Theoretical research on localized surface plasmons (LSPs) supported by a structure formed by two parallel dielectric wires with a circular cross section wrapped with a graphene sheet has an impact in the practical realm. Here, LSPs are represented in the form of an infinite series of cylindrical multipole partial waves linked to each of the graphene wires. To obtain the kinematics (complex eigenfrequencies)

Highly Er/Yb co-doped phosphosilicate fibers with low optical losses were fabricated by the MCVD method, utilizing an all-gas-phase deposition technique developed “in house.” Important characteristics such as photodarkening and photosensitivity of these fibers were thoroughly investigated. An almost negligible impact of photodarkening-induced losses (no more than 1 dB/m) was discovered in the near-infrared

In this work, we discovered the possibility of greatly relaxing requirements to the speed and dynamic range of pump power variation and, thus, of reducing synchronous pumping of ytterbium (Yb)-based fiber lasers to a very simple pump modulation yielding a mode-locked pulsed output. We show that even slow (microsecond-scale) low-index ($\le\! {0.5}$) sine-wave synchronous modulation of the pump power

With its applications in science and engineering, supercontinuum (SC) generation is a phenomenon widely studied in nonlinear fiber optics. The SC spectral properties are not difficult to measure, except those related to time. Fortunately, machine learning can help predict the time behavior of various nonlinear optics phenomena using spectral characteristics. In this study, supervised machine learning

A novel plasmonic sensor based on a photonic crystal fiber has been fabricated. Experimental results show that 2 cm is an optimal fiber length of the sensor for refractive index monitoring. It is found that the average wavelength sensitivity and the resolution of the proposed sensor are 4000 nm/RIU and ${2.5} \times {{1}}{{{0}}^{- 5}}\;{\rm{RIU}}$ in the wind range of 1.3333–1.4035, respectively. In

We report on the existence and stability of mixed-gap vector surface solitons at the interface between a uniform medium and an optical lattice with fractional-order diffraction. Two components of these vector surface solitons arise from the semi-infinite and the first finite gaps of the optical lattices, respectively. It is found that the mixed-gap vector surface solitons can be stable in the nonlinear

We theoretically investigated spectrally uncorrelated biphotons generated in a counter-propagating spontaneous parametric downconversion (CP-SPDC) from periodically poled $M{\rm TiO}X{{\rm O}_4}$ ($M = {\rm K}$, Rb, Cs; $X = {\rm P}$, As) crystals. By numerical calculation, it was found that the five crystals from the KTP family can be used to generate heralded single photons with high spectral purity

This paper presents a theoretical analysis of the optical properties of an optical cavity with both one- and two-photon intracavity absorption loss, without saturation. The cavity two-photon absorption loss per pass is assumed to be small, but otherwise the analysis is general. Analytical results for the cavity transmission as a function of cavity parameters, linear and two-photon intracavity loss

As available spectrum gets congested by different applications, spectral efficiency can be enhanced through spectrum sharing and coexistence. In this paper, we demonstrate the idea of spectrum sharing and coexistence by using optical heterodyning as a flex-spectrum photonic RF transmitter. Flexibility was achieved by tuning the RF carrier frequency from 1–5 GHz, frequencies around two spectra from

A dual-band absorber using monolayer periodically T-shaped slot-patterned graphene at terahertz frequencies is presented. By changing the dimensions or Fermi levels of the T-shaped slot-patterned graphene, both of the two absorption bands will be adjusted. The absorber has the characteristics of polarization independence and incident angle insensitivity. Also, its complementary structure, i.e., using

Quantum analysis has been done for the traveling-wave (TW) electro-optic phase modulator in the presence of the phase noise of a radio frequency (RF) oscillator and a laser source, in which the Hamiltonian for an active section of the phase modulator system is derived. The effect of RF phase noise from the oscillator and a phase velocity mismatch (PVM) between optical photons and the RF field are included

We propose a free-space quantum secure direct communication protocol by using hyper-encoded single photons. The communication parties can securely exchange private information in a deterministic way. In this protocol, single photons are encoded simultaneously by both the polarization and spatial-mode degrees of freedom that constitute a decoherence-free space. The detrimental effect introduced by either

Microscopic response theory is used to study the linear electromagnetics of a Möbius jellium quantum wire. In the energy range of interest ($\hbar \omega \sim 1 {-} 200 \;{\rm meV}$), the wire can be considered as a Möbius band with complete transverse electron confinement (${\sim}$ one-level quantum well with width $w \sim k_F^{- 1} \ll \lambda = c/\omega$). The electronic energy eigenvalues and eigenstates

Fast and secure sharing of information is among the prime concerns of almost any communication system. While commonly used cryptographic algorithms cannot provide unconditional security, high-dimensional (HD) quantum key distribution (QKD) offers an exceptional means to this end. Here, we provide a tutorial to demonstrate that HD QKD protocols can be implemented in an effective way using optical elements

New electrostatic (or, more accurately, quasi-electrostatic or slow electric) surface waves, i.e., electrostatic Dyakonov-like surface waves, are predicted theoretically. These surface waves are localized at the interface between a metallic nanowire-based hyperbolic metamaterial and an isotropic medium and travel along the interface. Solving a modified Laplace’s equation in conjunction with the appropriate

Methylammonium lead halide (${{\rm MAPbI}_3}$) is widely used as perovskite absorber material in thin-film solar cell technology because of its eminent cell performance. Recently, formamidinium lead iodide perovskite (${{\rm FAPbI}_3}$) has received great attention because of its optimum bandgap value closer to the infrared single junction range. In this paper, a suitable combination of hole transporting

The scope of scattering theory was expanded such that a novel polychromatic partially coherent radially polarized twisted beam was, for the first time to our knowledge, introduced to investigate the scattering upon a deterministic medium. Analytical expressions were derived, and spectral changes were numerically demonstrated. Results showed that the vector scattering fields would present much more

We describe a nonlinear propagation model based on a generalized Schrödinger equation in the time domain coupled to Gaussian beam evolution through ABCD matrices that account for Kerr lensing in the spatial domain. This model is well suited to simulate propagation in mildly nonlinear systems such as multipass cells for temporal compression. It is validated against both a full $(x,y,z,t)$ numerical

We report on simultaneous sum-frequency mixing and doubling of C-band and ${\sim}{980}\;{\rm nm}$ laser sources using a single segmented periodically poled lithium niobate (PPLN) crystal in a single-pass configuration. Our theoretical analysis on the spectral outputs show that a proper design of a five-segment single PPLN crystal has potential to generate violet, blue, green, and orange wavelengths

Plasmon coupling between the dipolar localized surface plasmons of a nanoegg and the longitudinal dipolar localized surface plasmons of a nearby gold nanorod is investigated within a dipolar-quasistatic limit. This was achieved by varying the core-offset of the nanoegg for different nanorod sizes at a fixed coupling distance. With respect to the plasmon peaks of the isolated nanoegg, we studied blue

Nonlinear microscopy has evolved over the last few decades to become a powerful tool for imaging and spectroscopic applications in biological sciences. In this study, ${{\rm i}^2}{\rm PIE}$, a novel spectral phase control technique, was implemented in order to compress broad-bandwidth supercontinuum light pulses generated in an all-normal-dispersion (ANDi) photonic crystal fiber (PCF). The technique

The ${\rm ZnO} {-} {{\rm ZrO}_2}$ nanocomposites were prepared using varying concentrations of ${{\rm Ho}^{3 +}}$ ions through the solution combustion method. Zirconium butoxide and zinc nitrate were used as the precursor solutions with citric acid as a fuel. The synthesis was done at a low temperature of 80°C and then the samples calcined at 600°C for 2 h, before characterization. Rietveld refinement

An optimized H1 photonic crystal (PhC) microcavity with a high quality factor ($\!Q$), small mode volume, wide measurement range, and high sensitivity is proposed, and its possibility in spectroscopic gas sensing is theoretically demonstrated. In the proposed structure, we have taken advantage of the air holes surrounding the defect region to optimize the resonance characteristics so as to detect the

Soliton formation in a femtosecond optical parametric pumped by the second harmonic of a Yb: KGW solid-state oscillator was investigated. The intracavity group delay dispersion was positive, and the soliton condition was satisfied by introducing negative nonlinearity from cascaded quadratic nonlinearity (CQN). Controllable CQN was induced by an additional second-harmonic-generating nonlinear crystal

Chiral materials possess some unusual properties for which they have attracted tremendous interest in recent research. In this paper, we discuss the interaction of electromagnetic fields with an initially isotropic material, making it anisotropic chiral by inducing magnetoelectric cross coupling. We consider a four-level double $\Lambda$-type configuration of an atomic ensemble, which is simultaneously

A TE-pass polarizer based on multiple hybrid plasmonic waveguides (HPWs) is proposed, where the polarizer section consists of four symmetrically placed HPWs and a single-mode silicon waveguide in between. Owing to the strong polarization-dependent absorption loss of the multiple HPWs, the unwanted TM polarized light is strongly attenuated while TE polarized light passes through with little loss. In

We study the behaviors of quantum speed limit time (QSLT) of a two-level atom and non-Markovianity of an atomic ensemble described by the Dicke model. Our results show that both quantities can accurately locate the critical point of quantum phase transition between normal and super-radiant phases of the model. The numerical simulations demonstrate a rapid increase in the non-Markovianity in the super-radiant

The effects of an axial static magnetic field on surface and bulk plasmons of a cylindrical electric-gyrotropic (or $\varepsilon$-anisotropic) wire are investigated. Solving a modified Laplace’s equation in conjunction with the appropriate boundary conditions, the dispersion relations, power flows, energy densities, and group velocities are obtained for both types of modes, and some numerical solutions

We present an improvement on the signal-to-background of single-beam coherent anti-Stokes Raman scattering (SB-CARS) spectroscopy measurements for systems employing ultrafast supercontinuum sources based on all-normal dispersion photonic crystal fibers. Improvements to the signal-to-background arise in the use of a new pulse-reconstruction algorithm based on temporal ptychography, ${{\rm{i}}^2}{\rm{PIE}}$

We study ${\rm{Yb}}{:}{{\rm{Ca}}_3}{{\rm{NbGa}}_3}{{\rm{Si}}_2}{{\rm{O}}_{14}}$ (Yb:CNGS) lasers in the mode-locked regime, focusing on their self-frequency-doubling potential. We characterize the laser performance in configurations without and with phase-matching for second-harmonic generation. In the former case, the laser generates 47 fs pulses at a central wavelength of 1052 nm with an average

This paper reports on the effect of both the pulse duration and environments on the surface morphology, ablated area, ablation rate, and mechanical properties of a femtosecond laser irradiated zinc (Zn) in air and ethanol. The targets were exposed to 1000 succeeding pulses of Ti:sapphire laser (800 nm) at a fluence of ${2.5}\;{\rm{J}}\;{{\rm{cm}}^{- 2}}$ with various pulse durations ranging from 30

An investigation of the spatiotemporal dynamics of a quadruple Gaussian laser beam via plasma in the presence of an external magnetic field characterized by ponderomotive and relativistic nonlinearities is presented. The moment theory approach is used to study the second-order nonlinear differential equation analytically and numerically. The evolution of the beam width parameter determines the pulse

Terahertz (THz) radiation can be used to monitor the environment by sensing its variation of refractive index. Previous studies have shown that a THz perfect absorber with several hundred Q-factors can function as sensitive THz refractive-index sensors (THz-RISs). However, the electromagnetic field simulation of THz-RIS is currently based on the numerical methods, which are inefficient when THz-RIS

We present a nonlinear mixing study of Ince–Gaussian (IG) beams in non-collinear sum-frequency generation, completing the fundamental analysis of all three families of paraxial wave equation solutions under this nonlinear process. Through theoretical and experimental results, we consider the nonlinear mixing of even and odd IG modes, and transition between the paraxial modes by controlling the eccentricity

Exploiting the uniquely tunable optical response and the strong optical Kerr nonlinearity of a graphene sheet conjugated by the propagating leaky surface plasmons (SPs) excited on top of gold (Au) stripes, an efficient and high-speed electrically reconfigurable plasmonic tweezer is presented. It is demonstrated that using a number of electrically and optically isolated Au stripes and topped graphene

In this work, we report an experimental and numerical study of the intracavity spatial filtering in edge-emitting lasers using a chirped photonic crystal (PhC) as the filtering element in the near-field domain. We provide a comprehensive analysis of the near-field PhC filtering scheme and compare it to conventional spatial filtering using a variable width slit in the far-field domain. Using a two-dimensional

In this paper, we investigate a new, to the best of our knowledge, type of guided-mode resonance optical filter with polarization-independence at normal incidence and relatively narrow spectral linewidth in the near-infrared regime. The new optical spectral filter consists of a 2D array of silicon nanorings on silicon film on silica substrate. Using finite difference time domain (FDTD) simulations

In this paper, a periodic chain composed of a two-dimensional single-layer dielectric cylinder is studied by the Fourier series expansion method combined with the perfectly matched layer approach. The phase constant and attenuation constant of the conduction mode, the forward propagation leakage mode, and the backward propagation leakage mode are analyzed conceptually under different radii. Then, the

Silver nanogratings are anisotropic plasmonic nanostructures with potential application in optical components due to their large birefringence and dichroism. We induced linear birefringence and linear dichroism in subwavelength Ag-AgCl films by irradiating with a single low-power linearly polarized laser beam. The laser beam aligns silver nanoparticles in the direction of laser polarization and forms

We develop an angular dependent thermal emissivity model by using the directional radiation pattern of short dipole antennas randomly oriented on a surface to predict the maximally achievable equilibrium temperature of spectral selective solar light absorbers. Equilibrium temperatures of ideal spectral selective solar light absorbers are calculated with the new surface thermal emissivity model.

We propose a scheme for generation of the high-order phonon sideband spectra (HPS) and frequency comb arising from the strain-induced coupling of a nitrogen-vacancy (NV) impurity to a resonant vibrational mode of a diamond nanoresonator. The underlying nonlinear process of the nanomechanical system, due to the coupling between the NV center and an additional pump laser in a phonon nanoresonator, results

We present an experimental investigation of two-photon interference using a continuous-wave laser. Using a Mach–Zehnder interferometer, we observe two-photon coalescence and its complementary effect, Hong–Ou–Mandel interference. We also demonstrate two-photon coalescence using a Michelson interferometer. Our work paves the way for the realization of multi-photon interference in high photon loss scenarios

Polarization control of terahertz (THz) waves is highly required due to their immense practical applications. Most of the THz polarization rotators in the literature depend on the transmission or reflection from metamaterials or all-dielectric metasurfaces. There is also a lack of THz polarization handling waveguides due to the material absorption in this frequency regime. In this paper, a THz photonic

Dispersive-wave generation in higher-order ${\text{HE}_{1l}}$ modes of step-index optical fibers is studied numerically. The limits to power scaling from nonlinear intermodal couplings are investigated. It is shown that single-mode operation is possible up to power levels of a few MW, whereas both pump and dispersive-wave power distributes over several modes for higher powers, making the frequency

Structured light with isolated complex $\pi$-symmetric polarization singular topologies such as lemon, star, and monstar is experimentally generated using few-mode optical fiber (FMF). These singularities, popularly known as C-points, are generated in the fiber modal field as a result of an inherent combination of orthogonally polarized Gaussian and vortex modes, excited simultaneously in FMF and controlled

We report on a detailed investigation of two approaches to the modeling of the nonlinear polarization evolution (NPE) effect, forming part of an effective artificial saturable absorber. Comparison of scalar and hybrid models was performed on an example of an all fiber laser, generating highly chirped dissipative solitons at 1.55 µm. It was shown that distributed action of this type of saturable absorber

High-resolution strain sensing based on long, high-finesse fiber Fabry–Perot interferometers (FFPIs) has been demonstrated with a special focus on the infrasonic frequency range. A novel dual-FFPI scheme allows the large environment-induced background at low frequencies to be suppressed, permitting high strain resolution limited only by excess electronic noise. Noise-equivalent strain resolution of

Multidimensional imaging has become one of the major developing trends of combustion diagnostics, and volumetric tomography is one of those techniques that has experienced significant progress over the past decades. Numerous time-resolved modalities of volumetric tomography have been developed to image a variety of physical quantities. Due to formidable expenses associated with the high-speed cameras

The Chinese medium resolution spectral imager (MERSI) carried on the Fengyun-3C (FY-3C) satellite can realize the high-precision global measurement of the cloud, aerosol, land surface, sea surface, and low-level water vapor. The MERSI is described conceptually in this paper, and the radiometric calibrations of its thermal emission bands by the on-board blackbody (BB) were given by two different algorithms

The dynamics of the optical properties of water bulk exposed to femtosecond radiation (Ti-sapphire laser, wavelength 800 nm, intensity ${\sim}{10^{13}} {\rm W}/{{\rm cm}^2}$) was studied in the time window of $\approx 1.5\;{\rm ns}$ using a pump–probe technique. Both the refractive index and absorbance were measured by femtosecond interferometric microscopy, which allowed us to gather deconvoluting

We propose an enantioselective scheme to sort homogeneous chiral particles using optical tweezers. For a certain range of material parameters, we show that a highly focused circularly polarized laser beam traps particles of a specific chirality selected by the handedness of the trapping beam. Furthermore, by applying a transverse Stokes drag force that displaces the trapped particle off-axis, we allow

We have introduced an infrared refractive-index-based sensor operating at the infrared frequency region. In designing the sensor, we have used a metamaterial structure with unit cells composed of two metallic layers, the first involving two metallic bars and slabs, and the second containing a uniform metallic sheet. With a mechanism analogous to the theoretical blackbody absorber, the structure behaves

We proposed a magnetic metamaterial (MM) with extremely large positive and negative permeability. The MMs are structured by simple metal cavity resonators, contributing to exciting magnetic responses from toroid current, dipole current, and nearest-neighbor interactions of the cavity resonator array. When the three responses coupled with each other perfectly, a strong magnetic resonance is obtained

We derive wave equations for fifth-harmonic generation in cubic centrosymmetric crystals in direct and indirect processes when an incident electric field propagates along a cubic axis. We elucidate the dependence of fifth-harmonic fields on crystal length and polarization directions of an incident field. We also devise a method to measure elements of a fifth-order nonlinear susceptibility tensor in

Nonlinear optical phenomena in silicon such as self-focusing and multi-photon absorption are strongly dependent on the wavelength, energy, and duration of the exciting pulse, especially for wavelengths ${\gt}{{2}}\;{\rm{\unicode{x00B5}{\rm m}}}$. We investigate the sub-surface modification of silicon using ultra-short pulsed lasers at wavelengths in the range of 1950–2400 nm, at a pulse duration between

By means of finite-difference time-domain (FDTD) simulations, the stationary and dynamic responses of coupled optical microring resonators made with a material exhibiting an instantaneous Kerr nonlinearity are numerically investigated. We compare the results with the coupled-mode theory (CMT) and find good agreement. We demonstrate by integrating Maxwell’s equations that this system can show a self-pulsing

We use Maxwell’s equations to derive several models describing the interaction of the multi-mode fundamental field and its second harmonic in a ring microresonator with quadratic nonlinearity and quasi-phase-matching. We demonstrate how multi-mode three-wave mixing sums entering nonlinear polarization response can be calculated via Fourier transforms of products of the field envelopes. Quasi-phase-matching

Graphene is one the most promising two-dimensional materials for functional electromagnetic components. Harnessing graphene’s high third-order nonlinearity, a standing-wave resonant system is proposed that realizes low-power and high-conversion-efficiency degenerate four-wave mixing in the THz regime. The proposed system is analyzed in depth, using a recently developed nonlinear framework based on

The surface laser-induced damage threshold (LIDT) of ${{\rm BaGa}_4}{{\rm Se}_7}$ and ${{\rm BaGa}_2}{{\rm GeSe}_6}$ nonlinear crystals was studied at 2091 nm. Both yellow and dark yellow phases of ${{\rm BaGa}_4}{{\rm Se}_7}$ were investigated. The Ho:YAG laser generating nanosecond pulses at 2 kHz, 5 kHz, and 10 kHz was used as a radiation source. The R-on-1 procedure was applied to determine the

In this work, we studied stimulated hyper-Raman scattering in the spectral range near the second optical harmonic of a laser pump in water samples containing gas nanobubbles (bubstons). The spectrum of the hyper-Raman scattering from nanobubble-free water samples was found to differ from that of nanobubbles containing water samples. To interpret these results, we put forward a hypothesis that the detected