[Perspective] Plasmonics—turning loss into gain
The light-induced electronic excitations that occur at the surface of metals—plasmons—provide the extraordinary ability to confine electromagnetic energy to the subwavelength scale. Such extreme optical confinement can enhance the light-matter interaction and enable miniaturized optical and optoelectronic devices. However, this confinement requires that plasmonic materials possess free carriers, which unavoidably results in light being lost or absorbed in the system (1). This optical loss has hampered the realization of device designs with ultracompact, on-chip optical components and nanometer-scale resolution imaging. Because of the detrimental effects of plasmonic losses, several avenues are being explored to mitigate the high absorption, such as using gain to compensate for the losses, and synthesizing alternative low-loss plasmonic materials (2). Rather than continuing to pursue low-loss plasmonics approaches, we draw attention to the benefit of losses by high-lighting recent groundbreaking discoveries that were enabled by intrinsic losses in plasmonic systems. Authors: Justus C. Ndukaife, Vladimir M. Shalaev,...