Dispersion Characteristics Of Waveguides Research Articles

Waveguide dispersion effects in silicon-on-insulator coupled-resonator optical waveguides

The dispersion of the waveguides that constitute microring resonators can considerably affect the dispersion characteristics of coupled-resonator optical waveguides (CROWs). We derive expressions for CROW dispersion and group delay for silicon-on-insulator microring CROWs, showing both theoretically and experimentally the band-to-band dependence of the bandwidth and group delay on the dispersion properties of the constituent single-mode silicon waveguide.

Elastic waves in piezoceramic cylinders of sector cross-section

The propagation of elastic waves in piezoceramic cylindrical waveguides of circular cross-sections with sector cut is investigated on the basis of the linear theory of electroelasticity. Dispersion functions are obtained from boundary conditions in an analytical form of functional determinants for each value of the generalized wave number. A selected set of numerical results including real, imaginary and complex branches of full dispersion spectrums with various symmetry of wave movements is presented to describe the essential characteristics of the waves. Leading effects of spectrums transformation by change of waveguide’s angular measure are enlightened, and wave asymptotic behavior is analyzed. The variation of the cross-section is considered as a mechanism to control the dispersion characteristics of waveguides.

Study on optical waveguides based on omnidirectional reflection of two-dimensional photonic crystals

The omnidirectional reflection of two-dimensional photonic crystals and an optical wave-guiding structure based on omnidirectional reflection are presented, respectively. The dispersion and transmission characteristics of waveguides using this structure are investigated by numerical simulations using the plane wave expansion method and the finite-difference time-domain method, respectively. Numerical results indicate that, for an optimized 90° waveguide bend, a very high transmission (>98%) can also be observed. This waveguide is expected to be applied to highly dense photonic integrated circuits after further research.

Polarization-Independent Wavelength Conversion Using an Angled-Polarization Pump in a Silicon Nanowire Waveguide

A proposal for polarization-independent wavelength conversion is presented based on four-wave mixing in a silicon nanowire waveguide using an angled-polarization pump. The principle of polarization independence is introduced and the theoretical model is established. The optimized incident pump polarization angle is obtained for different waveguide geometries, and a polarization-independent bandwidth of 64 nm is achieved with the efficiency fluctuation of less than 1 dB in a 285 nm × 650 nm silicon waveguide. The polarization-independent bandwidth is limited by the larger one of the TE- and TM-mode phase mismatches, and can be enhanced further by carefully tailoring the dispersion characteristics of the silicon nanowire waveguide.

Dispersion characteristics of nanometer-scaled silicon rib waveguides

We investigate the dispersion properties of nanometer-scaled silicon waveguides with channel and rib cross section around the optical fiber communication wavelength and systematically study their relationship with the key structural parameters of the waveguide. The simulation results show that the introduction of an extra degree of freedom in the rib depth enables the rib waveguide more flexible in engineering the group velocity dispersion (GVD) compared with the channel waveguide. Besides, we get the structural parameters of the waveguides that can realize zero-GVD at 1550 nm.

Flexible optical waveguides based on the omnidirectional reflection of one-dimensional photonic crystals

An optical wave guiding structure based on the omnidirectional reflection of one-dimensional photonic crystals is presented. The dispersion and transmission characteristics of flexible waveguides using this structure are investigated by numerical simulations using plane wave expansion method and finite-difference time-domain method, respectively. Calculated results indicate that for waveguide bends of arbitrary angles with a curved radius less than several wavelengths, a very high transmission (>97%) over wide frequency range is observed. Owing to this unique advantage of flexibility, it is expected to be applied to highly dense photonic integrated circuits after further research.

Dispersion characteristics of SOI-based slot optical waveguides

The invention of the slot waveguide had enabled a number of interesting novel linear or nonlinear optical applications by guiding light in nanometers-wide low index slots guarded by high-index slabs. As one of its key characteristics, the low modal index for this kind of waveguides has been demonstrated by many studies. However, their higher order dispersion properties have not been thoroughly investigated yet, while the growing size and complexity of these devices and their potential nonlinear optical applications involving short optical pulses demand further understanding in their dispersion behavior. We here carry out a numerical study on the higher order dispersion characteristics of the SOI-based slot structures around the 1550 nm wavelength. Our results show that they could have significantly different second order dispersion properties in contrast to the traditional channel SOI waveguides. Their potentially large normal dispersion could have an impact on various nonlinear or linear applications. The relationship between the dispersion performance and the waveguide design is also investigated, and the results could show further venues to optimize or control the dispersion properties of such waveguides.

Particle filtering for dispersion curve tracking in ocean acoustics

A particle filtering method is developed for dispersion curve extraction from spectrograms of broadband acoustic signals propagating in underwater media. The goal is to obtain accurate representation of modal dispersion which can be employed for source localization and geoacoustic inversion. Results are presented from the application of the method to synthetic data, demonstrating the potential of the approach for accurate estimation of waveguide dispersion characteristics. The method outperforms simple time-frequency analysis providing estimates that are very close to numerically calculated dispersion curves. The method also provides uncertainty information on modal arrival time estimates, typically unavailable when traditional methods are used.

Features of the dispersion characteristics of nonuniform plasma waveguides in a longitudinal magnetic field

We study the features of the dispersion curves and field structures of the fundamental axisymmetric mode of nonuniform layered plasma waveguides in a longitudinal magnetic field. It is shown that the presence of sharp boundaries between layers leads to the appearance of additional branches of the dispersion curves in the frequency range ω Be < ω < ωUH(0), where ωBe is the electron gyrofrequency and ωUH(0) is the upper-hybrid resonance frequency for the near-axis region of a nonuniform waveguide. The fields of eigenmodes corresponding to these branches comprise resonance structures near the sharp plasma-density variation at which the upper-hybrid resonance conditions are satisfied and plasma waves are excited. The frequency interval of such a branch is limited by the resonant frequencies of the neighboring uniform layers. It turns out that in the case of a strong magnetic field ({ie392-01}, where ωp is the plasma frequency having the value {ie392-02} in the near-axis region of a nonuniform waveguide), the fundamental-mode field is localized in the near-axis region of a nonuniform waveguide, whereas in the opposite case {ie392-03}, the maximum wave fields are localized in either the upper-hybrid resonance region or the outer (near-boundary) layer of the waveguide if there is no resonance region. It is found that the whistler (helicon) contribution to the field structure of the fundamental axisymmetric mode is very small for narrow nonuniform waveguides (b < λ0, where b is the waveguide radius and λ0 is the wavelength in free space) if the plasma density on the axis is high compared with the cutoff density {ie392-04}. We present one of the possible explanations for the effect of narrowing of the plasma channel of a high-frequency whistler-range discharge with distance from a source in the increasing magnetic field.

A Compact 2-D Finite-Difference Frequency-Domain Method for Dispersion Characteristics Analysis of Trapezoidal-Ridge Waveguides

A compact two-dimension (2-D) finite-difference frequency-domain (FDFD) method is used to analyze the dispersion characteristics of single and double trapezoidal-ridge waveguides. The general 2-D FDFD formulation under orthogonal curvilinear coordinate system is derived from the difference form of Maxwell’s equations, and modified difference formulas at the trapezoidal-ridge section are built. After implementing the boundary conditions, the 2-D FDFD formulation is concluded as an eigen equation and then constructed by a highly sparse matrix. By solving the matrix-eigen equation, the dispersion characteristics of the ridged waveguides can be obtained. Computed results are in good agreements with the previously published and simulated ones, which prove the correctness of the method.

Increased pump acceptance bandwidth in spontaneous parametric downconversion process using Bragg reflection waveguides

In this paper we show that by suitably tailoring the dispersion characteristics of a Bragg reflection waveguide (BRW) mode, it is possible to achieve efficient photon pair generation over a large pump bandwidth while maintaining narrow signal bandwidth. The structure proposed consists of a high index core BRW with a periodically poled GaN core and periodically stratified cladding made up of alternate layers of Al(0.02)Ga(0.98)N and Al(0.45)Ga(0.55)N. Such photon-pair generators should find applications in realizing compact and stable sources for quantum information processing.

Application of 4-Component Compact 2-D FDFD Method in Analysis of Lossy Circular Metal Waveguide

A 4-component compact 2-D finite-difference frequency-domain (FDFD) method is utilized for the analysis of dispersion characteristics of lossy circular metal waveguide. In the analysis, the surface-impedance boundary condition (SIBC) can be implemented as easy as that in 6-component method in literature. The phase constant and attenuation constant can be obtained as solution of eigen value problem for a given frequency. The results agree very well with the theoretical solutions.

Higher order interactions in magneto-inductive waveguides

The properties of periodic chains of magnetically coupled L–C resonators supporting magneto-inductive (MI) waves are examined in the case when non-nearest neighbour interactions are significant. The variation of the coupling coefficient with separation is measured using resonant elements based on printed circuit board inductors and surface mount capacitors, and used to predict the S-parameters and dispersion characteristics of magnetoinductive waveguides. Good agreement with experimental measurements is obtained when higher order interactions are included. The significance of non-nearest neighbour interactions in more general MI wave devices is then highlighted in an example problem involving reflection from a waveguide discontinuity, and the influence of higher order evanescent waves is discussed.

Integrated-optic wavelength demultiplexer on lithium niobate by double proton exchange

An integrated-optic wavelength demultiplexer produced by double proton exchange on z-cut lithium niobate is demonstrated. The mode sorting effect and waveguide dispersion characteristics are utilized to demultiplex the optical fields at the wavelengths 980 nm and 1550 nm. The opposite waveguide dispersion in the two output waveguides can be obtained by designing the aspect ratio of the waveguide structure and the refractive index profile of the waveguide. The design parameters include the waveguide width, the proton-exchange time, the annealing time, and the depth of the second proton-exchanged layer. The semivectorial finite difference method is utilized to calculate the effective index of the guided mode in the output waveguide in order to obtain the required waveguide dispersion for wavelength demultiplexing. In the experiment, the effects of waveguide width, branching angle, and depth of the second proton-exchanged layer on the device performance are discussed.

Dispersion characteristics of metamaterial hollow-core cylindrical waveguides

The work deals with the study of metamaterial hollow-core cylindrical (MHC) waveguides. In the article the solution of Maxwell’s equations to analyse a MHC waveguide is presented. A dispersion equation was obtained in the form of a determinant. We created the computer algorithm in MATLAB language to investigate the dispersion properties of the MHC waveguide. The MHC waveguide was studied in the frequency range from 75 to 115 GHz with different waveguide parameters (radius, azimuthal index). We have analysed the dependences of the MHC waveguide main and higher order modes’ dispersion characteristics on a waveguide radius and an azimuthal index.

Dispersion engineering of highly nonlinear As_2S_3 waveguides for parametric gain and wavelength conversion

We numerically demonstrate the use of waveguide dispersion to shift the zero-dispersion wavelength of an As(2)S(3) waveguide to telecom wavelengths. The device implications for parametric gain and wavelength-conversion via four-wave mixing are investigated, giving an operating bandwidth of 550 nm. We also show that the photosensitivity of chalcogenide can be used for post-fabrication tuning of waveguide dispersion characteristics.

Dispersion characteristics of asymmetric double-negative material slab waveguides

The dispersion characteristics of asymmetric double-negative material slab waveguides have been investigated by using normalized parameters. The results show that the dispersion characteristics of these material waveguides differ dramatically from conventional guided waves, and they possess a number of unusual properties, including the absence of fundamental modes, propagation of the first-order mode within narrow frequency ranges, and the existence of modes for imaginary transverse wave numbers, for example. In particular, for one fast wave mode, near cutoff, one normalized frequency corresponds to two possible propagation coefficients.

An FDTD Analysis of Nonlinear Photonic Crystal Waveguides

We present a modelling technique for analyzing dispersion characteristics of nonlinear photonic crystal waveguides. This technique combines the nonlinear finite-difference time-domain method, based on the numerical simulation of oscillating dipole radiation, with the super cell approach and the periodic boundary conditions. The technique presented makes it possible to calculate the dispersion characteristics of Kerr-like nonlinear photonic crystals waveguides made by removing some scatterers. A numerical tool based on this technique can be used to design various components for integrated optical circuits.

Dispersion Characteristics of Coplanar Waveguides at Subterahertz Frequencies

We present experimental and simulated studies of the dispersion characteristics of coplanar waveguides (CPWs) at subterahertz frequencies. Two types of CPWs were studied, those with wide ground planes and those with narrow ground planes. In both cases, simulations closely followed the experimental results, thus giving us a basis for implementing the simulations in circuit-design modes for a wide range of such waveguides.

Dispersion Characteristics of Coplanar Waveguides at Subterahertz Frequencies

We present experimental and simulated studies of the dispersion characteristics of coplanar waveguides (CPWs) at subterahertz frequencies. Two types of CPWs were studied, those with wide ground planes and those with narrow ground planes. In both cases, simulations closely followed the experimental results, thus giving us a basis for implementing the simulations in circuit-design modes for a wide range of such waveguides.