Gain-assisted indented plasmonic waveguide for low-threshold nanolaser applications

A subwavelength plasmonic indented waveguide with an active InGaAsP core is proposed. The characteristics of the gap plasmon mode and gain required for lossless propagation are investigated and analyzed by the finite element method. We numerically calculate the normalized mode areas and percentages of energy confined in InGaAsP and metal for plasmonic nanolaser applications. It is shown that the indentation of the sidewalls has an optimal value for which the lasing threshold gain is minimal. The structure could enable low-threshold subwavelength lasing and applications for optoelectronic integrated circuits.