A GaAs-based plasmonic source employing a nanoscale vertical cavity

In this paper, a new structure of a vertical cavity plasmonic source is presented. The structure, which is adopted from a metal-semiconductor-metal plasmonic photodetector, contains a gold substrate, n-type GaAs layer, active GaAs layer and p-type GaAs layer, respectively from bottom to up. A subwavelength aperture and metal gratings on both sides of the aperture are placed on the top of the device and act both as a gold clad and as the contact for applying DC bias. The metal gratings are improved by adding SiO2 between metal grooves and semiconductor. Applying voltage bias to p-and n-regions leads to photons generation in the active region. The generated photons in the active region excite a resonant surface plasmonic mode in the nanoscale cavity just below the aperture. One can use light outflowing from the nanoscale aperture, with wavelength of 882nm, as a source to excite an arbitrary plasmonic guiding structure. The output beam has a suitable concentration so that in a 1000nm distance from the aperture, still 37% of the power is concentrated in a width of 50nm which is almost a unique specification among plasmonic sources, so far. The function of the device is validated using finite-difference time-domain numerical algorithm.