Directional Modulation of Fluorescence by Nanowire‐Based Optical Traveling Wave Antennas

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Plasmonic optical antennas can direct light from quantum emitters and improve nanophotonics device efficiency. In this study, composite structures with V‐shaped Ag nanowires (V‐Ag NWs) and quantum dots (QDs) are designed and fabricated. V‐Ag NWs serving as optical traveling wave antennas (TWAs) are employed for QD fluorescence emission direction control. The modulated emission directionality is achieved up to 11.8 dB, and the azimuthal angle half‐power bandwidth is as narrow as 35°. The azimuthal radiation is effectively tuned from 0° to over 40° by changing the bending angles of the structures. Finite‐difference time‐domain and Green's function methods are used to analyze the far field radiation patterns that are in good agreement with the experiment measurements. TWAs are easy to fabricate and integrate with optical waveguide. Thus, they are excellent tools for realizing unidirectional fluorescence emission and are potentially applicable in integrated plasmonics and nanophotonics devices.