Dimensional Waveguide Research Articles

Efficient generation of polarization-entangled photons in metal-organic framework waveguides.

Parametric nonlinear optical processes are instrumental in optical quantum technology for generating entangled light. However, the range of materials conventionally used for producing entangled photons is limited. Metal-organic frameworks (MOFs) have emerged as a novel class of optical materials with customizable nonlinear properties and proven chemical and optical stability. The large number of combinations of metal atoms and organic ligand from which bulk MOF crystals are known to form, facilitates the search of promising candidates for nonlinear optics. To accelerate the discovery of next-generation quantum light sources, we employ a multi-scale modeling approach to study phase-matching conditions for collinear degenerate type-II spontaneous parametric down conversion (SPDC) with MOF-based one dimensional waveguides. Using periodic-density-functional theory calculations to compute the nonlinear optical properties of selected zinc-based MOF crystals, we predict polarization-entangled pair generation rates of order 104 - 107 s-1mW-1 at 1064 nm for 10 mm crystals, improving the brightness of industry materials such as PPKTP and BBO in some cases. This work underscores the great potential of MOF single crystals as entangled light sources for applications in quantum communication and sensing.

Corrugated waveguide with matched phase and group velocities: an extended regime of wave-beam interaction.

We show that it is possible to design corrugated waveguides where phase and group velocities coincide at an inflection point of the dispersion relation, thereby allowing an extended regime of interaction with a charge particle beam. This provides a basis for designing travelling slow-wave structures with a broadband interaction between relativistic charged particle beams and propagating terahertz waves allowing an energy exchange between beam and wave, amplifying terahertz radiation. We employ Fourier-Mathieu expansion, which gives approximate analytic solutions to Maxwell equations in a corrugated waveguide with periodically undulating cross-section. Being analytic, this enables quick design of corrugated waveguides, determined from desirable dispersion relations. We design a three dimensional waveguide with the desired dispersion and confirm the analytical predictions of the wave profile, using numerical simulations. Madey's theorem is used to analyse the strength of the wave-beam interaction, showing that there is a broad frequency interaction region.

Polar compactons and solitons in a two dimensional optical waveguide: Theory and simulations

The propagation of optical cylindrical compactons and solitons in a two dimensional nonlocal nonlinear waveguide is deeply investigated by carrying a particular emphasis on its nonlinear response function. Considering the weakly nonlocal medium, the two dimensional nonlocal nonlinear Schrödinger equation describing the propagation of signal light is derived. This equation contains the basic nonlinear Schrödinger equation with additional nonlinear terms proportional to the second order space derivative of coordinates in the transverse directions. By seeking the solution in polar form, this equation is separated into real and imaginary parts, followed by the analysis of the equilibrium points and their stability, predicting the type of solutions. These solutions are found both with linear and nonlinear phases through direct integration. In order to seek polar solutions, the nonlocal nonlinear Schrödinger equation is expressed in cylindrical coordinate and the resulting equation, containing additional terms inversely proportional to the radius r is not easily solvable. The type of solutions of this equation is predicted by the investigation of new equilibrium points and their stability. The analytical cylindrical compactons and pulse solitons as solutions of this equation are provided by using the Rayleigh–Ritz variational method, usually used for symmetric radial solitons to approximate pulse solitons in polar coordinate, and the stability of these solutions is checked through numerical investigations.

Flower-shape resonator-based triple-band metamaterial wave absorbers to find the dispersion relation utilizing one dimensional (1-D) periodic waveguide

This paper proposes a flower-shape resonator-based triple band with a high-performance metamaterial wave absorber to find the dispersion relation utilizing one dimensional (1-D) periodic waveguide. The proposed absorber comprises flower-shaped square split ring resonator-based resonators separated by a Rogers RT5870 (lossy) dielectric layer with a thickness of 1.575 mm and back annealed copper with 0.035 mm thickness, and the size of the unit cell is 8 mm × 8 mm. The outcomes of simulations conducted using the Computer Simulator Technology (CST) Microwave Studio simulator reveal the presence of three absorption peaks at frequencies of 5.032, 7.96, and 13.94 GHz with an absorption of 99.709%, 99.966%, and 99.973%, respectively. As a result, this work presents a substitute concept in terms of phase velocity of mode in limited with periodic arrangements, showing it determines the type with terms of modalities a one-dimensional periodic concave parallel plates wavelength. The suggested phase velocity has been analysed using simulations using the CST Microwave Studio simulator and the CST eigenmode solver. A comparable circuit analysis demonstrates the superior performance of the metamaterial wave absorber, indicating its potential for excellent functionality within the advanced design system (ADS) software. Additionally, the proposed structures, modelled with the High-Frequency Structure Simulator (HFSS), exhibit a close correspondence with the maximum absorbance observed at each resonance peak in CST simulation results. The proposed research demonstrates excellent features such as unity absorption, angle insensitivity, and more, making it highly suitable for dispersion relation as well as C, X, and Ku band applications.

Designer quantum states on a fractal substrate: Compact localization, flat bands and the edge modes

Compact localized single particle eigenstates on a deterministic fractal substrate, modelled by a triangular Sierpinski gasket of arbitrarily large size, are unravelled and examined analytically. We prescribe an exact real space renormalization group (RSRG) decimation scheme within a tight binding formalism to discern these states, and argue that the number of such states can be infinite if the fractal substrate is enlarged to its thermodynamic limit. Interestingly, these localized states turn out to populate the non-dispersive, flat bands in a periodic array of Sierpinski gasket motifs, however large they may be. Our results match and corroborate the recently observed compact localized, flat band states engineered on two dimensional photonic waveguide networks with a fractal geometry, and provide a whole subset of them, which, in principle, should be observable in fractal photonic lattice experiments.

Low-loss 3-dimensional waveguide crossing with a parabolic taper interlayer coupler based on a SiN-SiN-Si three-layer platform.

We demonstrated a SiN-SiN-Si three-layer silicon waveguide crossing with low-loss crossings and interlayer couplers. The underpass and overpass crossings exhibited ultralow loss (<0.82/1.16 mdB) and cross talk (<-56/-48 dB) in the wavelength range of 1260-1340 nm. To reduce the loss and length of the interlayer coupler, a parabolic interlayer coupling structure was adopted. The measured interlayer coupling loss was less than 0.11 dB from 1260 to 1340 nm, which is, to the best of our knowledge, the lowest loss reported for an interlayer coupler based on a SiN-SiN-Si three-layer platform. The total interlayer coupler length was only 120 µm.

Floquet engineering of two dimensional photonic waveguide arrays with [formula omitted] or [formula omitted] corner states

In this paper, we theoretically study the Floquet engineering of two dimensional photonic waveguide arrays in three types of lattices: honeycomb lattice with Kekulé distortion, breathing square lattice and breathing Kagome lattice. The Kekulé distortion factor or the breathing factor in the corresponding lattice is periodically changed along the axial direction of the photonic waveguide with frequency ω. Within certain ranges of ω, the Floquet corner states in the Floquet band gap of quasi-energy spectrum are found, which are localized at the corner of the finite two-dimensional arrays. Due to particle-hole symmetry in the model of honeycomb and square lattice, the quasi-energy level of the Floquet π corner states is ±ω/2. On the other hand, Kagome lattice does not have particle-hole symmetry, so that the quasi-energy level of the Floquet ±2π/3 corner states is near to ±1ω/3. The corner states are either protected by crystalline symmetry or reflection symmetry. The finding of Floquet fractional-π corner states could provide more options for engineering of on-chip photonic devices.

Electromagnetic Filtering with High Performance by one Dimensional Defective Comb-Like Waveguides Structure Using the Transfer Matrix

In this paper, we study the propagation of electromagnetic waves in 1D photonic comb-like waveguides (CWGs) structure. This CWGs structure is constituted by a periodicity of segments of length d1 and grafted in each site by one resonator of length d2. This system creates the pass bands separated by large photonic band gaps where the electromagnetic waves cannot propagate. Our study focuses on the impact of a geometrical defect on the transmission spectrum. The creation of a defect of length d02 at the resonator in a perfect structure makes it possible to identify localized modes (defect modes) in the bandgaps. In this research, we demonstrate that a single defect at the resonator can lead to the filtering of two or more frequencies. The analytical calculation is performed using the transfer matrix method. This method aims to calculate the dispersion relation and the transmission rate. This structure has potential applications as an electromagnetic guiding, filtering and demultiplexing.

A proposal for a Giga Pascal pressure sensor using one dimensional photonic waveguide at 850 /1310/1550 nm signal

A proposal for a Giga Pascal pressure sensor using one dimensional photonic waveguide at 850 /1310/1550 nm signal

Cylindrical Compactons and Short Pulses in a Two Dimensional Optical Waveguide: Theory and Simulations

Cylindrical Compactons and Short Pulses in a Two Dimensional Optical Waveguide: Theory and Simulations

Airy–Gaussian vortex beams in the fractional nonlinear-Schrödinger medium

We address the propagation of vortex beams with the circular Airy–Gaussian shape in a ( 2 + 1 )-dimensional optical waveguide modeled by the fractional nonlinear Schrödinger equation. Systematic analysis of autofocusing of the beams reveals a strongly non-monotonous dependence of peak intensity in the focal plane on the corresponding Lévy index α , with a strong maximum at α ∼ 1.4 . Effects of the nonlinearity strength, the ratio of widths of the Airy and Gaussian factors in the input, as well as the beams’ vorticity on the autofocusing dynamics are explored. In particular, multiple autofocusing events occur if the nonlinearity is strong enough. Under the action of azimuthal modulational instability, an axisymmetric beam may split into a set of separating bright spots. In the case of strong fractality (for α close to one), the nonlinear beams self-trap, after the first instance of autofocusing, into a breathing vortical quasi-soliton. Radiation forces induced by the beams’ field are considered too, and a capture position for a probe nanoparticle is thus identified.

Coherent single-photon scattering spectra for a giant-atom waveguide-QED system beyond the dipole approximation

We investigate the single-photon scattering spectra of a giant atom coupled to a one dimensional waveguide via multiple connection points or a continuous coupling region. Using a full quantum mechanical method, we obtain the general analytic expressions for the single-photon scattering coefficients, which are valid in both the Markovian and the non-arkovian regimes. We summarize the influences of the non-dipole effects, mainly caused by the phases accumulated by photons traveling between coupling points, on the scattering spectra. We find that under the Markovian limit, the phase decay is detuning-independent, resulting in Lorentzian lineshapes characterized by the Lamb shifts and the effective decay rates. While in the non-Markovian regime, the accumulated phases become detuning-dependent, giving rise to non-Lorentzian lineshapes, characterized by multiple side peaks and total transmission points. Another interesting phenomenon in the non-Markovian regime is generation of broad photonic band gap by a single giant atom. We further generalize the case of discrete coupling points to the continuum limit with atom coupling to the waveguide via a continuous area, and analyze the scattering spectra for some typical distributions of coupling strength.

All optical logic gates based on nanoplasmonic MIM waveguides

In this paper, we propose and investigate some designs of basic plasmonic logic gates in two dimensional plasmonic waveguides with nanotube metal-insulator-metal waveguides using the numerical method of eigenmode expansion. These gates, including XOR, OR, NOT, and Feynman gate can be realized by changing geometrical parameters properly. Also, by cascading and combining these basic logic gates, any complex logic function can also be obtained providing the highly integrated optical logic circuits. The proposed logic gates have the broadband up to 300 nm and only spend the compact size as much as 2 µm×1.2 µm. Thus, the devices can be applied widely and significantly in optical computing and processing devices.

On scattering for the defocusing nonlinear Schrödinger equation on waveguide [formula omitted] (when m = 2,3)

In the article, we prove the large data scattering for two models, i.e. the defocusing quintic nonlinear Schrödinger equation on R2 × T and the defocusing cubic nonlinear Schrödinger equation on R3 × T. Both of the two equations are mass supercritical and energy critical. The main ingredients of the proofs contain global Stricharz estimate, profile decomposition and energy induction method. This paper is the second project of our series work (two papers, together with [31]) on large data scattering for the defocusing critical NLS with integer index nonlinearity on low dimensional waveguides. At this point, this category of problems are almost solved except for two remaining resonant system conjectures and the quintic NLS problem on R×T.

Novel 500-GHz Band Waveguide Stepped Septum-Type Circular Polarizer with a New High-Accuracy and Very Small Waveguide Flange

A new waveguide stepped septum-type circular polarizer (SST-CP) was developed to operate in the 500-GHz band for radio astronomical and planetary atmospheric observations. In a previous study, we developed a practical SST-CP for the 230-GHz band. However, several issues prevent this device being easily scaled down to the 500-GHz band, such as manufacturing dimensional errors and waveguide flange position errors. In this study, we developed a new waveguide flange with a high-accuracy position determination mechanism and a very small size of 10 × 10 mm. We also developed a new fabrication technique to obtain very good flatness for the device’s blank materials by high-accuracy polishing using a resin fixture. Using these new methods, the manufactured 500-GHz band SST-CP achieved a cross-polarization talk level of better than – 30 dB at 465–505 GHz, a device surface flatness of within 3 μm, and also the horizontal positioning error of ± 3 μm. These results indicate that the developed 500-GHz band SST-CP has high performance in the high-frequency band, and thus the new manufacturing methods are effective in the 500-GHz band.

Dimensional confinement and waveguide effect of Dyakonov surface waves in twisted confined media

Abstract We theoretically study Dyakonov surface waveguide modes that propagate along the planar strip interfacial waveguide between two uniaxial dielectrics. We demonstrate that owing to the one-dimensional electromagnetic confinement, Dyakonov surface waveguide modes can propagate in the directions that are forbidden for the classical Dyakonov surface waves at the infinite interface. We show that this situation is similar to a waveguide effect and formulate the resonance conditions at which Dyakonov surface waveguide modes exist. We demonstrate that the propagation of such modes without losses is possible. We also consider a case of two-dimensional confinement, where the interface between two anisotropic dielectrics is bounded in both orthogonal directions. We show that such a structure supports Dyakonov surface cavity modes. Analytical results are confirmed by comparing with full-wave solutions of Maxwell’s equations. We believe that our work paves the way toward new insights in the field of surface waves in anisotropic media.

Design and optimization of Y-Junction and T-Junction splitters using photonic crystal

We proposed a high transmission Y-Junction and T-Junction 1x2 power splitters based on two Dimensional photonic crystal waveguide with lattice consisting of air holes. The 1x2 power splitters is made of silicon rods with the refractive index n 1 = 3 . 46 which are perforated in air with refractive index n 2 = 1. The defects are formed by adding additional glass rods at its bends, and by increasing rods radius nearer to the propagation path. Plane wave expansion solver method is used for calculating the photonic band gap. The Resulted optical properties are obtained by using Opti-FDTD simulation at a wavelength λ = 1900 nm, a wave which was used to calculate the Poynting vector z as well as the magnetic and electric field. The Comparison of results for Y and T-Junction shows that the T-Junction has improved Electric and Magnetic Fields better than Y-Junction.

Design of a 2D fiber mode converter using a planar 2D multi-mode interference structure

In this work, we present a new design of a fiber mode converter using a two dimensional multi-mode interference waveguide (2D MMI) Structure. The proposed structure allows the conversion of the fundamental fiber mode LP01 to the second order LP21 fiber mode in multimode fiber. The 2D MMI is used as a 1 × 4 splitter and followed by a phase shifter to construct the proper phase map of the higher order LP21 mode. The design is based on the self- imaging properties of the 2D MMI structure and can thus be generalized to higher order modes. The proposed structure shows an insertion loss of about −0.96 dB and a Wavelength Dependent Loss (WDL) of about 0.4 dB over a spectral range of 140 nm around 1550 nm.

Subradiant bound dimer excited states of emitter chains coupled to a one dimensional waveguide

This Letter shows that chains of optical or microwave emitters coupled to a 1D waveguide support subradiant states with close pairs of excited emitters, which have longer lifetimes than even the most subradiant states with only a single excitation. Exact, analytical expressions for non-radiative excitation dimer states are obtained in the limit of infinite chains. To understand the mechanism underlying these states, we present a formal equivalence between subradiant dimers and single localized excitations around a chain defect (unoccupied site). Our analytical mapping permits extension to emitter chains coupled to the 3D free space vacuum field.

Lévy flight of superdiffusive light in coupled waveguide lattices

This paper reports on exotic behavior of light in one dimensional optical waveguide lattices with selective doping. The presence of gain in such lattices reduces the critical transition distance from ballistic to diffusive domain and guides the light to propagate in super-diffusive regime after certain distance. These findings may may lead to disordered lasing and also assist in image projection/transport.