Fabrication of Metal Embedded Nano-Cones for Single Quantum Dot Emission

High efficiency in the extraction, transmission and detection of single and entangled photons is one of the most significant factors to provide general usage and to suppress the bit-error rate in optical communication networks. We propose and realize metal embedded nanostructures with quantum dots (QDs) as photon sources to meet these challenges on the emitter side. Advantages of the process are the ability of fast nanometer-scale fabrication and the high reproducibility and yield. Mesas with typical taper angles of 20--30° and diameters between 100 nm and 1 μm were produced; these nanostructures are referred to as "cones" in this work. The dependence of the taper angle on the composition of the etched cone material is discussed, focusing on the contribution of indium. The nano-cones used as photon sources were embedded in highly reflective metal and turned upside down to provide efficient and partly directed photon extraction. We present the selection of 1.35 μm photons emitted from a single QD as a result of embedding only a small number of dots in a nanometer sized cone.