Active Control of Trapped Modes in Metasurfaces with a Gain-Loss Superstrate

One of the main challenges in modern optics and photonics is the development of metastructures that allow active control of the response to an incident light wave. This work proposes a novel method for excitation of high- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${Q}$</tex> resonances related to trapped modes arising due to periodic gain-loss asymmetry of the superstrate in a dielectric metasurface. By controlling the external pump parameter, one can control the resonant properties of trapped modes without disturbing the geometry of the system. The performance of the proposed periodic gain-loss metasurface depend on the polarization of the normally incident wave, and makes it attractive for nanophotonics applications.