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Register a new userTailoring $mathcal{PT}$-symmetric soliton switch
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Added by
Arjunan Govindarajan
Publication date
2018
fields
Physics
and research's language is
English
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We theoretically demonstrate soliton steering in $mathcal{PT}$-symmetric coupled nonlinear dimers. We show that if the length of the $mathcal{PT}$-symmetric system is set to $2pi$ contrary to the conventional one which operates satisfactorily well only at the half-beat coupling length, the $mathcal{PT}$ dimer remarkably yields an ideal soliton switch exhibiting almost 99.99% energy efficiency with an ultra-low critical power.
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The unique spectral behavior exhibited by a class of non-uniform Bragg periodic structures, namely chirped and apodized fiber Bragg gratings (FBGs) influenced by parity and time reversal ($mathcal{PT}$) symmetry, is presented. The interplay between the $mathcal{PT}$-symmetry and nonuniformities brings exceptional functionalities in the broken $mathcal{PT}$-symmetric phase such as wavelength selective amplification and single-mode lasing for a wide range of variations in gain-loss. We observe that the device is no more passive and it undergoes a series of transitions from asymmetric reflection to unidirectional invisibility and multi-mode amplification as a consequence of variation in the imaginary part of the strength of modulation in different apodization profiles, namely Gaussian and raised cosine, at the given value of chirping. The chirping affords bandwidth control as well as control over the magnitude of the reflected (transmitted) light. Likewise, apodization offers additional functionality in the form of suppression of uncontrolled lasing behavior in the broken $mathcal{PT}$-symmetric regime besides moderating the reflected signals outside the band edges of the spectra.
We explore the consequences of incorporating parity and time reversal ($mathcal{PT}$) symmetries on the dynamics of nonreciprocal light propagation exhibited by a class of nonuniform periodic structures known as chirped $mathcal{PT}$-symmetric fiber Bragg gratings (FBGs). The interplay among various grating parameters such as chirping, detuning, nonlinearities, and gain/loss gives rise to unique bi- and multi-stable states in the unbroken as well as broken $mathcal{PT}$-symmetric regimes. The role of chirping on the steering dynamics of the hysteresis curve is influenced by the type of nonlinearities and the nature of detuning parameter. Also, incident directions of the input light robustly impact the steering dynamics of bistable and multistable states both in the unbroken and broken $mathcal{PT}$-symmetric regimes. When the light launching direction is reversed, critical stable states are found to occur at very low intensities which opens up a new avenue for an additional way of controlling light with light. We also analyze the phenomenon of unidirectional wave transport and the reflective bi- and multi-stable characteristics at the so-called $mathcal{PT}$-symmetry breaking point.
This note examines Gross-Pitaevskii equations with PT-symmetric potentials of the Wadati type: $V=-W^2+iW_x$. We formulate a recipe for the construction of Wadati potentials supporting exact localised solutions. The general procedure is exemplified by equations with attractive and repulsive cubic nonlinearity bearing a variety of bright and dark solitons.
We construct exact localised solutions of the PT-symmetric Gross-Pitaevskii equation with an attractive cubic nonlinearity. The trapping potential has the form of two $delta$-function wells, where one well loses particles while the other one is fed with atoms at an equal rate. The parameters of the constructed solutions are expressible in terms of the roots of a system of two transcendental algebraic equations. We also furnish a simple analytical treatment of the linear Schrodinger equation with the PT-symmetric double-$delta$ potential.
We report the role of $mathcal{PT}$-symmetry in switching characteristics of a highly nonlinear fiber Bragg grating (FBG) with cubic-quintic-septic nonlinearities. We demonstrate that the device shows novel bi-(multi-) stable states in the broken regime as a direct consequence of the shift in the photonic band gap influenced by both $mathcal{PT}$-symmetry and higher-order nonlinearities. We also numerically depict that such FBGs provide a productive test bed where the broken $mathcal{PT}$-symmetric regime can be exploited to set up all-optical applications such as binary switches, multi-level signal processing and optical computing. Unlike optical bistability (OB) in the traditional and unbroken $mathcal{PT}$-symmetric FBG, it exhibits many peculiar features such as flat-top stable states and ramp like input-output characteristics before the onset of OB phenomenon in the broken regime. The gain/loss parameter plays a dual role in controlling the switching intensities between the stable states which is facilitated by reversing the direction of light incidence. We also find that the gain/loss parameter tailors the formation of gap solitons pertaining to transmission resonances which clearly indicates that it can be employed to set up optical storage devices. Moreover, the interplay between gain/loss and higher order nonlinearities brings notable changes in the nonlinear reflection spectra of the system under constant pump powers. The influence of each control parameters on the switching operation is also presented in a nutshell to validate that FBG offers more degrees of freedom in controlling light with light.
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