Low threshold nanorod-based plasmonic nanolasers with optimized cavity length

In this article two optically pumped nanorod-based plasmonic nanolasers which composed of two coupled metal-insulator-semiconductor (MIS) hybrid plasmonic waveguides are investigated. In the first structure, a common metallic nanorod is utilized to construct a semiconductor-insulator-metal-insulator-semiconductor (SIMIS) nanostructure while in the second one, the semiconductor part is shared and a metal-insulator-semiconductor-insulator-metal (MISIM) based plasmonic nanolaser is formed. Simulation results based on the finite element method (FEM) show that the SIMIS structure with nanorods' radii of 40 nm and insulator layer thickness of more than 12.67 nm has lower threshold and simultaneously lower normalized mode area at the lasing wavelength of 490 nm compared to the previously reported MIS nanostructure with the same parameters. The simulation results for the second proposed structure show that the MISIM based spaser has a lower effective mode index and consequently lower wave number at the wavelength of 490 nm, compared to both SIMIS and MIS based nanocavities. This results in less challenge for coupling to on-chip waveguides. The cavity length of the presented nanorod-based spasers has been optimized by considering the lasing mode propagation distance as the nanocavity length which leads to a better light matter interaction enhancement.