Nanostructured optical waveguide with a highly confined mode

We propose a transmission line working at telecom wavelengths with cross section as small as ${\lambda}^2/39$, which is 1.6 times smaller than that of optimized silicon waveguide. The proposed line can be implemented as a subwavelength fiber with plasmonic cladding. This considerable decrease in the line cross section is achieved by utilizing a plasmonic quasi-antisymmetric mode. The required plasmonic cladding is rather thin, therefore, losses are moderate and could be compensated by using amplifying core materials. Such a transmission line can find applications in densely integrated optical systems.