Many of the most exciting applications of metamaterials have so far been hindered by their inherently narrowband response and absorption losses. These issues are fundamentally related to the resonant nature of typical metamaterials, consistent with Kramers-Kronig relations for causal passive media. Active media have therefore been recently proposed to overcome some of these limitations. In particular, parity-time (PT) symmetric systems, which can be implemented with balanced distributions of losses and gain, hold the potential to realize a novel, intrinsically loss-immune platform to control electromagnetic waves, for a variety of applications. For example, we have recently shown that the combination of PT-symmetry with atailored nonlocal response allows realizing loss-immune all-angle negative refraction, and aberration-free planar imaging (figures below) [1,2].
More in general, I am currently exploring many new directions that exploit the unique properties of active, nonlinear, nonlocal and nonreciprocal materials and structures, which hold the promise to revolutionize the field of metamaterials, going drastically beyond the current know-how.
F. Monticone,* C. A. Valagiannopoulos,* and Andrea Alù, “Aberration-Free Imaging Based on Parity-Time Symmetric Nonlocal Metasurfaces,” under review, since September 2015. (manuscript available on arXiv) *Joint first authorship
 C. Valagiannopoulos,*F. Monticone,* and A. Alù, “PT-Symmetric Planar Devices for Field Transformation and Imaging,” Journal of Optics, in press, 2015, (invited paper). *Joint first authorship
 Several works in preparation.