In recent years, extraordinary spin angular momenta have been investigated in a variety of structured electromagnetic waves, being of especial interest in sub-wavelength evanescent fields. Here we demonstrate analytically that, in planar and cylindrical waveguides supporting transverse electric/magnetic modes, transverse spin density arises inside the waveguide (different from the spin induced in the evanescent region outside the waveguide), carrying indeed longitudinal extraordinary (so-called) Belinfante's spin momentum. Such contribution depends linearly on the mode transverse wave vector, and is thus induced by mode confinement. Cylindrical waveguides support in addition hybrid modes that exhibit a richer phenomenology with not only azimuthal (confinement-related) spin, but also an intrinsic helicity which leads to longitudinal spin density and transverse helicity-dependent spin momentum. Results are indeed presented for configurations relevant to spin-orbit coupling in nanophotonic waveguides and to manipulating optical forces in IR-to-microwave water-filled channels. Thus guided modes intrinsically carrying confinement-induced transverse spin, combined with intrinsic-helicity-induced longitudinal spin (when hybrid), hold promise of superb devices to control spin-orbit interaction and optical forces within confined geometries throughout the electromagnetic spectra.
Radiative emission from a semi-infinite unflanged circular cylindrical dielectric waveguide or optical fiber is studied for the case of axisymmetric modes of TM polarization on the basis of an iterative scheme. The first step of the scheme leads to approximate values for the reflection coefficients and the electromagnetic fields inside and outside the waveguide. In a numerical example the reflection back into the waveguide is appreciable. Correspondingly the radiation pattern of the outgoing radiation differs appreciably from the lowest order approximation in which reflection is neglected.
We consider a plane periodical array of parallel cylindrical waveguides with evanescent coupling between them. A new method for calculating the isofrequency curves based on the multiple Mie scattering formalism (MMSF) is developed. This method is compared with the phenomenological model. The derivation of the phenomenological model by means of the MMSF is performed. The formulae for calculation of parameters of the phenomenological model are derived, such as propagation constants and coupling constants.
We derive formulas for Whispering Gallery Mode resonances and bending losses in infinite cylindrical dielectric shells and sets of concentric cylindrical shells. The formulas also apply to spherical shells and to sections of bent waveguides. The derivation is based on a WKB treatment of Helmholtz equation and can in principle be extended to any number of concentric shells. A distinctive limit analytically arises in the analysis when two shells are brought at very close distance to one another. In that limit, the two shells act as a slot waveguide. If the two shells are sufficiently apart, we i…
Optical second-harmonic generation (SHG) is studied for the confined geometry of a circular cylindrical waveguide or optical fiber. A model situation of high symmetry is considered where the material with nonlinear susceptibility is isotropic and distributed in radially symmetric manner about the axis. In addition it is assumed that the material of high second-order nonlinearity consists of a thin circular layer, with periodic variation in the axial direction - similar to a usual quasi-phasematched configuration. One can optimize the efficiency of SHG by choosing the period of the array such t…
Slow light with electromagnetically induced transparency (EIT) in the core of cylindrical waveguide (CW) for an optical fiber system containing three-level atoms is investigated. The CW modes are treated in the weakly guiding approximation which renders the analysis into manageable form. The transparency window and permittivity profile of the waveguide due to the strong pump field in the EIT scheme is calculated. For a specific permittivity profile of the waveguide due to EIT, the propagation constant of the weak signal field and spatial shape of fundamental guided mode are calculated by solvi…
Dyakonov surface waves are a well-known example of surface electromagnetic waves propagating along a plane interface between isotropic and anisotropic dielectric media. Here, we investigate the spectrum and radiative losses of Dyakonov waves at the curved interface considering both cases of "positive" and "negative" curvature of anisotropic medium. We demonstrate how Dyakonov waves at a plane interface continuously transform to the leaky or guided modes of an anisotropic cylindrical waveguide and simple derive asymptotic equation for radiative losses. All analytical results are confirmed by so…
We extend the theory of Talbot revivals for planar or rectangular geometry to the case of cylindrical waveguides. We derive a list of conditions that are necessary to obtain revivals in cylindrical waveguides. A phase space approach based on the Wigner and the Kirkwood-Rihaczek functions provides a pictorial representation of TM modes interference associated with the Talbot effect.
An electromagnetic surface wave carrying orbital angular momentum (AM) is called plasmonic vortex that also carries spin AM originating from evanescent field. In this study, spin and orbital AM of plasmonic vortex in a terahertz cylindrical corrugated waveguide (CCW) are analyzed. We report the extrinsic spin AM of the plasmonic vortex for the first time. The extrinsic spin AM is produced by the rotation of the polarization of the plasmonic vortex whose rotation axis is positioned at the vicinity of the CCW wall. The extrinsic spin AM depends on the intrinsic orbital AM and radius of CCW. The …
In this paper we demonstrate that using a mathematical physics approach (focusing the attention to the physics and using mathematics as a tool) it is possible to visualize the formation of the transverse modes inside a cylindrical waveguide. In opposition, the physical mathematics solutions (looking at the mathematical problem and then trying to impose a physical interpretation), when studying cylindrical waveguides yields to the Bessel differential equation and then it is argued that in the core are only the Bessel functions of the first kind those who describe the transverse modes. And the N…
A radial transverse resonance model for two cylindrical concentric layers with different complex dielectric constants is presented. An inverse problem with four unknowns - 3 physical material parameters and one dimensional dielectric layer thickness parameter- is solved by employing TE110 and TE210 modes with different radial field distribution. First a Newton-Raphson algorithm is used to solve a least square problem with a Lorentzian function (as resonance model and "measured" data generator). Then found resonance frequencies and quality factors are used in a second inverse Newton-Raphson alg…
Cloaking using a volumetric structure composed of stacked two-dimensional transmission-line networks is verified with measurements. The measurements are done in a waveguide, in which an array of metallic cylinders is inserted causing a short-circuit in the waveguide. The metal cylinders are cloaked using a previously designed and simulated cloak that hides the cylinders and thus enables wave propagation inside the waveguide.
Radiation processes in dielectric cylindrical waveguides
Yerevan State University（耶烈万国立大学）；Institute of Physics, Yerevan State University（耶烈万国立大学物理研究所）；Institute of Applied Problems of Physics NAS RA（亚美尼亚国家科学院应用物理问题研究所）
In this paper, we analytically study Surface Plasmon Polaritons (SPPs) in graphene-based cylindrical structures with gyroelectric layers. In the general waveguide, each graphene layer is surrounded by two various gyro-electric materials. New closed-form relations are derived for the field contributions of SPP waves. As a special case, a gyro-electric cylindrical waveguide with double-layer graphene is considered in this article. For the designed structure, the figure of merit (FOM) of 51 is reported for B= 2 T and μc=0.7 eV, at the frequency of 33 THz. It is demonstrated that the FOM of the st…
The study of metallic corrugated surfaces has recently received strong attention due to their ability to mimic the behaviour of surface plasmons. In this work, this plasmon-like behaviour is employed to design an open cylindrical waveguide. The structure consists on a longitudinally corrugated metallic cylinder with corrugations filled with a dielectric material. The dispersion relation of this waveguide is analyzed in the Òcontinuous limitÓ, defined as the limit in which the number of corrugations is infinite, but keeping their periodicity constant. It is found that, in this limit, the wavegu…
We show that waveguides with a dielectric core and a lossy metamaterial cladding (metamaterial-dielectric guides) can support hybrid ordinary-surface modes previously only known for metal-dielectric waveguides. These hybrid modes are potentially useful for frequency filtering applications as sharp changes in field attenuation occur at tailorable frequencies. Our results also show that the surface modes of a metamaterial-dielectric waveguide with comparable electric and magnetic losses can be less lossy than the surface modes of an analogous metal-dielectric waveguide with electric losses alone…
We develop a self-consistent finite element method to study spontaneous emission at nanoscale proximity of plasmonic waveguides. In the model, it is assumed that only one guided mode is dominatingly excited by the quantum emitter. With such one dominating mode assumption, the cross section of the plasmonic waveguide can be arbitrary. We apply our numerical method to calculate the coupling of a quantum emitter to a cylindrical nanowire and a rectangular waveguide, and compare the cylindrical nanowire to previous work valid in quasistatic approximation. The fraction of the energy coupled to the …
Metamaterial is promising for enhancing the capability of plasmonic devices. We consider a cylindrical waveguide with three-level Λ atoms embedded in the dielectric core. By comparing metal cladding vs metamaterial cladding of a waveguide with Λ atoms in the core, we show that, for a fixed amount of slowing of light due to electromagnetically induced transparency, the metamaterial cladding outperforms in terms of the inherent loss.
Spin and orbital angular momenta (AM) of light are well studied for free-space electromagnetic fields, even nonparaxial. One of the important applications of these concepts is the information transfer using AM modes, often via optical fibers and other guiding systems. However, the self-consistent description of the spin and orbital AM of light in optical media (including dispersive and metallic cases) was provided only recently [K.Y. Bliokh et al., Phys. Rev. Lett. 119, 073901 (2017)]. Here we present the first accurate calculations, both analytical and numerical, of the spin and orbital AM, a…
In this work we demonstrate the existence of orbital angular momentum (OAM) bright and dark supermodes in a three-evanescently coupled cylindrical waveguides system. Bright and dark supermodes are characterized by their coupling and decoupling from one of the waveguides, respectively. In addition, we demonstrate that complex couplings between modes of different waveguides appear naturally due to the characteristic spiral phase-front of OAM modes in two-dimensional configurations where the waveguides are arranged forming a triangle. Finally, by adding dissipation to the waveguide uncoupled to t…
We design a plasmonic fiber waveguide (PFW) composed of coaxial cylindrical metal-dielectric multilayers in nanoscale, and constitute the corresponding dynamical equations describing the modes of propagation in the PFW with the Kerr nonlinearity in the dielectric layers. The physics is connected to the discrete matrix nonlinear Schrödinger equations, from which the highly confined ring-like solitons in scale of subwavelength are found both for the visible light and the near-infrared light in the self-defocusing condition. Moreover, the confinement could be further improved when increasing the …
It is shown that the vector-vortex Laguerre-Gauss modes with polarization-orbital angular momentum (OAM) entanglement are the vector solutions of the Maxwell equations in a graded-index medium. Focusing of linearly and circularly polarized vortex light beams with nonzero azimuthal and radial indices in a cylindrical graded-index medium is investigated. The wave shape variation with distance taking into account the spin-orbit and nonparaxial effects is analyzed. Effect of long-term periodical revival of wave packets due to mode interference in a graded-index cylindrical optical waveguide is dem…
We propose using the effective spin-orbit interaction of light in Bragg-modulated cylindrical waveguides for the effcient separation of spin-up and spin-down photons emitted by a single photon emitter. Due to the spin and directional dependence of photonic stopbands in the waveguides, spin-up (down) photon propagation in the negative (positive) direction along the waveguide axis is blocked while the same photon freely propagates in the opposite direction.
Modern physics is largely devoted to study conservation laws, such as charge, energy, linear momentum or angular momentum, because they give us information about the symmetries of our universe. Here, we propose to add the relationship between electromagnetic duality and helicity to the toolkit. Generalized electromagnetic duality symmetry, broken in the microscopic Maxwell's equations by the empirical absence of magnetic charges, can be restored for the macroscopic Maxwell's equations. The restoration of this symmetry is shown to be independent of the geometry of the problem. These results pro…
Tightly confined plasmon waveguide modes supported by semicircular cross section top silver nanoridges are investigated in this paper. Mode field profiles, dispersion curves, propagation distances, confinement factors, and figure-of-merits of semicircular top silver nanoridge plasmon waveguide mode are calculated for different radii of curvature at different wavelengths. It is found that semicircular top silver nanoridges support tightly confined quasi-TEM plasmon waveguide modes. Semicircular top silver nanoridge mode has longer propagation distance and higher figure-of-merit than that of the…
Exact solutions are obtained for all the modes of wave propagation along an anisotropic cylindrical waveguide. Closed-form expressions for the energy flow on the waveguide are also derived. For extremely anisotropic waveguide where the transverse permittivity is negative while the longitudinal permittivity is positive, only transverse magnetic (TM) and hybrid modes will propagate on the waveguide. At any given frequency the waveguide supports an infinite number of eigenmodes. Among the TM modes, at most only one mode is forward wave. The rest of them are backward waves which can have very larg…
We develop a systematic method for deriving a quantum optical multi-mode Hamiltonian for the interaction of photons and phonons in nanophotonic dielectric materials by applying perturbation theory to the electromagnetic Hamiltonian. The Hamiltonian covers radiation pressure and electrostrictive interactions on equal footing. As a paradigmatic example, we apply our method to a cylindrical nanoscale waveguide, and derive a Hamiltonian description of Brillouin quantum optomechanics. We show analytically that in nanoscale waveguides radiation pressure dominates over electrostriction, in agreement …
We theoretically analyze the waveguide regime of light propagation in a cylindrical pore of a polymer matrix filled with liquid crystals assuming that the effective radial optical anisotropy is biaxial. From numerical analysis of the dispersion relations, the waveguide modes are found to be sensitive to the field-induced changes of the anisotropy. The electro-optic properties of the polymer porous polyethylene terephthalate (PET) films filled with the nematic liquid crystal 5CB are studied experimentally and the experimental results are compared with the results of the theoretical investigatio…
Internal physical structure can drastically modify the properties of waveguides: photonic crystal fibers are able to confine light inside a hollow air core by Bragg scattering from a periodic array of holes, while metamaterial loaded waveguides for microwaves can support propagation at frequencies well below cutoff. Anisotropic metamaterials assembled into cylindrically symmetric geometries constitute light-guiding structures that support new kinds of exotic modes. A microtube of anodized nanoporous alumina, with nanopores radially emanating from the inner wall to the outer surface, is a manif…
Reducing the bending radius of low-index contrast waveguides is essential in reducing the size of the integrated optical components. A polymeric multimode waveguide bend is presented based on the Eaton lens. The ray-tracing calculations are utilized to truncate the Eaton lens in order to improve the performance of the bend. The truncation of the lens decreases the footprint of the bend as well. The designed waveguide bend with a radius of 18.4 $μm$ is implemented by concentric cylindrical multilayer structure. The average bend losses of 0.69 and 0.87 dB are achieved for the $TM_0$ and $TM_1$ m…
Metamaterials, which are materials engineered to possess novel optical properties, have been increasingly studied. The ability to fabricate metamaterials has sparked an interest in determining possible applications. We investigate using a metamaterial for boundary engineering in waveguides. A metamaterial-clad cylindrical waveguide is used to provide confinement for an optical signal, thereby increasing the local electromagnetic energy density. We show that metamaterial-clad waveguides have unique optical properties, including new modes, which we call hybrid modes. These modes have properties …
As any physical object, light undergoing a circular trajectory features a constant extrinsic angular momentum. Within strong curvatures, this angular momentum can match the spin momentum of a photon, thus providing the opportunity of a strong spin-orbit interaction. Using this effect, we demonstrate tunable symmetry breaking in the coupling of light in a curved nanoscale plasmonic waveguide. The helicity of the impinging optical wave controls the power distribution between the two counter-propagating guided modes, including unidirectional waveguiding. We found that up to 95 % of the incoupled …
We analyse the influence of Earth's rotation (both around its own axis and around the Sun) on the propagation of light in optical media. This is done using both geometrical optics and a perturbative calculation based on Maxwell's equations in rotating coordinates in flat spacetime. Considering light propagation in cylindrical step-index waveguides in particular, the first order correction to electromagnetic modes is computed. The calculation shows that Earth's rotation causes a weak mode coupling, giving rise to sidebands, whose amplitudes are computed as well. The correction to the dispersion…
We measure the local near-field spin in topological edge state waveguides that emulate the quantum spin Hall effect. We reveal a highly structured spin density distribution that is not linked to a unique pseudospin value. From experimental near-field real-space maps and numerical calculations, we confirm that this local structure is essential in understanding the properties of optical edge states and light-matter interactions. The global spin is reduced by a factor of 30 in the near field and, for certain frequencies, flipped compared to the pseudospin measured in the far-field. We experimenta…
We propose the use of a silicon-core optical fiber for terahertz (THz) waveguide applications. Finite-difference time-domain simulations have been performed based on a cylindrical waveguide with a silicon core and silica cladding. High-resistivity silicon has a flat dispersion over a 0.1 - 3 THz range, making it viable for propagation of tunable narrowband CW THz and possibly broadband picosecond pules of THz radiation. Simulations show the propagation dynamics and the integrated intensity, from which transverse mode profiles and absorption lengths are extraced. It is found that for 140 - 250 …
This paper presents theory and finite-difference time-domain (FDTD) calculations for a single and arrays of sub-wavelength cylindrical holes in metallic films presenting large transmission. These calculations are in excellent agreement with experimental measurements. This effect has to be understood in terms of the properties exhibited by the dielectric constant of metals which cannot be treated as ideal metals for the purpose of transmission and diffraction of light. We discuss the cases of well-differentiated metals silver and tungsten. It is found that the effect of surface plasmons or othe…
We show that the orbital angular momentum (OAM) of a light field can be thermalized in a nonlinear cylindrical multimode optical waveguide. We find, that upon thermal equilibrium, the maximization of the optical entropy leads to a generalized Rayleigh-Jeans distribution that governs the power modal occupancies with respect to the discrete OAM charge numbers. This distribution is characterized by a temperature that is by nature different from that associated with the longitudinal electromagnetic momentum flow of the optical field. Counterintuitively and in contrast to previous results, we demon…
We study the enhancement of cooperativity in the atom-light interface near a nanophotonic waveguide for application to quantum nondemolition (QND) measurement of atomic spins. Here the cooperativity per atom is determined by the ratio between the measurement strength and the decoherence rate. Counterintuitively, we find that by placing the atoms at an azimuthal position where the guided probe mode has the lowest intensity, we increase the cooperativity. This arises because the QND measurement strength depends on the interference between the probe and scattered light guided into an orthogonal p…
We consider eigenmodes of a ring resonator made of a circular dielectric waveguide. Taking into account the polarization corrections, which are responsible for the interaction of polarization and orbital properties of electromagnetic waves (spin-orbit interaction of photons), results in fine splitting of the levels of scalar approximation. The basic features of this fine structure of the levels are similar to that of electron levels in an atom. Namely: 1) sublevels of the fine structure are defined by an additional quantum number: product of helicity of the wave and its orbital moment; 2) for …
