Nonlinearity effect on dual photonic crystal fiber coupler for generating fully optical logic gates

Abstract

In this work, we present a numerical investigation of the asymmetric double nonlinear coupling of photonic crystal fibers in an on‐off switch to obtain fully optical logic gates. Ultra‐short pulses (100 fs) are propagated through the device in three distinct excitation power regimes, power below critical (Po = 72 kW, where Po represents the excitation power of the device), critical power (Pc = 103.5 kW, where Pc represents critical Power for which the power switching is 50% for both guides. There are cases where Po is above the critical value, there are cases that is below), and power above critical (Po = 110 kW). The pulse switching characteristics are analyzed as a function of the input power and the nonlinearity profile (β‐beta) inserted in one of the component guides. The nonlinearity profiles follow the regimes: constant, increasing and decreasing, and high order effects, such as third‐order dispersion, intrapulse Raman scattering and self‐steepening are included in the generalized Schrödinger nonlinear equation governs the pulse propagation dynamics. The results show that the proposed device can be used to obtain AND, OR, and NOT logic gate. Numerical studies were done from the coupled‐coupled equations solved using the fourth‐order Runge‐Kutta method, using MATLAB as a programming tool for solving equations. The implementation of fully optical logic gates tends to revolutionize new digital systems in the field of data storage, such as optical memory, “replacement” of electronic circuits among other applications. Optical systems have a great advantage as they are free from electromagnetic interference and have high rates of data transmission.

Inhomogeneous nonlinearity meets parity–time-symmetric Bragg structures: route to ultralow power steering and peculiar stable states

“…The notion of inhomogeneous nonlinearity is emerging as a distinct route for making alloptical devices such as switches, logic gates, and other signal processing devices [27][28][29][30][31][32][33][34][35]. As the name implies, the term inhomogeneous nonlinearity refers to the variation in the nonlinearity ( ) as a function of propagation coordinate .…”

“…In other words, the value of the nonlinear coefficient is not constant, but it varies as the light traverses through the device [ ( )]. From a theoretical standpoint, scientific works which deal with the switching dynamics of anti-directional couplers (ADCs) [31], and directional couplers (DCs) [28,29,35] with inhomogeneous nonlinear profiles are many. There seem to exist a few works dealing with the switching in a grating with inhomogeneous nonlinearity.…”

“…Compared to the conventional FBG devices with the homogeneous nonlinearities [27], gratings with varying nonlinear profiles switch at higher or lower critical intensities depending on the profile used and the value of the inhomogeneous nonlinearity parameter ( ( )). Different kinds of nonlinear profiles exist in the form of linear, Gaussian, exponential, logarithmic, and so forth [28,29,31,34,35]. Judicious selection of the nonlinearity profile and manipulation of the inhomogeneous nonlinearity parameter are necessary for acquiring low-power AOS.…”

“…The same material with a wide range of nonlinear coefficients can be manufactured by varying the doping levels. It is possible to produce a fiber with an inhomogeneous nonlinear profile by suitably controlling the thickness, the density of the dopant, or dopant diffusion time [28,29,31,34,35]. Controlling of these parameters independently produces inhomogeneity in the linear RI profile ( 0 ).…”

“…(1), it is clear that the material should have high/low linear RI, large (small) bond length, or small (large) Sellmeier gap, to exhibit large (small) value of nonlinear coefficient ( 2 ). Thus, it is possible to fabricate fiber that support inhomogeneous nonlinearity via variable metal doping [28,29,31,34,35].…”

“…In other words, the value of the nonlinear coefficient is not constant, but it varies as the light traverses through the device [ ( )]. From a theoretical standpoint, scientific works which deal with the switching dynamics of anti-directional couplers (ADCs) [31], and directional couplers (DCs) [28,29,35] with inhomogeneous nonlinear profiles are many. There seem to exist a few works dealing with the switching in a grating with inhomogeneous nonlinearity.…”

“…Compared to the conventional FBG devices with the homogeneous nonlinearities [27], gratings with varying nonlinear profiles switch at higher or lower critical intensities depending on the profile used and the value of the inhomogeneous nonlinearity parameter ( ( )). Different kinds of nonlinear profiles exist in the form of linear, Gaussian, exponential, logarithmic, and so forth [28,29,31,34,35]. Judicious selection of the nonlinearity profile and manipulation of the inhomogeneous nonlinearity parameter are necessary for acquiring low-power AOS.…”

“…The same material with a wide range of nonlinear coefficients can be manufactured by varying the doping levels. It is possible to produce a fiber with an inhomogeneous nonlinear profile by suitably controlling the thickness, the density of the dopant, or dopant diffusion time [28,29,31,34,35]. Controlling of these parameters independently produces inhomogeneity in the linear RI profile ( 0 ).…”

“…(1), it is clear that the material should have high/low linear RI, large (small) bond length, or small (large) Sellmeier gap, to exhibit large (small) value of nonlinear coefficient ( 2 ). Thus, it is possible to fabricate fiber that support inhomogeneous nonlinearity via variable metal doping [28,29,31,34,35].…”