Causality and phase transitions in PT-symmetrical optical systems

Abstract

We discuss phase transitions in PT-symmetric optical systems. We show that due to frequency dispersion of the dielectric permittivity, an optical system can have PT-symmetry at isolated frequency points only. An assumption of the existence of a PT-symmetric system in a continuous frequency interval violates the causality principle. Therefore, the ideal symmetry-breaking transition cannot be observed by simply varying the frequency.

References in corpus (4)

• PT-symmetry breaking and laser-absorber modes in optical scattering systems
• Visualization of Branch Points in PT-Symmetric Waveguides
• Physical realization of $\mathcal{P}\mathcal{T}$-symmetric potential scattering in a planar slab waveguide
• Exponentially Fragile PT-Symmetry in Lattices with Localized Eigenmodes

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• Unique optical characteristics of a Fabry-Perot resonator with embedded PT-symmetrical grating
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• Theory and Numerical Modelling of Parity-Time Symmetric Structures in Photonics: Boundary Integral Equation for Coupled Microresonator Structures
• Correlated Nonreciprocity around Conjugate Exceptional Points
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• Fundamental issues with light propagation through $\mathcal{P}\mathcal{T}$-symmetric systems
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