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Paradigm Shift of On-Chip Interconnects from Electrical to Optical
Published in Thomas Noulis, Noise Coupling in System-on-Chip, 2018
Swati Joshi, Amit Kumar, Brajesh Kumar Kaushik
Directional couplers are primitive component in the design of photonic devices and systems. They are based on coupled mode theory which deals with the interaction between two propagating modes in proximity with each other. A directional coupler consist of waveguides placed close to each other, as shown in Figure 14.19, so that the evanescent field of one waveguide “feels” the second waveguide and the gradual coupling of light takes place between waveguides. Coupling is mainly controlled by spacing and medium between waveguides. Full coupling of light is possible in the case of identical waveguides; otherwise, the coupling is usually partial [62]. Couplers find applications in various design such as power splitter, switches, wavelength filters, and polarization selectors.
Optical Fiber Waveguides and Couplers
Published in Robert G. Hunsperger, Photonic Devices and Systems, 2017
If two waveguides are sufficiently close such that their evanescent fields overlap, as shown in Fig. 26, light can be coupled from one waveguide into the other. Weakly coupled fiber optic couplers are described by coupled-mode theory [46,47]. The coupled-mode theory assumes that the modes of each of the two waveguides are unaffected by the presence of the other guide. The coupling only changes the amplitudes of the modes, not their propagation constants or their transverse spatial distributions. For two identical fibers such that the modes are degenerate (Δβ = 0) and only launched into guide A [A(0) = 1, B(0) = 0], A(z)=cosκzB(z)=−jsinκz
Introduction
Published in Le Nguyen Binh, Guided Wave Photonics, 2016
The principal objectives of the book thus are: (i) to describe the fundamental principles of the guiding of lightwaves in planar and circular dielectric waveguide structures; (ii) to present theoretical and numerical techniques for the design and implementation of optical waveguides and systems of optical waveguides so as to form a network of optical guided wave components; (iii) to describe the coupling phenomena of lightwaves from one waveguide to the others, thence the coupled mode theory in scalar and vectorial approaches; (iv) to present the nonlinear effects in guided wave devices and associated phenomena so that their effects in the transmission of optical signals through optical fibers can be evaluated and methods to overcome these unwanted impairments, can be developed; (v) to illustrate the design of planar rib nonlinear optical waveguides to generate optical phase conjugated signals so as to completely compensate the distorted signals; and finally (v) to describe the generation of optical amplification through parametric conversion effects and its uses in the demultiplexing of ultra-high speed OTDM signals in the optical domain.
Application of the standard coupled-mode formalism to the analysis of holey photonic crystals
Published in Journal of Modern Optics, 2019
Lidor Giladi, Elena Smith, Vladislav Shteeman, Amos A. Hardy
A new physical approach is presented for analysis of optical characteristics of holey photonic crystals (i.e. photonic devices, built on periodicity of holes in dielectric media). This class of devices encompasses the majority of photonic crystal fibres (PCF) and several kinds of modern thresholdless lasers. Our new approach is based on Standard Coupled-Mode Theory (Standard CMT), a well-known technique, which has been considered inapplicable for holey photonic devices.
Classical simulation of coherent population return in coupled optical waveguides
Published in Journal of Modern Optics, 2022
Nida Naim, Li Deng, Jun Qian, Yueping Niu, Shangqing Gong
In this section, we start by establishing a general model for the classical simulation. The two-state system for the CPR technique and the corresponding structure containing two evanescently coupled waveguides for the optical analogue are shown in Figure 1, respectively.In this figure, and w are the propagation constant and width of the waveguide. is the distance between the waveguides and , are the lengths of the two parts of the upper waveguide. In the waveguide structure, the propagation of the optical fields can then be described by the coupled-mode theory [32] where is the electric field amplitude of the wave travelling in the two waveguides. is the coupling coefficient from waveguide m (WGm) to waveguide j (WGj). Generally, unless the two waveguides are identical to each other. By further setting , the above equation can be written as in which the detuning is defined as . If we continue to perform the transformation and , we can obtain that In this equation, the coupling constant is defined as the geometrical average of the above coefficients and .
Modeling of evanescent-wave coupling between optical dielectric waveguides
Published in International Journal of Modelling and Simulation, 2019
M. Abouheaf, W. Gueaieb, A. Samra
The Coupled Mode Theory (CMT) does not take into account the cross-overlap integrals [6,14]. Thus, the modal amplitudes a(z) and b(z) satisfy the following coupled mode equations