Highly directive and Gaussian far-field emission from "giant" photonic trumpets

Photonic trumpets are broadband dielectric antennas that efficiently funnel the emission of a point-like quantum emitter-such as a semiconductor quantum dot-into a Gaussian free-space beam. After describing guidelines for the taper design, we present a "giant" photonic trumpet. The device features a bottom diameter of 210 nm and a 5 mu m wide top facet. Using Fourier microscopy, we show that 95% of the emitted beam is intercepted by a modest numerical aperture of 0.35. Furthermore, far-field measurements reveal a highly Gaussian angular profile, in agreement with the predicted overlap to a Gaussian beam M-g = 0.98. Future application prospects include the direct coupling of these devices to a cleaved single-mode optical fiber. The calculated transmission from the taper base to the fiber already reaches 0.59, and we discuss strategies to further improve this figure of merit. (C) 2015 AIP Publishing LLC.