Loss compensated extraordinary transmission in hybridized plasmonic nanocavities

Extraordinary optical transmission has been utilized in many optical applications, but the plasmonic losses hinder their full potential. To obtain enhanced transmission, one of the loss compensation methods is to introduce gain. However, an enhanced transmission or even eliminated absorption does not guarantee plasmonic loss compensation. Here, we reveal the distinction between the transmission enhancement mechanisms in gain-assisted plasmonic arrays. To uncover the underlying mechanisms of the modified transmissions, we calculate the effective electric permittivity by employing a self-consistent gain model. We demonstrate that a large transmission enhancement in a plasmonic system composed of periodic nanocavities and coaxially placed nanoislands, is led by the loss compensation, which manifests itself as narrowing in effective permittivity. In contrast, a slight transmission enhancement in a plasmonic array without the nanoislands arises from the background amplification. (paper)