Kerr-nonlinearity induced bistable-like parity-time phase transition in coupled waveguides

Abstract

We analyze the parity-time ( P T ) symmetric phase in coupled two waveguides with a Kerr-type medium in between. Paying attention to the emitted field from a dipole source inside, we show that when the strength of the dipole increases, the optical Kerr effect can render a phase transition from the exact P T phase to the broken P T phase. Furthermore, a salient phenomenon of bistable-like P T phase is observed, in which the emitted field possesses a paradox between the two kinds of P T phases. We show that the physical mechanism of this bistable-like phenomenon is a globally inhomogeneous P T phase, in which different spatial regions of the whole structure can possess different P T phases (broken or exact). This study highlights the potential to manipulate the P T phase transition by using optical nonlinearity for many interesting applications.

Non-Hermitian guided modes and exceptional points using loss-free negative-index materials

“…The coalescence of dispersion at a critical value of a c shown in Fig. 2 resembles EPs in PT symmetry very much [12][13][14][15][16][17][18][19][20]. We check the eigenmodes around this point (see Fig.…”

“…The exact phase difference is determined by the sign of ∆/γ. Generally γ is determined by the overlap integral of fields in the gap between the two WGs and its sign is fixed [14,15,28], but sign(∆/γ) can be tuned by changing the resonant conditions of k NIM, PIM in the two WGs, e.g. by changing the index of refraction inside or the thicknesses of WGs.…”

“…The simplest configuration in studying PT symmetric optics is two parallel waveguides (WGs). Such a kind configuration can be readily studied by using Maxwell's equations, and it supports some intriguing optical effects especially the stopped light at exceptional points (EPs) [12][13][14][15] that separate the conserved and broken PT phases [16][17][18][19][20]. However, for an optical wave propagating inside a WG, it contains multiple important physical parameters especially the wavevector k charactering the propagation of phase front and the Poynting vector S presenting the propagation of energy flux.…”

Revisit the Poynting vector in P T-symmetric coupled waveguides

“…In the past decades we have witnessed the rapid advances of non-Hermitian physics, including the parity-time (PT ) symmetry and the exceptional points (EPs) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. By taking into account the active role of loss and gain, non-Hermitian physics applies to open systems without the energy-conservation requirement, and provides a much broader platform for scientists in revealing new physics and exotic applications which have no counterpart in common Hermitian physics.…”

“…By taking into account the active role of loss and gain, non-Hermitian physics applies to open systems without the energy-conservation requirement, and provides a much broader platform for scientists in revealing new physics and exotic applications which have no counterpart in common Hermitian physics. Notable achievements of PTsymmetric optics include the unidirectional invisibility, enhanced sensors, chiral manipulation and various vortex lasers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”