Feasibility of GaAs-based metal strip surface plasmon nano-lasers

The authors present a theoretical analysis of metallic strip surface plasmon nano-lasers that are compatible with III??V semiconductor materials and fabrication technologies. The design mimics a ridge waveguide laser, where the ridge is a metallic strip that sits on top of a semiconductor slab waveguide. We discuss the formation and characteristics of a mode that is bound to the metallic strip and evaluate the possibility of compensating its propagation loss with the gain from the semiconductor slab. We find that the bound mode is a hybrid of the modes of the metallic strip and those of the semiconductor slab and that by varying the internal coupling, it is possible to engineer extremely strong lateral mode confinement while also mitigating the high propagation losses that are typically associated with surface plasmon modes. Using a realistic gain model for GaAs and a new analysis of the confinement factor, we find that carrier concentrations in the region of 3 x 10¹⁸ cm^??3 can compensate for the bound mode??s propagation losses, in the region of 1000 cm^??1, at room temperature. This design has many desirable features including single lateral mode operation, a high confinement-to-loss figure of merit and the potential for relatively straightforward in-situ fabrication.