We propose and experimentally demonstrate a highly sensitive temperature sensor based on cascaded high birefringence fiber loop mirrors (HiBi-FLMs) with the Vernier effect. The two HiBi-FLMs have almost the same free spectrum range (FSR), which can be regarded as two scales of different periods of an optical Vernier-scale, and act as the fixed part and the sliding part, respectively. A Gauss fitting

In a single-mode-fiber probe type of interferometer, the effect of fiber coupling on the sensing performance is theoretically comprehensively investigated in order to analyze and improve the achievable sensing accuracy for nanometric sensing. In both direct and via-lens coupling schemes for the interferometer, the scale factors to deduce optical path length change from the measured phase are analytically

Gas modulation refractometry is a technique for assessment of gas refractivity, density, and pressure that, by a rapid modulation of the gas, provides a means to significantly reduce the pickup of fluctuations. Although its unique feature has previously been demonstrated, no detailed explication or analysis of this ability has yet been given. This work provides a theoretical explanation, in terms of

In a conventional atomic interferometer employing $N$ atoms, the phase sensitivity is at the standard quantum limit: $1/\sqrt N$. Under usual spin squeezing, the sensitivity is increased by lowering the quantum noise. It is also possible to increase the sensitivity by leaving the quantum noise unchanged while producing phase amplification. Here we show how to increase the sensitivity, to the Heisenberg

Many powerful imaging techniques for cold atoms are based on determining the optical density by comparing a beam image having passed through the atom cloud to a reference image taken under similar conditions with no atoms. In practice, the beam profile typically contains interference fringes whose phase is not stable between camera exposures. To reduce the error of these fringes in the computed optical

Brillouin correlation-domain techniques used for fiber optic distributed sensing have been widely studied owing to their unique feature in which the spatial resolution is not limited by the phonon lifetime, unlike with time-resolved methods. This approach can be divided into two main classes according to the scattering type, i.e., spontaneous or stimulated Brillouin scattering. In this study, we derived

A new ray tracing method for the propagation of electrical fields in inhomogeneous and weakly anisotropic media is presented. With this method, we can efficiently simulate the propagation of laser beams in solid-state laser amplifiers, which suffer from high thermal loads. As a result of this method, we can find optical compensation setups that significantly reduce the depolarization losses in high-power

In this work, we present efficient generation of a high-quality vector Bessel beam using an S-wave plate (radial/azimuth polarization converter) together with an ordinary glass axicon. We examine laser-induced modifications in glass with different pulse durations. We achieve material cracking and observe dominant crack propagation directions caused by the generated beam’s intensity asymmetry. By translating

A novel triple-band, tunable, high-efficiency, mid-infrared reflected cross-polarization converter based on a graphene metasurface is proposed and studied, which comprised a periodic ellipse graphene patch with a slit, a dielectric spacer, and a metal gold substrate. Numerical simulations indicate that the proposed converter can convert a linearly polarized wave to its cross-polarized wave at three

In this study, we propose and investigate a generalized circuit model for metasurface high-sensitivity sensors and broadband absorbers. First, we propose a terahertz tunable and polarization-independent high-sensitivity sensor based on a bulk Dirac semimetal metasurface. We compare the results of the proposed circuit model with those of full-wave simulation. In addition, we achieve the spectra of the

Solar absorbers are designed for absorbing visible, infrared, and ultraviolet frequencies. Most of the absorbers designed so far have been for absorbing visible frequencies, and there is a strong need for designing infrared absorbers and ultraviolet absorbers. We present a broadband near-infrared absorber using metamaterial gold resonators. The gold resonators are uniformly placed over the ${\rm{Si}}{{\rm{O}}_2}$

We measure the four-wave mixing efficiency of dual-frequency, 300 ns, 10 µm ${{\rm CO}_2}$ laser pulses to determine the effective nonlinear refractive index of the quadratic nonlinear crystals GaSe, ${{\rm AgGaSe}_2}$, and ZnSe relative to GaAs. The effective nonlinear refractive index of GaSe and ${{\rm AgGaSe}_2}$ does not depend on the phase-matching conditions for second-harmonic and sum-frequency

We investigate linear and nonlinear spectral singularities in the transverse electric and transverse magnetic modes of a slab laser consisting of an active planar slab sandwiched between a pair of graphene or Weyl semimetal thin sheets. The requirement of the presence of linear spectral singularities gives the laser threshold condition while the existence of nonlinear spectral singularities due to

Thermal diffusion bonding of Yb:YAG and sapphire crystals was successfully implemented for the first time, and composite active elements having a geometry of a thin disk with an undoped cap were fabricated. The composites were tested in a continuous-wave thin-disk laser scheme at up to 400 W output average power, confirming that bonding strength is sufficient to operate at high thermal load. The radiation

In this paper, the features of a multifunctional device that are realized by one-dimensional magnetized plasma photonic crystals (MPPCs) containing only the plasma regulated by the external magnetic field in an innovative quasi-periodic arrangement are studied by the transfer matrix method, which possesses the characteristics of the omnidirectional bandgap (OBG), nonreciprocity (NR), and polarization

In the last decade, the plasmonic vortex field has been studied extensively due to intriguing properties such as high field enhancement, optical singularity, and orbital angular momentum. In this work, we propose metananoslots that consist of paired orthogonal nanoslots arranged in an Archimedes spiral distribution. The metananoslots work as a plasmonic vortex lens that enables the synthesis of a highly

In this paper, we propose a new theoretical scheme for generating a macroscopic Schrödinger cat state of a mechanical oscillator in a hybrid optomechanical system where a beam of two-level atoms passes through the cavity. In the model under consideration, the cavity field couples to the macroscopic mirror through the optomechanical interaction while it couples to the atom through a generalized Jaynes–Cummings

As poor stability is the primary constraint for the commercialization of perovskite solar cells, improving stability has been the primary focus of recent research works regarding solar cells that make use of perovskite materials. Different metal oxide transport layers are being used with the aim of fabricating stable perovskite solar cells. A stable and efficient solar cell with both metal oxide transport

In this paper, a novel kind of one-dimensional (1D) photonic crystal (PC) doped with indium antimonide (InSb) is proposed, which is theoretically investigated by the transfer matrix method to create a giant lateral shift that is also called the Goos–Hänchen (GH) shift. The transmittance features of the proposed PCs are ascribed to the temperature. The influences of the incident angle on the transmittance

We present a topology optimization method for a 1D dielectric metasurface, based on a new concept: fluctuation and trend analysis for initial random conditions. The key point of the proposed optimization method is that the procedure initially generates a couple of device distributions termed fluctuation/mother and trend/father, with specific spectra that efficiently sample not the local minimum of

This work presents a study of a fully nonastigmatic design of a single-longitudinal-mode, wavelength-tunable, unidirectional alexandrite ring laser cavity and assessment of its performance compared to more complex laser design requiring astigmatism compensation. A “displaced mode” nonastigmatic laser cavity design eliminating astigmatic cavity elements is developed around an alexandrite crystal end-pumped

Coherent perfect absorption (CPA) is realized in metasurfaces composed of crossed vertical bulk Dirac semimetal (BDS) stripes and ${{\rm SiO}_2}$. Under the illumination of two counter-propagating coherent beams, the coherent absorption is continuously controlled from almost 0 (approximately ${6.2} \times {{10}^{- 5}}$) to 99.97% by changing the beams’ relative phase, which gives a modulation depth

The interference contrast in a near-field diffraction pattern can be improved using an asymmetric grating with a small grating window. However, commercial asymmetrically shaped gratings are not available. Here, we report a method that overlaps two gratings to produce an arbitrary open fraction in the combination grating. Both theoretical simulation and experimental observations of the near-field Talbot

The propagation of a laser beam through a hybrid-aligned nematic layer with a surface disclination line has been investigated. A model of the light interference has been developed to consider the scattering by the structural inhomogeneities. The analytical expression that includes the factor characterizing an exponential decrease in the light scattering has been obtained. The dependence of the intensity

We study the propagation of light pulses in an absorbing medium when the frequency of their carrier coincides with a zero of the refractive index dispersion. Although slow light and, a fortiori, fast light are not expected in such conditions, we show that both can be obtained by selecting particular phase components of the transmitted field. Analytical expressions of the resulting signals are obtained

Experimental studies of the optical properties of compressible, viscous, and rapidly rotating gas flows (vortices) are presented. Gas vortices can function as optical elements such as lenses or waveguides. The optical properties are determined from direct interferometric phase measurements and beam propagation analysis. Output beams are analyzed in terms of Zernike polynomials for a range of gas flow

The observed output of an interferometer is the result of interference among the parts of the input light beam traveling along each possible optical path. In complex systems, writing down all these possible optical paths and computing their cumulative effect can become a difficult task. We present an intuitive graph-based method for solving this problem and calculating electric fields within an interferometric

The Wigner function is a mathematical tool that provides important information about a quantum light state, like entanglement and quantumness. For example, in a recent work it was shown the disentropy of the Wigner function using the Lambert–Tsallis ${W_q}$ function with $q = {2}$ can be used as a measure of quantumness. When the value of $q$ is non-integer, the disentropy and ${W_q}$ function have

In this paper, we study the possible realization of a classical system with quantum characteristics on the level of classical optics. Indeed, following Arrizon et al. [J. Opt. Soc. Am. A 32, 1140 (2015) [CrossRef] ], we first use quantum optics formalism to consider the propagation of two coherent states in a Kerr medium where the interaction between the two states is described by the cross-Kerr interaction

Frequency nondegenerate entangled photon pairs have been employed in quantum communication, imaging, and sensing. To characterize quantum entangled states with long-wavelength [infrared (IR) or even terahertz (THz)] photons, one needs to either develop the single-photon detectors at the corresponding wavelengths or use a novel tomography technique that does not rely on single-photon detections, such

We describe the generation of sequences of random bits from the parity of photon counts produced by polarization measurements on a polarization-entangled state. The resulting sequences are bias free, pass the applicable tests in the NIST battery of statistical randomness tests, and are shown to be Borel normal, without the need for experimental calibration stages or postprocessing of the output. Because

We propose a scheme for the generation of counterpropagating polarization-entangled photon pairs from a periodically poled lithium niobate on insulator waveguide. The waveguide is designed to enable a special dispersion relationship between the ${{\rm TM}_{00}}$ and ${{\rm TE}_{00}}$ modes that allows two concurrent counterpropagating quasi-phase-matching type-II spontaneous parametric downconversion

In our research, terahertz frequency-domain spectroscopy based on continuous-wave and coherent detection, which offers advantages of frequency selectivity and much higher frequency resolution, is used to acquire the optical parameter of nonpolar liquid samples in a polytetrafluoroethylene (PTFE) rectangle cell. The transfer matrix method is raised to remove the oscillation generated by the Fabry–Perot

The sensitivity advantage of waveguide-enhanced Raman spectroscopy (WERS) over free-space Raman, measured by the signal-to-noise ratio, is well established for thin molecular layer sensing, which traditionally relies on confocal Raman setups. However, for bulk liquid or gas samples, WERS must be benchmarked against nonconfocal Raman configurations. We use ray tracing to calculate the power collection

We present a module that can generate periodic light patterns and change their spacing, orientation, and position. It is done by using liquid crystal cells without pixelation (in contrast to spatial light modulators). The absence of mechanical movements allows this module to be integrated in miniature (wearable) microscopic systems to improve the image resolution by using the structured illumination

Light emission from inelastic electron tunneling has been demonstrated for 40 years. The ultrafast response rate and the ultracompact footprint make it promising for high-speed miniaturized light sources. But the application of the tunnel junction is limited by extremely low external quantum efficiency due to the low proportion of inelastic tunneling electron and wave vector mismatch between surface

This paper puts forward a subwavelength grating for highly sensitive refractive index (RI) sensing. The light-coupling condition of the grating covered by the liquid to be detected is sensitive to changes in RI of the liquid. The influence of the grating period and thickness on the coupling is studied. At the large angle of incidence, it is found that the effective RI of the grating slab is varied

We study controllable Bloch oscillation and its potential applications in a one-dimensional lattice with partly phase-modulated hopping rates. Under proper conditions, such a system can be built by using a quasi-one-dimensional sawtooth lattice with Peierls phases induced by a synthetic magnetic field. The amplitude of the Bloch oscillation can be adjusted precisely and continuously by adjusting the

Optomechanical systems are known to exhibit self-sustained limit cycles once driven above the parametric instability point. This breaks down the linearized approximation and induces novel nonlinear effects such as dynamical multistability, staircase behavior, and the generation of optical high-order sideband combs (HOSCs). Here, we study the classical nonlinear dynamics of optomechanical systems. We

We derive a novel propagation equation for optical waveguides that properly accounts for two-photon absorption (TPA). We start from a simple quantum theory of nonlinear fibers allowing for TPA to be included in a straightforward fashion. The derived equation is shown to be in excellent agreement with numerical results of conventional pump-and-probe schemes and, to the best of our knowledge, is the

We systematically investigate the optical analog of the relativistic quantum Klein tunneling effect in binary waveguide arrays (BWAs) in the presence of Kerr nonlinearity where the Dirac solitons are used to construct the initial beams. The transmission coefficient of Dirac solitons obtained by direct beam propagation simulations in the low-power regime as a function of the potential step height and

A theoretical model of a tandem radiation-balanced laser is developed and applied to explore the feasibility of radiation-balanced operation. The external cavity tandem laser is composed of an optically pumped multiple quantum well InGaAs gain section that is monolithically integrated with a Yb:YLF cooling section. It is shown that performance depends critically on a number of parameters, the choice

In this paper, we propose a scheme for the multi-hop nondestructive teleportation of an arbitrary single-qudit state via channel modulation performed by one cloud node in a network. Considering the limited quantum technology of the sender, the receiver, and the ordinary intermediate nodes, we assume that there are certain cloud nodes in a quantum network equipped with quantum processing capability

Broadband terahertz radiation can be efficiently produced by mixing laser pulses of different colors in the mid-infrared (MIR) and longwave-infrared (LWIR) spectral region. In this paper, we report on a numerical investigation of ultrashort terahertz pulse generation from plasmas created in nitrogen gas by two-color laser pulses with the fundamental laser pulse wavelength between 2.15 and 15.15 µm

We numerically investigate the power and energy scaling potential of cryogenic Yb:YLF regenerative amplifiers in rod geometry. Our approach is based on solving the coupled set of equations describing thermal behavior of the material and its effect on spectroscopic properties, gain, and overall amplification. The approach is first benchmarked with earlier experimental data. By carefully analyzing the

We report phase behaviors in silicon-wire multistage delayed interferometric (MDI) wavelength-division multiplexing (WDM) optical filters on a 300-mm silicon-on-insulator (SOI) wafer. In order to achieve spectrally uniform filter response and make clear the main factor for influencing spectral shape and uniformity across the SOI wafer, we fabricated ${1} \times {4}$ channel MDI-type WDM filters as

A strip-loaded horizontal slot waveguide is used for routing the emission of a microdisk laser. The active region of the laser contains InAs/InGaAs/GaAs quantum dots operating in CW mode under optical pumping. Although the quantum dots emit in a broad range, the laser emission is single mode with $\lambda = 1290\;\text{nm}$. Atomic layer deposition is used for the fabrication of the ${\text{TiO}_2

We theoretically study the generation of orbital angular momentum (OAM) based on the four-wave mixing process in a diamond-type homogeneously broadened $^{85}{\rm Rb}$ atomic system. We use density matrix formalism at a weak field limit to explain the origin of vortex translation between different optical fields and a generated signal. We show how the singularities, which are omnipresent in the phases

In this paper, a novel one-dimensional superconducting photonic crystal exploiting the Thue–Morse arrangement is theoretically investigated by the transfer matrix method. Two transmission states are switched in utilization of ambient temperature in the case of the same structure in the terahertz regime: one is the omnidirectional photonic bandgap (OBG) characteristics in low-temperature zones (about

The temperature distribution inside a double-cladding optical fiber laser or amplifier is examined in detail. Traditionally, the quantum defect in the core is taken to be the main source of heating in an active optical fiber. However, contributions from the parasitic absorption of the signal and the pump may also play an important role, especially for low quantum defect or radiation-balanced lasers

The nonlinear refractive index dependence on the incident light polarization state has been studied for pure chloroform and chloroform solutions of aminobenziliden-1,3-indandione derivatives. Measurements were done with linearly, elliptically, and circularly polarized light using 8 ns and 30 ps pulse duration 1064 nm lasers. This allows us to separate the electronic response, molecular reorientation

The understanding of frequency-shifting loops’ (FSLs) transient response is fundamental for their implementation in microwave photonic systems. We developed a numerical model, enabling us to describe the specific dynamics of the frequency comb generated in a FSL seeded by a CW laser. The model, based on laser rate equations, predicts the temporal evolution of the power of the individual comb lines

We theoretically investigate methods of controlling pulse generation in normal-dispersion fiber optical parametric chirped-pulse amplifiers. We focus on high-energy, ultrashort pulses at wavelengths widely separated from those of the pump, and find that within this regime, a number of simple properties describe the essential phase and gain dynamics. Of primary importance are the relationships between

A short overview of the luminescence research done in Africa is presented. A summary of the number of publications, with the necessary explanation, is given to elaborate on the research done to date. Most of the research was done on phosphor materials as well as luminescence dating by using optically stimulated luminescence. Phosphor materials have several applications, which are given as examples

The second hyperpolarizability ($\gamma$) of carbon disulfide (${{\rm CS}_2}$) is measured by gas-phase electric-field-induced second-harmonic generation for laser wavelengths in the range 765–1064 nm. The observed hyperpolarizability is decomposed into electronic (${\gamma ^e}$) and vibrational (${\gamma ^v}$) contributions, and the dispersion curve for ${\gamma ^e}$ is extrapolated to the static

Recent studies have demonstrated that in a few-cycle laser pulse, a coherent Rydberg atom—an atom in a superposition of the ground and highly excited states—can generate high-order harmonic generation (HHG) spectra with high conversion efficiency and high cutoff energy, making it a potential procedure for producing attosecond pulses. In this study, we theoretically report two interesting findings that

Light–matter interaction in cold atomic ensembles is one of the central topics in modern quantum and atomic optics with important applications in various quantum technologies. The collective response of dense atomic gases under light excitation depends crucially on the spatial distribution of atoms and the geometry of the ensemble. We analyze near-resonant light transmission in two-dimensional dense

This paper demonstrates the evaluation of the radial inhomogeneity of the magnetic field of an atomic fountain clock, which affects the Ramsey interference fringe visibility. Based on the simplified inhomogeneous magnetic field model, the relationship between the fringe visibility and the inhomogeneity of the magnetic field is obtained; a magnetic field broadening limit of 70 pT for the ${^{87}{\rm

1,2-dichloroethane (${{\rm C}_2}{{\rm H}_4}{{\rm Cl}_2}$) and 1,2-dibromoethane (${{\rm C}_2}{{\rm H}_4}{{\rm Br}_2}$) show linear absorption (LA) and stimulated light scattering in response to the excitation by 820 nm 18 fs laser pulses. Using the $Z$-scan technique, with these pulses separated by 12.2 ns (much shorter than both samples’ thermal diffusivity time constants ${\tau _{\rm th}}$’s) and

We numerically demonstrate that picosecond pulse pumped supercontinuum (SC) generation in a silicon waveguide can be enhanced with the assistance of a weak continuous-wave (CW) trigger. The bandwidth of the resulting SC is greatly improved. The effects of two-photon absorption, free-carrier absorption, and free-carrier dispersion on SC generation in the silicon waveguide are studied. The optimized