PT-symmetric in optics, Zyablovsky A.A., Vinogradov A.P., Pukhov A.A., Dorofeenko A.V., Lisyansky A.A.

We demonstrate the existence of a spectrally narrow localized surface state, the so-called optical Tamm state, at the interface between one-dimensional magnetophotonic and nonmagnetic photonic crystals. The state is spectrally located inside the photonic band gaps of each of the photonic crystals comprising this magnetophotonic structure. This state is associated with a sharp transmission peak through the sample and is responsible for the substantial enhancement of the Faraday rotation for the corresponding wavelength. The experimental results are in excellent agreement with the theoretical predictions.

We study the optical properties of a photonic crystal interfaced with a uniform medium with the negative dielectric constant or with another photonic crystal. We show that, at such an interface, nonpropagating surface states may arise. These states result in a sharp feature in the transmission and reflection spectra of the system. We also show that interfacing magnetic and nonmagnetic photonic crystals gives rise to giant Faraday and Kerr effects.

We discuss phase transitions in $\mathcal{PT}$-symmetric optical systems. We show that, due to frequency dispersion of the dielectric permittivity, an optical system can have $\mathcal{PT}$ symmetry at isolated frequency points only. An assumption of the existence of a $\mathcal{PT}$-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.

We consider exciting surface plasmon polaritons in the Kretschmann configuration. Contrary to common belief, we show that a plane-wave incident at an angle greater than the angle of total internal reflection does not excite surface plasmon polaritons. These excitations do arise, however, if the incident light forms a narrow beam composed of an infinite number of plane waves. The surface plasmon polariton is formed at the geometrical edge of the beam as a result of interference of reflected plane waves.