Effect Of Waveguide Dispersion 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.

Impulse Amplification in a Traveling-Wave Tube—I: Simulation and Experimental Validation

This paper presents a new one-dimensional time-domain model to be used in the analysis of the pulse response of the helix traveling-wave tube (TWT). It incorporates a novel method of implementing the effects of waveguide dispersion in one dimension. This new model has been successfully compared to an established frequency-domain model, and both time- and frequency-domain models have been compared to the impulse response of an experimental TWT. This comparison illustrates the efficacy of this new time-domain model.

Accurate three-dimensional modal solutions for optical resonators with periodic layered structure by using the finite element method

Accurate vector finite element solutions for three-dimensional (3-D) axisymmetric multilayered optical cavities are presented. Resonating wavelength and field profiles are shown for the fundamental and higher order modes for different types of optical cavities. The work has shown that for a narrow multilayered cylinder of diameter /spl les/0.5 /spl mu/m, for miniature vertical cavity surface emitting lasers (VCSEL), which is a popular class of laser showing favorable performance characteristics, the effect of waveguide dispersion is an important factor. This causes a blue shift of the output wavelength, requiring an adjustment to the layer thickness in the system design, to achieve the desired wavelength. The results of the simulation show close agreement with features obtained through experimental investigations.

FDTD microcavity simulations: design and experimental realization of waveguide-coupled single-mode ring and whispering-gallery-mode disk resonators

We investigate the properties of high-Q, wide free-spectral-range semiconductor microcavity ring and disk resonators coupled to submicron-width waveguides. Key optical design parameters are characterized using finite-difference time-domain (FDTD) solutions of the full-wave Maxwell's equations. We report coupling efficiencies and resonant frequencies that include the effects of waveguide dispersion and bending and scattering losses. For diameters of 5 /spl mu/m, the microcavity resonators can have Q's in the several thousands and a free spectral range of 6 THz (50 nm) in the 1.55 /spl mu/m, wavelength range. Studies of the transmittance characteristics illustrate the transition from single-mode resonances to whispering-gallery-mode resonances as the waveguide width of the microring is increased to form a solid microdisk. We present nanofabrication results and experimentally measured transmission resonances of AlGaAs/GaAs microcavity resonators designed in part with this method.

Complete Phase-Strain Model for Structurally Embedded Interferometric Optical Fiber Sensors

The relation between a three-dimensional state of strain and the optical phase retardation in a single mode optical fiber is formalized by drawing together classical three-dimensional crystal optics and classical waveguide theory. Neumann's strain optic relations are described in a form usable in optical fiber sensor design. These relations are then combined with weakly guiding fiber theory to develop an integral which relates the optical phase shift in a structurally embedded interferometric optical fiber strain sensor to the induced three-dimensional strain field. This process leads to a previously undisclosed, additional waveguide dispersion term which contributes on the same order to the total strain induced phase retardation as does the term derived by Butter and Hocker (1978). Still, however, waveguide dispersion effects are found to be negligibly small, even in three- dimensional loading. Butter and Hocker's equation and the complete phase-strain model developed herein can give very similar results when both are applied to certain embedded sensors. This anomaly can lead to the false conclusion that Butter and Hocker's results are equally valid for any structurally embedded sensor.

Four-photon mixing and dispersion in single-mode fibers

We show that phase matching for the four-photon mixing process in a single-mode fiber depends only on the propagation constant total dispersion beta(II)(omega). Frequencies omega(s) and omega(a), for the Stokes and anti-Stokes waves must satisfy omega(s) < omega(zd) < omega(a), where omega(zd) is the frequency for which dispersion is zero; beta(II)(omega(zd)) = 0. Variations in the frequency shift Omega(omega(p)) are described for pump frequency omega(p) around omega(zd), i.e., in the region where delicate balances of material and waveguide dispersion effects are used in fiber design. We show that no new waves are created when the pump and zero-dispersion frequencies coincide, i.e., Omega(omega(zd)) = 0. Since the creation of Stokes and anti-Stokes waves is intimately related to the beta(II)(omega) versus omega curve, some interesting results are predicted for advanced design fibers.

Experimental Verification of Ultra-Wide Bandwidth Spectra in Double-Clad Single-Mode Fiber

The low-loss and low-dispersion properties of single-mode fibers make them obvious choices for wide bandwidth system applications with very long repeater spans. This brief describes the fabrication procedure and transmission properties of a double-clad single-mode fiber which is capable of wide bandwidth (greater than 100 GHz-km for laser sources with 4-nm emission bandwidths) transmission over the widest wavelength range (1.45 μm to 1.73 μm) thus far reported in the literature. This range completely covers the lowest-loss wavelength window for fused-silica optical fibers. Double-clad lightguides <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1–4</sup> were formed by using an inner cladding to form an index well between the core and a pure silica outer cladding. A computer-aided analytical procedure was used to choose the proper fiber diameter so that waveguide dispersion effects could be used to cancel material dispersion at predetermined wavelengths. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup>

Correlation between numerical predictions and measurements of single-mode fiber dispersion characteristics

Exact numerical solutions for the LP(01) propagating mode of the scalar wave equation are used to calculate propagation constants in single-mode fibers with arbitrary refractive-index profiles. The procedure is used to correlate predicted chromatic dispersion properties of single-mode fibers based on interferometrically measured profiles with direct transmission measurements vs wavelength. Resulting waveguide dispersion effects are used to design single-mode fibers that have minimum chromatic dispersion at desired wavelengths within the 1.3-1.6-microm region.

Wavelength dispersion characteristics of single-mode fibers in low-loss region

Wavelength dispersion characteristics of single-mode silica fibers in a very low-loss region, including zero dispersion wavelengths, are studied in detail using a "difference method." Wavelength dispersion of single-mode fibers is compared for fibers with same material dispersion but with different waveguide structure. Material dispersion is evaluated by extracting waveguide dispersion from experimental results. Effects of waveguide dispersion on the zero dispersion wavelength of the single-mode fiber in a longer wavelength region are clearly analyzed. Single-mode fiber design consideration is given from the wavelength dispersion point of view.

Optical Guided Wave Mode Conversion by an Acoustic Surface Wave

The experimental observation of efficient (55%) mode conversion of thin-film optical guided waves by a collinear interaction with a surface acoustic wave is reported. The effects of waveguide dispersion and finite geometry are discussed.

The effects of dispersion in linear arrays

Abstract : The effects of waveguide dispersion on the radiation pattern and directivity of series-fed, linear arrays are investigated, and an expression for the directive gain of such arrays is derived. The directivity and radiation patterns for typical arrays are presented for various values of signal bandwidths and waveguide cutoff frequencies. It is shown that the detrimental effects of dispersion on both directivity and beamwidth are substantial when the signal bandwidth is comparable to the nominal bandwidth of the array. (Author)

The effect of waveguide dispersion on VLF timing systems

It is shown that VLF timing and navigation systems, which use two or more frequencies to resolve cycle ambiguities, may be in error when the propagation mechanism is dispersive. The error arises if the difference between group and phase velocity in such cases is neglected. At 10 kHz the error on a path 10 000 km long, for a reasonable daytime model of the earth-ionosphere waveguide, may be as much as 400 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\mu</tex> s for the first-order mode. If the second-order mode is dominant as it may be at night the error will be greatly increased.