Samit Kumar Gupta

Solitary waves in parity-time (PT)–symmetric Bragg grating structure and the existence of optical rogue waves

In this work, we have studied the traveling wave solution in a nonlinear Bragg grating structure in which the core of the optical fiber is having parity-time (PT)–symmetric refractive index distribution. Below the PT-threshold, we have found a bright-solitary-wave solution for forward waves and a dark-solitary-wave solution for backward waves. The effects of increasing the traveling wave speed on the spatio-temporal evolutions of the analytical solutions have been shown and above the PT-threshold, emergence of the optical rogue waves (ORWs) has been explored based on the system parameters.

Parity–time-symmetric closed form optical quadrimer waveguides

A closed form parity–time symmetric quadrimer optical waveguide structure, reminiscent of the four-state quantum system found in quantum optics, was studied. The beam dynamics of the structure were studied numerically. The effect of inclusion of nonlinearity and dispersion was also briefly investigated and is discussed.

Peregrine rogue wave dynamics in the continuous nonlinear Schrödinger system with parity-time symmetric Kerr nonlinearity

Abstract In this work, we have studied the peregrine rogue wave dynamics, with a solitons on finite background (SFB) ansatz, in the recently proposed (Ablowitz and Musslimani, (2013) [31]) continuous nonlinear Schrodinger system with parity-time symmetric Kerr nonlinearity. We have found that the continuous nonlinear Schrodinger system with PT-symmetric nonlinearity also admits Peregrine soliton solution. Motivated by the fact that Peregrine solitons are regarded as prototypical solutions of rogue waves, we have studied Peregrine rogue wave dynamics in the c-PTNLSE model. Upon numerical computation, we observe the appearance of low-intense Kuznetsov–Ma (KM) soliton trains in the absence of transverse shift (unbroken PT-symmetry) and well-localized high-intense Peregrine rogue waves in the presence of transverse shift (broken PT-symmetry) in a definite parametric regime.

Nonlinear parity-time symmetric closed-form optical quadrimer waveguides: attractor perspective

We report a study on a closed-form nonlinear parity-time symmetric optical quadrimer waveguides system with a specific coupling scheme. The system yields power saturation behavior in the modes, which may be attributed to the inherent attractor in the system. A detailed analysis has been provided to confirm the attractor aspect of the system. This work also addresses a crucial issue regarding choice of initial conditions while carrying out numerical simulation for such systems.Graphical abstract

A string of Peregrine rogue waves in the nonlocal nonlinear Schrödinger equation with parity-time symmetric self-induced potential

Abstract Dynamic wave localization phenomena draw fundamental and technological interests in optics and photonics. Based on the recently proposed (Ablowitz and Musslimani, 2013) continuous nonlocal nonlinear Schrodinger system with parity-time symmetric Kerr nonlinearity (PTNLSE), a numerical investigation has been carried out for two first order Peregrine solitons as the initial ansatz. Peregrine soliton, as an exact solution to the PTNLSE, evokes a very potent question: what effects does the interaction of two first order Peregrine solitons have on the overall optical field dynamics. Upon numerical computation, we observe the appearance of Kuznetsov–Ma (KM) soliton trains in the unbroken PT-phase when the initial Peregrine solitons are in phase. In the out of phase condition, it shows repulsive nonlinear waves. Quite interestingly, our study shows that within a specific range of the interval factor in the transverse co-ordinate there exists a string of high intensity well-localized Peregrine rogue waves in the PT unbroken phase. We note that the interval factor as well as the transverse shift parameter play important roles in the nonlinear interaction and evolution dynamics of the optical fields. This could be important in developing fundamental understanding of nonlocal non-Hermitian NLSE systems and dynamic wave localization behaviors.

Controllable chaotic dynamics in a nonlinear fiber ring resonators with balanced gain and loss

We show the possibility of controlling the dynamical behavior of a single fiber ring resonator system with the fiber being an amplified (gain) channel and the ring being attenuated (loss) nonlinear dielectric medium. Our model is based on the simple alterations in the parity-time symmetric synthetic coupler structures proposed recently (Regensburger et al. in Nature 488:167, 2012). The system has been modeled using the transfer matrix formalism. We find that this results in a dynamically controllable algorithm for the chaotic dynamics inherent in the system. We have also shown the dependence of the period doubling point on the input amplitude, emphasizing on the dynamical aspects. Moreover, the fact that the resonator essentially plays the role of a damped harmonic oscillator has been elucidated with the nonzero intensity inside the resonator due to constant influx of input light.

Parity-time (PT)-symmetric closed-form quadrimer waveguides with focusing and defocusing nonlinearity

In the present work, a PT-symmetric closed-form quadrimer waveguides system has been considered. We observe the saturation of the optical powers in the gain-guides in nonlinear regime under the coupling scheme considered. Moreover, we also find that accumulation of optical powers in the g-r parametric space (‘g’ is the gain/loss parameter, ‘r’ nonlinearity co-efficient) in the different waveguides significantly depends on the nature (i.e. focusing or defocusing) and the strength of nonlinearity and gain/loss profile. The potential applications of this quadrimer system might be in generating high constant-power optical sources.

Periodic optical rogue waves (PORWs) in parity-time (PT) symmetric Bragg-grating structure

In this work, we present an analytical investigation of traveling wave solution in a nonlinear Bragg grating structure with the core of the optical fiber having PT-symmetric refractive index distribution. Under the approximation of weak-nonlinearity and above the PT-threshold region, the existence of highly intense, well-localized periodic train of pulses has been explored for the backward-propagating wave for some suitable choice of the parameter values of the system. The result of the present study might be useful in practical purpose in generating high-power, periodic optical pulses.