structure and its spectral response to the antiplatelet therapy is the key to personalized medicine today. According to the World Health Organization (WHO) reports, cardiovascular deceases have been remaining the leading cause of death at the global level for the last two decades. The number of deaths has been increased up to nearly 9 million in 2019 [1]. The COVID-19 pandemic has resulted in cardiovascular decease (CVD) increase, which caused deaths in many countries [2-3]. The paper presents studies of the fluorescence intensity of aromatic amino acids namely tyrosine (Tyr) and tryptophan (Trp) in the presence of spherical rhodium and platinum nanoparticles (Rh and Pt NPs).

An influence of the periodic modulation of the magnetization on the magneto-optical effects in the nanostructures was studied. It was revealed that the periodic spatial distribution of the magnetic response in the ferromagnetic part of the nanostructure leads to the appearance of the periodic modulation of both transverse magneto-optical Kerr effect as well as the Faraday effect. In case of a coincidence of magnetization modulation period and spatial length of the excited optical mode in the nanostructure the magneto-optical effects become resonantly enhanced. There are addressed plasmonic metal/dielectric nanostructures as well as the silicon/ferromagnetic dielectric structures.

The detection of glucose level in human body is very necessary for motoring physical condition. In our work, a triple tapered sensor probe based localized surface plasmon resonance (LSPR) is developed to detect various glucose concentration solution. The single-mode fiber (SMF) is utilized to prepare the proposed triple tapered structure. The serial taper structure in the sensing area insure more evanescent wave (EW) leak out. Gold nanoparticles (AuNPs) are modified on the serial triple tapered fiber (STTF) structure to stimulate the LSPR phenomenon. The limit of detection (LOD) and sensitivity of sensor are 3.8 mM and 0.59 nm/mM, respectively. Moreover, the reproducibility, selectivity, pH test, and reusability of STTF probe are evaluated to validate the ability in practice.

Fiber-tip lens not only makes the optical system more flexible and compact, but also eliminates complex alignment process, which makes it widely used in the fields of spatial light-fiber coupling, laser direct writing and fiber optic imaging. Compared to traditional glass lens, metalens is easier to be processed and integrated on fiber tip because of its special planar structure and small footprint. Fiber-tip metalens with high efficiency achromatic focusing ability has great application potential in multimode endoscope and other optical fiber imaging systems, so we designed a metalens with Si nanopost array that can achieve broadband focusing in the wavelength range of 1.2μm - 1.6μm. For realizing broadband achromatic focusing, it is the crucial to meet the focusing phase and phase dispersion requirements simultaneously. Then we built a library of unit pillars with three kinds of cross-sectional geometries to provide diverse focusing phase (φ) and phase dispersion (δφ) combinations and defined a phase-dispersion space composed of parameters. In order to find the optimal unit pillar at each cell, we regarded the minimum Euclid distance between the points from the library and the target point in the phase-dispersion space as the criterion. Photonic crystal fiber (PCF) is a suitable integration platform for metalens because of the large core diameter and good dispersion property, so the PCF guided mode and plane wave are selected to lunch into the metalens for comparison and verification in the present work. The simulation results demonstrated that the metalens had a good achromatic focusing performance in the target wavelength band and changed little at different polarization of the source, which showed a good polarization-insensitive property.

Optical phased array has the advantages of low cost, small size, and high stability. It has broad application prospects in Lidar, free space optical communication, and so on. Among all of them, SiN photonic integrated circuit platforms have received much research. Compared to Si, SiN has smaller optical nonlinear effects and waveguide losses, allowing higher optical power to be emitted. However, the refractive index of SiN is smaller than Si. The pitch of SiN-based waveguides and waveguide grating antennas is larger to reduce crosstalk. This results in a smaller field of view for SiN optical phased arrays and reduces the power ratio of the main lobe to the total emission. In this work, we spaced two SiN waveguides with different propagation constants to reduce the coupling strength between adjacent waveguides. In the range of 1500 nm to 1600 nm, the crosstalk is smaller than -29 dB at the waveguide pitch of 2 μm. In this case, the field of view of the optical phased array reaches 43.89° × 8.47° (ψ × θ). For the optical phased array with 512 channels and a 1 mm long antenna, the divergence angle is 0.078° × 0.086° (Δψ × Δθ). The small spot achieves higher resolution and high point cloud density.

In this paper, in view of mode field matching problem between the anti-resonant hollow-core optical fiber and the conventional optical fibers. We introduce an intermediate SMF fiber with thermal expanded core (TEC) at one end as a transition fiber; at the same time, when we fusion splicing, we use multiple heating methods to avoid the transitional collapse of optical fibers. The optical fiber rotation method is used to monitor the change of optical power and achieve high matching to the shaft to obtain a higher extinction ratio.

We proposed a multilayer infrared metamaterial absorber with metal-insulator-metal (MIM) stacks and patterned nanostructured surfaces for ultra-broadband infrared applications. Chromium (Cr) and silicon dioxide (SiO2) were designated as the main materials of the absorber considering assessing the real functionalities of several metals and insulator materials in the structure. Furthermore, the electromagnetic field distribution shows that the stacks of different MIMs above the structure excite absorption peaks in distinct wavelength ranges, and the absorption range can be enlarged by manipulating structural parameters. The average absorptivity is higher than 80% throughout a wide wavelength range of 780 nm to 5500 nm, according to results of numerical simulation. The absorption spectrum encompasses the entire near-infrared and mid-infrared range, and it has promising applications in spectral sensing, infrared light sources, and detectors.

Optical phased array has great potential in the fields of light detection and ranging, free-space optical communication, laser imaging and biosensors due to their excellent characteristics such as all-solid-state structure, fast scanning speed, good stability, high resolution and low cost. According to the radar equation, the transmit power will directly determine the maximum ranging distance of optical phased arrays. Limited by nonlinear effects and damage threshold, it is difficult to further increase the input optical power of Si-based OPA above 30 dB. Therefore, fully utilizing the input optical power of OPA is an important issue in the research. In this paper, we demonstrate a novel three-layer silicon antenna for OPA, which consists of a upside grating layer, a waveguide layer and a downside grating layer from top to bottom. In the simulation, we found that the upward directivity of the antenna is greater than 60% in a large wavelength range of 1413 nm to 1875 nm. In addition, the maximum upward directivity of the antenna is 94.68% at 1599nm. The above result is beneficial to increase the output power of the phased array and eliminate the blind area in the field of view when the beam is scanned to the point of destructive interference. Overall, the above results show that the design proposed in this paper has great potential for application.

We presented an all-dielectric metasurface optical refractive index sensor based on four fan-shaped holes that produces two Fano resonances in magnetic dipole (MD) modes, with maximum sensitivity (S) and figure of merit (FOM) of 225 nm/RIU and 750, respectively.

The surface modification strategy is widely used to solve the problems of low stability, agglomeration, surface oxidation and photoluminescence quenching of quantum dots (QDs) in practical applications. However this method can easily destroys the surface ligands of QDs, increases defects even leads to a huge loss of fluorescence. In order to improve the stability of QDs, a new synthesis method of QD-silica hybrid nanospheres was proposed in this study. These QD-silica hybrid nanospheres are characterized by using mesoporous silica spheres (MSSs) as template, adsorbing QDs as one shell, and then coating a silica layer as another shell (named SQS). The template MSSs were functionalized by (3-mercaptopropyl) trimethoxysilane (MPTMS) in order to connect MSSs and QDs. After that, the QD-adsorbed silica spheres were coated with silica as the encapsulation layer by Stober method. The structure and morphology of SQS were analyzed by TEM. The effects of different contents of MPTMS and tetraethoxysilane(TEOS) were experimentally compared. Finally, it was found that the optimal contents of MPTMS and TEOS was 250μL and 1.5mL, respectively. The luminescence intensity of SQS samples could reach 2 times higher than that of pure QD solution. Meanwhile, SQS hybrid nanospheres could avoid the tiny spots inside the microstructure caused by QD aggregation and play a better role in dispersion.

The key to developing a new type of liquid crystal display (LCD) lighting is to balance light quality with high light efficiency, and the light diffusion plate is an indispensable part of LCD to achieve different light extraction efficiency and light uniformity. In addition, the addition of quantum-dots (QDs) further improves the light transmittance and optical conversion efficiency of the light diffusion plate. In this paper, the surface engineering method was used to prepare QDs composites to improve the stability of QDs diffusion plate under high temperature and humidity. This paper briefly introduced the light diffusion plate, and then discusses the preparation of the QDs composites and the injection molding process of the QDs diffusion plate. Finally, the QDs diffusion plate was assembled into a backlight module, and its stability was tested at 60℃ and 85% relative humidity (RH). The experimental results show that the spectra and external quantum efficiency (EQE) of the QDs diffusion plate do not change significantly after long time storage at high temperature and humidity. This experiment improved the stability of QDs diffusion plate and lays a foundation for the subsequent large-scale production.

Multiple Fano resonances have become an effective means to design optical devices in all-dielectric metasurface. A silicon array-based metasurface structure is proposed in this paper, in which a silicon layer is placed on a silica substrate. Each unit structure is a cube with a square cross section and two half-cylinder etched holes with a cuboid etched hole in the middle. Asymmetry was created by changing the radius of one of the two half-cylinders, resulting in a tunable quasi- BIC mode. As a result, two new Fano peaks with Q values more than 10000 have been discovered, reaching 1.3×10⁴ and 1.5×10⁴ respectively. The highest sensitivity is calculated to be 277.5nm/RIU, while the maximum FOM value is 1387.5, indicating good sensing performance. It is believed that the proposed structure can provide inspiration for the applications of nonlinear optics, optical switches and biochemical sensors.

Atmospheric suspended particles are an important component of atmospheric pollutants and pose a great threat to human health and the ecological environment. Suspended particles have various properties such as wide size distribution, complex composition and morphology (including porous structure). Particles with porous structure usually have a larger internal surface area and will adsorb more toxic substances. In the present work, we developed an algorithm to generate particles with porous structure and adjustable pore size. Then we used Discrete Dipole Approximation (DDA) method to calculate the light scattering matrix of particles with different pore sizes and study the effect of pore size on their light scattering properties. In order to obtain polarization indicators to characterize pore size, measured the polarization scattering signals of porous particles at four different angles, namely 30°, 60°, 85° and 115°. The combination of simulation and experimentation provides the basis for future identification of porous particles and differentiation of particles with different pore sizes. This work will facilitate real-time monitoring of porous particles with high adsorption capacity of toxic and hazardous substances in the field of environmental protection.

Arbitrarily control of electromagnetic field in femto-nano spatiotemporal scale can be realized by illuminating metallic nanoparticle with well-defined femtosecond laser pulse, which is at heart of current ambitious research endeavors in nanophotonics. However, the quantitative relation of the behavior of localized field with the incident laser pulse hasn’t yet been revealed. Here, active switching of localized near field is achieved by single chirped laser pulse in asymmetric Au nanocross system within the pulse duration using Finite Differential Time Domain algorithm. Temporal interval of energy switching between the two poles of nanocross is determined by the chirp of the laser pulse According to the temporal evolution, we found that field enhancement is asymmetric for positively and negatively chirped pulses as the consequence of the imbalance response of the plasmonic field around resonant frequency. It is demonstrated that under the excitation pulse of specific spectrum, field enhancement can also be effectively modulated by chirped laser pulse, providing a new degree of freedom for manipulating the dynamics of localized surface plasmons in nanoparticle.

In recent years, with the research of metamaterial structure absorbers and the concept of plasma perfect absorber, the perfect absorbers have developed from single-band absorption to multi-band absorption, broadband absorption, and narrow-band absorption. At present, in order to achieve a wider band, great efforts have been made to develop absorbers using multi-layer structures and nanostructured designs. However, the preparation and processing process such as Electron Beam lithography, Interference Lithography, Nanoimprint Lithography, etc., are too complicated and manufacturing costs are high, resulting in the difficulty of large-area preparation. It will seriously limit the practical application of broadband perfect absorber. In addition, multi-band perfect absorbers in the ultraviolet, visible and near-infrared regions are rare and suffer from a lack of bandwidth, while the application of broadband perfect absorbers in solar cells, cloaking technology, detection and sensing has become an urgent problem. Therefore, the design and implementation of broadband perfect absorbers that can be manufactured in a simple way for mass production has become a hot topic of research. Based on the advanced theory of artificial metamaterials and the principle of impedance matching, a MIM structured broadband perfect absorber based on an array of nanospheres has been designed. The absorber consists of an array of nanospheres with a metal-medium-metal structure, which enables ultra-broadband perfect absorption. The metal materials of the absorber are platinum (Pt) and gold (Au), the media material is aluminum oxide (Al₂O₃). The absorption spectrum and electromagnetic field energy distribution of the absorber, as well as the influence of the incidence angle and cell structure size on the absorption performance, were studied and analyzed by COMSOL Multiphysics. Numerical calculations show that the absorber has an average absorption of more than 95% in the visible-near infrared range (400-1400nm). The broadband absorption is achieved by a combination of modes, mainly surface plasmon and Fabry-Perot resonance. This absorber can replace the micro and nano processing process with self-assembly technology, which can achieve low cost, high efficiency, broad bandwidth and large area fabrication.

The calculation of thermal shifts caused by the absorption of laser radiation power is extremely important for describing nonlinear processes in microresonators. One way to calculate thermal frequency shifts is to use equations with effective parameters. In our work we calculated the effective parameters by approximating the numerical solution of 3D heat equation in Si₃N₄ integrated microresonator pumped by a ”step-like” heating power with the empirical exponent and found that the quality of the approximation depends on the geometric and material parameters of the microresonator. As result we obtained the map of parameters where the commonly used equation describes the direct numerical simulation well and the range of parameters where the applicability of this theory becomes inaccurate. To verify the correctness of our calculations, we compared the frequency shifts calculated using effective parameters with frequency shifts obtained with numerical simulation of eigenfrequencies and eigenmodes problem in a ”hot” deformed microresonator.

We upgraded the original fabrication method based on melting commercially available ZBLAN (heavy metal fluoride glass) optical fiber to obtain high-quality-factor ZBLAN microspheres with a diameter of 250 to 400 μm. The whispering gallery modes were excited in fabricated microresonators by different coupling elements and the high Q-factors at both 1.55 μm and 2.64 μm were demonstrated. At 1.5 μm the intrinsic Q-factor of (5.4 ± 0.4) · 10⁸ determined by material losses was obtained. For 2.64 μm the quality factor was measured as (1.13 ± 0.22) · 10⁸.

Electro-refractive optical modulator is an optical device using the refraction principle of the light, which is related directly to the refractive index of a material, to modulate an optical signal via an applied external electric field. For multiple quantum well (MQW) materials, taking the advantage of the quantum-confined Stark effect (QSQE) to investigate the change in the absorption coefficients and refractive index, we calculated the refractive index for Ge/SiGe MQW and investigated optical characteristics of the electro-refractive modulation using Ge/SiGe MQW by FDTD and MODE Ansys lumerical simulation. We have found that the use of MQW materials might potentially contribute to an efficient electro-refractive modulation.

In this paper, numerical experiments are conducted to explore quantum scattering, resonant tunneling, and decay probability along with transmission and reflection coefficients. Finite element method is used with Ben Daniel-Duke boundary conditions which are applied on the interfaces and Dirichlet and Neumann boundary conditions on outer boundaries. We have accomplished a study in which barrier width is changed from 1nm to 6 nm by keeping dot width constant 10nm. Al_xGa1-_xAs with concentration of 0.32 and bandgap (E_g (Γ)) of 1.84 eV is used. GaAs with bandgap (E_g (Γ)) of 1.42 is used as barrier material. The total width is 40 nm. The wave functions of the electrons penetrate through the quantum wells using time-independent Schrödinger equation are calculated and applied on the GaAs/Al_xGa_1-xAs quantum well to see the behaviors of wave functions in resonant tunneling, scattering and their total decay probabilities by changing width of barrier. The Hamiltonian is calculated by effective mass approximation and finite element method is used to find the energies and potential well. Four studies are set up to discuss different aspects related to the proposed structure. First, the eigen energies are solved for the quasi-bound states using an eigenvalue study, with open boundary conditions for outgoing waves at both ends of the modeling domain. Then, the time evolution of one of the quasi-bound states is solved in a time-dependent study. Next, the resonant tunneling condition is solved in an eigenvalue study, with a special type of open boundary condition for incoming waves on one end of the modeling domain. Finally, the transmission and reflection coefficients are computed using a stationary study, with regular open boundary conditions and a prescribed incoming wave from one end of the modeling domain. The eigen energies can be computed analytically using the transfer matrix method. The time evolution of the quasi-bound states wave functions as the initial condition.

The paper describes the results of finite-difference time-domain (FDTD) mathematical modeling of electromagnetic fields distortion near the planar SIO₂ surfaces modified with gold nanostars. The calculated field values were converted into the electromagnetic field enhancement coefficient and the surface-enhanced Raman scattering (SERS) intensity. Prospects of the theoretical approach for planar SIO₂ surfaces modified with gold nanostars modeling to evaluate optimal field amplification and light-scattering parameters have been shown. The presented approach could be applied as a basis for performing methods of controlled synthesis of effective SERS-based biocompatible sensors.

The effect of the thickness of the polyvinyl alcohol film on the position of the plasmon maximum at the modified titanium-dielectric interface was investigated. The integration of bismuth oxide, thulium oxide, as well as their mixtures into thin polymer films (thickness of up to 1.3 μm) was carried out. It was established that the spectral shift of the plasmon maximum into the red region of the spectrum is due to the roughness features of the titanium surface as a result of anodizing and due to the thickness of the PVA film. The presence of the overlap in the reflection spectra of thulium oxide and bismuth oxide has been established, which leads to a complete leveling of the spectral band of thulium oxide in the region of 350 nm.

2D problem of the diffraction of the TM cylindrical electromagnetic wave by cluster considering of two silicon carbide SiC (6H-SiC modification) cylinders is considered. Rigorous numerical procedures are used to study Plasmon resonances in such clusters. Frequency characteristics for the scattering cross section, the field distribution on the cylinder’s surface and spatial structure of the field in the vicinity of the clusters was calculated for symmetrical and nonsymmetrical excitation by the cylindrical wave, different diameters of the cylinders, distances between cylinders and loss of 6H-SiC medium. It was found two different types of Plasmon resonances are taking place in terahertz wavelength range 10.3 μm – 11.0 μm.

The metal nanoparticle (MNP) can lead to significant reshaping of spectral features in the three level Λ system. For this a master equation is derived with the Born-Markov approximation, but in place of bare states, it’s the dressed states transitions which are coupled to reservoir. This master equation gives many new interesting terms which are not present in traditionally derived master equations. The dressed state-reservoir coupling results in sampling of Local density of states (LDOS) by the dressed state transitions causing asymmetricity in the spectrum.