Controlling wave fronts with tunable disordered non-Hermitian multilayers.

Unique and flexible properties of non-Hermitian photonic systems attract ever-increasing attention via delivering a whole bunch of novel optical effects and allowing for efficient tuning light-matter interactions on nano- and microscales. Together with an increasing demand for the fast and spatially compact methods of light governing, this peculiar approach paves a broad avenue to novel optical applications. Here, unifying the approaches of disordered metamaterials and non-Hermitian photonics, we propose a conceptually new and simple architecture driven by disordered loss-gain multilayers and, therefore, providing a powerful tool to control both the passage time and the wave-front shape of incident light with different switching times. For the first time we show the possibility to switch on and off kink formation by changing the level of disorder in the case of adiabatically raising wave fronts. At the same time, we deliver flexible tuning of the output intensity by using the nonlinear effect of loss and gain saturation. Since the disorder strength in our system can be conveniently controlled with the power of the external pump, our approach can be considered as a basis for different active photonic devices.

Asymmetric resonance in selective reflection: explanation via Fano-like mechanism.

Fano mechanism is the universal explanation of asymmetric resonance appearing in different systems. We report the evidence of Fano-like resonance in selective reflection from a resonant two-level medium. We draw an analogy with the asymmetric resonance previously obtained for the coupled oscillators. We also take into account the effects of dielectric background and local-field correction and connect our results with optical bistability.

Nonparaxial Airy beams: role of evanescent waves.

We report on the propagation dynamics of Airy light beams under nonparaxial conditions. The partial waves forming the Airy beam can be divided into two parts, the first of which contains only propagating waves, while the second part consists of evanescent waves. In this Letter we propose the concept of the evanescent Airy beam. We analyze the structure of the ideal evanescent Airy beam, the initial profile of which has the Airy form, while its spectral decomposition consists of only evanescent partial waves. Also, we discuss the refraction of the Airy beam through an interface and investigate the field of the transmitted Airy beam.

Negative propagation of vector Bessel beams.

Energy characteristics of the superposition of TE- and TM-polarized electromagnetic Bessel beams are studied. For some phase differences between TE and TM waves the components of the Poynting vector vary in sign. We call this situation "negative propagation," because locally the beam may behave like a wave propagating in the direction opposite to the conventional one. We predict the following phenomena, which should confirm negative beam propagation: reflection of the beam from a circular aperture and unusual movement of microparticles in the beam.