Metallic or Dielectric Metasurfaces? Which one is better?

Abstract

Metasurfaces are an array of periodic subwavelength nanostructures that resonantly couple to the incident light. Such nanostructured surfaces can reproduce the functions of bulk optics, and on occasions, offer new functionalities that are not possible with conventional diffractive optics. Metallic metasurfaces, employing resonant oscillation of surface-plasmons, can confine light in the nanoscale gaps, so-called hot spots, with extreme sensitivity to the refractive index of the environment. However, the price of such characteristics is the high ohmic losses of metallic nanoparticles. On the other hand, high-index dielectric and semiconductor metasurfaces are lossless. They can stimulate Mie resonances in a multipolar fashion, applicable to both linear and nonlinear regimes, although they produce much weaker hot spots. The benefits of metallic or dielectric metasurfaces have been a subject of debate in the last decade. In this seminar, I review my journey in employing metallic to dielectric and semiconductor metasurfaces in both linear and nonlinear regimes. I will discuss the benefits of each of them for certain applications ranging from ultra-sensitive detection to near-infrared imaging.