A compact footprint, low-power consumption, and high-speed operation electro-optical full-adder/full-subtractor based on graphene–silicon electro-optical switches is demonstrated. Each switch consists of a Mach–Zehnder interferometer in which few-layer graphene is embedded in a silicon slot waveguide to construct phase shifters. The presented structure can be used as full-adder and full-subtractor simultaneously. The analysis of various factors such as extinction ratio, power consumption, and operation speed has been presented. As will be shown, the proposed electro-optical switch has a minimum extinction ratio of 36.21 dB, maximum insertion loss about 0.18 dB, high operation speed of 180 GHz, and is able to work with a low applied voltage about 1.4 V. Also, the extinction ratio and insertion loss of the full-adder/full-subtractor are about 30 and 1.5 dB, respectively, for transfer electric modes at telecommunication wavelength of 1.55 μm.
Many authors simply use band structure of infinite photonic crystals to predict the beam's direction in a finite structure.
The validity of this approximation for high frequencies has been questioned by Felbacq (PRL 92, 193902) and instead a
dressed (by evanescent waves) transfer matrix has been suggested. In this work, we show through numerical examples
that the direction obtained by conventional band structure is more accurate than that of dressed transfer matrix of Felbacq
et. al. We also demonstrate that this approximation can be improved by taking the effect of evanescent Bloch modes into
consideration. The effect of these modes leads to a constant shift of beam's center inside and far enough from the PC's
interface.
A theory is presented for the quantum radiation emitted from a single exciton in a quantum dot. We assume that the
quantum dot is in strong coupling to a slab photonic crystal cavity. A dielectric function of spatial coordinates is used to
explain the effects of the macroscopic medium. It has been proved that the electric field in such a medium can be
described using the so-called K-function. We derive a formula for obtaining the frequency spectrum, and present an
analytical result for the optical spectrum, which is dependent on the K-function. We also have considered a slab photonic
crystal configuration with hexagonal structure containing a cavity to evaluate the frequency spectrum in such a medium.
FDTD method has been used to calculate the generalized-transverse green function and the K-function everywhere in the
medium.
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