Electrically pumped dielectric loaded surface plasmon waveguide laser

Abstract

Here we experimentally demonstrate an electrically pumped surface plasmon waveguide laser, which generates surface plasmons on a flat metal surface. The laser is formed by a narrow strip of electrically pumped semiconductor optical gain medium placed close to a flat silver surface. The gain medium is electrically pumped via long thin laterally connected semiconductor pathways. The semiconductor gain medium acts as a dielectric load to localize the surface plasmon component on the silver surface. Lasing is demonstrated at wavelengths near 1500 nm with a section of waveguide which forms a Fabry-Perot cavity. The lasing mode is shown to be the predicted zero order transverse magnetic mode, which allows the greatest miniaturization of the laser size. Lasing is demonstrated at low temperatures due to fabrication imperfections. However, analysis of the results shows the structure has good potential for room temperature operation. With the fabricated device parameters a material gain of 55 cm⁻¹ is required in theory to overcome metal losses, and the confinement factor for the laser waveguide is 0.5. This laser demonstration shows that lateral electrical pumping schemes can be realized. Furthermore, that the schemes provide sufficient pumping of the gain medium to overcome metal losses in surface plasmon waveguides.