A high-power monolithic continuous-wave fiber amplifier at 1064 nm has been demonstrated based on a piece of confined ytterbium-doped fiber, which generated 3.5 kW narrow-linewidth laser with near-diffraction-limited beam quality. By tailoring the diameter of gain dopant across the fiber core, and optimizing the profile of refractive index and doping concentration, the confined doping fiber works making

We present a rigorous design of few-mode erbium doping fiber (FM-EDF) with an oversized two-layer erbium ion distribution at the central region with effective differential modal gain (DMG) mitigation over the C-band. The proposed erbium doping distribution allows for a similar overlapping integral value among the guided modes, leading to a signal gain equalization over the C-band. When the length of

Using few-mode fiber to receive spatial light is an important method to obtain high coupling efficiency in long-distance free space optical communication systems. Here, we deal with the influence of random angular jitter on few-mode fiber coupling. First, the expression of mean-coupling efficiency from a spatial plane wave to few-mode fiber in the presence of random angular jitter is given. We find

In this paper, a novel, to the best of our knowledge, surface plasmon resonance (SPR) fiber biosensor is theoretically proposed to detect the surrounding refractive index based on a Stampfli-type photonic quasi-crystal fiber with one air hole coated gold thin film. Surface plasmon polaritons (SPPs) at the metal/dielectric interface are excited by the orbital angular momentum (OAM) mode (other than

A new, to the best of our knowledge, hollow-core optical fiber based on a tube lattice geometry is proposed. The fiber cross section is formed by eight tubes with five different thicknesses, and the guidance mechanism is based on the inhibited coupling phenomenon. As such, its transmittance spectrum displays low-loss windows intercalated with high-loss regions, each of the latter related to specific

Self-action of an initially elliptically polarized Gaussian beam in the isotropic phase of a cholesteric liquid crystal near the temperature of phase transition is studied. It is shown that nonlocality of the optical properties of the crystal leads to significantly different self-action behavior of light beams with right-hand and left-hand elliptical polarization. Numerous lines of circular polarization

Whispering gallery (WG) microcavities have been applied for a variety of optoelectronic devices due to their extraordinary characteristics of high quality factor ($Q$) and small mode volume, crucial to accurately tune the quality factor for realizing the high-speed optical modulation and short pulse laser. In this paper, we propose and theoretically analyze a hybrid, graphene-coupled silica microtoroid

A photonic hook (PH) is a high-intensity, curved focusing beam with a subwavelength waist based on the photonic nanojet effect. It is generally created by illuminating mesoscale transparent particles using optical plane waves. In this work, we numerically explore the generation of the PH supported by the Janus microcylinder under point-source illumination. To simulate the photonic intensity distributions

A magnetic field vector sensor based on a cascaded structure composed of a core-offset Fabry–Perot interferometer (FPI) and a magnetic fluid (MF) infiltrated glass capillary (GC) is proposed and demonstrated. An air-gap FPI with a cavity length of 85 µm is formed by core-offset fusing two single-mode fibers separated by a short hollow-core fiber (HCF). The FPI is cascaded with an MF-infiltrated GC

In this work, we present a fiber-based setup for femtosecond pulse generation at $\sim910 - 940\;{\rm nm}$ wavelength. Pump pulses from a Mamyshev oscillator with center wavelength at 1036 nm 1 ps duration are amplified and coupled into a photonic crystal fiber forming a soliton at 1051 nm. Due to the nonlinear four-wave mixing process, soliton pulses are converted to 910–940 nm with a few hundred

The polarization state in a double-corner-cube-retroreflector (DCCR) ring cavity is analyzed using Jones matrix. Based on the analysis results, an output coupling ratio tunable DCCR ring cavity created by employing a polarization beam splitter, and wave plates (including $\lambda /{2}$ plate and $\lambda /{4}$ plate) is studied theoretically and experimentally. The theoretical output coupling ratio

As a plasmonic absorber for short-wavelength infrared hyperspectral imaging, a silicon-coated gold nanodiffraction grating structure is proposed. This plasmonic absorber leads to absorption peaks in short-wavelength infrared region by the high refractive index of silicon coating on gold grating. It is relatively easy to fabricate with smaller size than those of already known absorbers. By performing

An analytical model for a square split ring resonator (S-SRR) having a single split-gap is considered here to reliably estimate the fundamental resonance frequency of the ring. An S-SRR is assumed to be equivalent to a series-resonant LC loop. The approximate formulas for equivalent self-inductance and total capacitance of the ring are derived separately. The total capacitance of the ring is expressed

We present a rigorous theoretical framework for designing full-space spatial power dividers using metagratings. In our study, the current restrictions of spatial power dividing platforms such as reflection-only performance, operating at normal incidence, and small reflection/refraction angles have been totally relaxed. A modal expansion analysis based on the Floquet–Bloch theorem is established so

Slotted photonic crystal (SPC) cavities provide strong evanescent fields, high quality factors, and small mode volumes. Hence, SPC cavities have been identified as promising candidates for the implementation of high-performance sensors and the development of hybrid devices combining silicon with other active materials. Nevertheless, most state-of-the-art demonstrations rely on electron beam lithography

A non-stationary one-dimensional cavity can be described by the time-dependent and multi-mode effective Hamiltonian of the so-called dynamical Casimir effect. Due to the non-adiabatic boundary conditions imposed in one of the cavity mirrors, this effect predicts the generation of real photons out of vacuum fluctuations of the electromagnetic field. Such photon generation strongly depends on the number

Surface plasmonic resonance (SPR) is integrated into a whispering-gallery mode (WGM) optical microsensor to augment sensitivity in this study. The performance of such WGM silica ring sensors of 20 µm in size with an Ag or Au metal core was evaluated for detection of small respiratory viruses such as COVID-19 via the finite-element modeling. Compared with pure WGM sensors, the integration with SPR enhances

The pendular spectra of linear ${({\rm HCCCN})_n}\;({\rm n} = {1 {-} 3})$ molecules at several rotational temperatures under a certain range of electric field strength $E$ are calculated using the finite element matrix diagonalization method. In addition, the normalized “$Q$-branch” intensity $({I_Q})$ and the gradient $({K_E})$ of ${I_Q}$ under corresponding conditions are investigated. Based on the

Higher-order mode conversion plays a vital role in on-chip multimode applications. Here, we propose an efficient silicon-based higher-order mode conversion scheme that can achieve the mode-order conversion from ${{\rm{TE}}_0}$ to ${{\rm{TE}}_1}$ (${{\rm{TE}}_0} {-} {{\rm{TE}}_1}$) mode and from ${{\rm{TE}}_0}$ to ${{\rm{TE}}_2}$ (${{\rm{TE}}_0} {-} {{\rm{TE}}_2}$) mode, respectively. These mode conversion

Fano resonance is based on a plasmonic metasurface and has many applications in various fields. In this paper, we propose an independently adjustable graphene-based double-layer grating structure. We control multiple Fano resonances at different wavelengths and bandwidths by regulating the Fermi level thanks to the preeminent characteristic of graphene. Here, the equivalent resonator coupled-mode method

We propose a digital filter design method for high-order series-coupled microring resonator (MRR) filters considering coupling loss in coupling areas. This method makes it possible to design high-order MRR filters with desired parameters such as a 3 dB wavelength bandwidth, free spectral range (FSR), and center wavelength, which have been difficult to design so far. It is possible to apply the proposed

A compact and broadband mode demultiplexer (DEMUX) using a subwavelength grating (SWG) engineered multimode interference (MMI) coupler is proposed and analyzed in detail. To effectively separate the input ${{\rm TE}_0}$ and ${{\rm TE}_1}$ modes, the input port is formed by cascading two tapers, connected by a silicon wire, in a single SWG MMI coupler. Moreover, by partially tailoring the grating duty

The closed aperture continuous wave Z-scan of L-tryptophan at 661 nm was performed to investigate the variation of on-axis nonlinear phase shift $({\Delta {\Phi _0}})$ with the change of optical field strength. $\Delta {\Phi _0}$ was found to vary nonlinearly with irradiance (${I_0})$ in the range from 150 to ${{290}}\;{\rm{\;{\rm MW}/}}{{\rm{m}}^2}$. This nonlinear variation is explained by considering

Optoelectronic oscillators (OEOs) have attracted much attention for producing ultra-low phase-noise microwave/millimeter-wave oscillations. Traditional delay-based OEOs usually suffer from strong spurious peaks in their phase noise power spectral densities and possible mode-hopping phenomena. Some methods have been proposed in the literature such as using multi-loop architectures or injection locking

In this paper, a periodic superconducting structure (PSS) with a multiwindow spin Hall effect (SHE) is proposed. Through using the multipeak and angle-sensitive characteristics of the evanescent wave, transmission defects at different angles are achieved for $p$ waves and $s$ waves. Based on this, the multiwindow SHE can be obtained by controlling the number of transmission peaks. Both the horizontal

Multifocal microscopy affords fast acquisition of microscopic 3D images. This is made possible using a multifocal grating optic; however, this induces chromatic dispersion effects in the point spread function, impacting image quality and single-molecule localization precision. To minimize this effect, researchers use narrow-band emission filters. However, the choice of optimal emission filter bandwidth

The principal limitation in many areas of astronomy, especially for directly imaging exoplanets, arises from instability in the point spread function (PSF) delivered by the telescope and instrument. To understand the transfer function, it is often necessary to infer a set of optical aberrations given only the intensity distribution on the sensor—the problem of phase retrieval. This can be important

This feature issue presents original work on light-matter interaction in complex photonics systems, which has been a continuously growing area of optics and photonics, in terms of both importance and breadth. From disordered systems to highly controlled micro- and nanostructures, recent decades have witnessed the onset of random media, photonic crystals, metamaterials, plasmonics, and, more recently

Vertically aligned Al-doped ZnO nanorods (AZO-NRs) were grown on glass substrate using a chemical bath deposition (CBD) method at various temperatures between 80°C and 130°C. The results showed the Al content in the AZO-NRs strongly depends on the growth temperature. The optimum doping level was attained at 110°C. The morphology was maintained in each sample, and the lasing properties were investigated

We build on former results from our work on parity-time symmetric gratings implemented in 1550 nm distributed-feedback laser diodes to address the design issues raised by the first trends we observed. These laser diodes are of a complex-coupled nature, with modulations of both real and imaginary parts of the effective index, with a relative phase related to the parity-time symmetry. The unidirectionality

Dielectric metasurfaces control optical wavefronts via nanoscale resonators laid out across a surface. However, most metasurfaces are, by design, planar. In this work, we demonstrate the ability to fabricate dielectric metasurfaces with vertically oriented dielectric resonators using membrane projection lithography. We first numerically characterize the resonant modes of an array of vertically oriented

By using tailored disorder in the regime of diffusive light propagation, core-shell cloaking structures have previously been presented. These structures make the cloak and an arbitrary interior nearly indistinguishable from the diffusive surrounding. This statement holds true for all incident polarizations of light, a broad range of incident directions of light in three dimensions, and a broad range

We report the experimental realization of a multifunctional microscale plasmonic metasurface capable of sampling a light beam and performing five functionalities, while allowing high direct transmission and maintenance of the properties of the input light beam. The plasmonic metasurface integrates light-to-surface-plasmon coupling, two-channel wavelength demultiplexing with a channel spacing smaller

Surface lattice resonances (SLRs) emerging in regular arrays of plasmonic nanoparticles (NPs) are known to be exceptionally sensitive to the homogeneity of the environment. It is considered necessary to have a homogeneous environment for engineering narrowband SLRs, while in a half-space environment, SLRs rapidly vanish as the contrast between the refractive indices of the substrate and superstrate

Metasurfaces with dynamic optical performance have the potential to enable a broad range of applications. We computationally investigate the potential of dielectric Huygens metasurfaces, supporting both electric and magnetic dipole resonances, as a candidate platform for dynamic tuning. The asymmetric response of the two dipole resonances to changes in geometric and material parameters, and the potential

Due to several advantages over conventional devices for the control of electromagnetic (EM) radiation, the demand for metasurface utilization based on artificially engineered micro and nanostructures is boosted, especially in new generation devices. Among the metasurfaces family, there has been a growing interest in Huygens’ metasurfaces that are easy to fabricate due to their lower aspect ratio compared

Opening the terahertz electromagnetic band to a wealth of applications still requires the development of new devices. For example, effective means to filter, modulate, and route terahertz beams are still required for terahertz communications, spectroscopy, and sensing to achieve their promise. In particular, metasurfaces are widely discussed for future 6G wireless communications systems. These applications

Graphene-based metasurface nearly perfect absorbers (MPAs) can be used as an efficient tool for the active control and manipulation of waves in the terahertz (THz) gap. Here, we propose a novel, to the best of our knowledge, graphene-based MPA that is designed based on a simple configuration and is capable of absorbing THz radiation within a broad bandwidth of almost 3 THz with polarization-insensitive

Metasurfaces constitute an emerging technology, allowing for compact manipulation of all degrees of freedom of an incident lightwave. A key ongoing challenge in the design of these structures is how to allow for energy-efficient dynamic (active) operation, particularly for the polarization of incident light, which other standard devices typically cannot efficiently act upon. Here, we present a quasi-two-dimensional

The inherent weak nature of chiroptical signals provided by typical polarimetric measurements of natural optically active media has led to the development of different techniques to achieve enhanced chiral sensing. Intuitively, the introduction of gain could provide the desired enhancement; however, this requires gain media that can couple directly to the chiral medium. Here, it is shown that nanophotonic

An artificial magnetic response is not only intellectually intriguing but also key to multiple applications. While previously suitably structured metallic particles and high-permittivity dielectric particles have been used for this purpose, here, we highlight the possibility of exploiting lattice effects to significantly enhance an intrinsically weak magnetic dipole moment of a periodically arranged

Optical-field emission from nanostructured solids such as subwavelength nanoantennas can be leveraged to create sub-femtosecond, petahertz-scale electronics for optical-field detection. One application of particular interest is the detection of an incident optical pulse’s carrier–envelope phase (CEP). Such CEP detection requires few-cycle, broadband optical excitation where the resonant properties

We report the demonstration of an instantaneous frequency measurement system based on the four-wave mixing (FWM) effect in short dispersion engineered slow-light silicon photonic crystal waveguides for RF frequency measurement purposes within a range of 10 MHz to 80 GHz. Three nonlinear media were investigated including 3 mm ridge waveguide, 80 µm nanowire, and 80 µm photonic crystal (PhC). The system

For an ensemble of nonlinear systems that model, for instance, molecules or photonic systems, we propose a method that finds efficiently the configuration that has prescribed transfer properties. Specifically, we use physics-informed machine learning (PIML) techniques to find the parameters for the efficient transfer of an electron (or photon) to a targeted state in a nonlinear dimer. We create a machine

Nonlinear optical (NLO) properties of materials can be enhanced by assembling them as thin polymer composite films alternating with other polymers and forming dielectric mirrors, 1D photonic crystals (1DPCs), wherein the input light intensity is increased. Based on the poly(vinyl carbazole) (PVK) and poly(vinyl alcohol) (PVA) contrasting polymer pair, variants of such structures, with graphene and

The general concept of Fano resonance is considered so as to show the possibility of this resonance in space. Using a recently found solution for a Bessel wave beam impinging on a dielectric sphere, we analyze the electromagnetic fields near a microsphere with different optical sizes and permittivity values. We theoretically reveal spatial Fano resonance when a resonant mode of the sphere interferes

In this paper, we propose a novel approach to enhance the efficiency of the two-photon spontaneous emission process that is driven by the multifractal optical mode density of photonic structures based on the aperiodic distributions of Eisenstein and Gaussian primes. In particular, using the accurate Mie–Lorenz multipolar theory in combination with multifractal detrended fluctuation analysis, we compute

We have developed a rigorous scattering matrix theory of light emission from periodically structured media using a Green’s function approach. We computationally simulate the spectral power inside the structure, incorporating Purcell factor enhancements, and find internal waveguiding modes and plasmonic losses. We simulate the light-outcoupling factor ${\eta _{\text{out}}}$ and describe how corrugations

An analysis of spectral response apodization by duty cycle methods for grating-assisted optical filters is presented. The study is performed for the case of codirectional couplers, Bragg reflectors, and mirrors. The modeling results show that the supersymmetric duty cycle (SDC) modulation method, initially considered for parity–time symmetric gratings in Lupu et al. [IEEE J. Sel. Top. Quantum Electron

This work considers the near-infrared range diffraction radiation (DR) from a modulated beam of particles passing between two identical dielectric circular nanowires covered with graphene. The resistive boundary conditions are set on the zero-thickness graphene covers with the electron conductivity determined from the Kubo formalism. Assuming that the beam velocity is fixed, we use the separation of

Beyond the extensively studied microcavity polaritons, which are coupled modes of semiconductor excitons and microcavity photons, nearly 2D semiconductors placed in a suitable environment can support spatially localized exciton–polariton modes. We demonstrate theoretically that two distinct types of such modes can exist in a photonic crystal with an embedded transition metal dichalcogenide (TMD) monolayer

The polarization state of light scattered by a two-dimensional array of spherical particles is considered based on the statistical approach. The impact of filling factor, particle size, and the type of their spatial order is analyzed for arrays of silicon and silica scatterers. The conditions are formulated to suppress the $p$ and $s$ components of light specularly reflected by the array of any size

In entangled two-photon absorption (eTPA) spectroscopy, information about the energy-level structure of an arbitrary sample is retrieved by Fourier transforming sets of measured two-photon absorption probabilities of entangled photon pairs where the degree of entanglement and the delay time between the photons are varied. This works well for simple systems but quickly becomes rather difficult when

Linear optical quantum gates have been proposed as a possible implementation for quantum computers. Most experimental linear optical quantum gates are constructed with free-space optical components with negligible loss. In this work, we analyze symmetric and asymmetric partially polarizing lossy beam splitters. Using the generalized beam splitter equations, we study the effects of loss on two linear

The plasmonic functional lens can realize an efficient and functional focusing of surface plasmon polaritons (SPPs), making it have great potential in applications including nano-electron point sources, smart pixels, and particle manipulation. Here, we report for the first time a novel plasmonic functional lens constructed via a nano-dichroic element. The results show that the wavelength-selective

We propose the new, to the best of our knowledge, distributed mathematical model of dissipative soliton evolution in ultra-long fiber lasers. The model is based on a modified Ginzburg–Landau equation, has a stable analytical solution, and takes into account the saturated gain and saturable absorption. The analytical results show a good accordance with the results of numerical simulation of ultra-long

Based on the anisotropic distribution of magnetic nanoparticles within magnetic fluid under an external magnetic field, a novel, to the best of our knowledge, vector magnetic field sensor based on an orthogonal offset spliced optical fiber structure cascaded with fiber taper has been proposed. The expression of interference dip wavelength with respect to external magnetic field is formulated, and the

Owing to their high sensitivity, surface plasmon resonance (SPR)-based sensors depict broad application prospects in biochemical detection, environmental monitoring, and food safety. In this paper, an optical fiber-based SPR sensor is proposed and demonstrated for the refractive index (RI) detection of liquid samples. This sensor is composed of a multimode fiber (MMF), a no-core fiber (NCF), and another

We present the first on-sky results of the microlens ring tip-tilt sensor. This sensor uses a 3D printed microlens ring feeding six multimode fibers to sense misaligned light, allowing centroid reconstruction. A tip-tilt mirror allows the beam to be corrected, increasing the amount of light coupled into a centrally positioned single-mode (science) fiber. The sensor was tested with the iLocater acquisition

A vision-based mechanical vibration measurement method is presented and verified by experiments in this paper. The coded illumination is projected on the objects by a digital light processing projector with a digital micromirror device in it. The projection patterns are designed to be concentric. In one integration time of the camera, the projector is exposed several times, which embeds temporal information