Controlled low-level covalent functionalization of single-wall carbon nanotubes (SWCNTs) has refocused the attention of the nanophotonics community on the use of SWCNTs as promising building blocks in photonic circuits due to their recently discovered property of room temperature single photon emission.¹ Further, these new emitting states introduced through chemically stable oxygen² and aryl diazonium dopants³ exhibit a significant increase in photoluminescence (PL) quantum yield and sensitivity to their dielectric environment, which enables their use in imaging and sensor applications.⁴ However, successful integration into waveguide structures and other photonic circuits requires a comprehensive understanding of the angular emission behavior of these dopant sites. One powerful microscopy technique to study the angular emission properties of emitters is Back focal plane (BFP) imaging, which enables to distinguish different radiation channels⁵, to reveal emitter orientations⁶ and magnetic light properties⁷, amongst others.

We present a refinement of the covalent doping procedure^2,3 to achieve the control of the doping level and type of dopant down to the introduction of individual dopant sites in a short timescale. At the same time this procedure is compatible with protocols for isolating chirality sorted and rather long SWCNTs⁸, which enables us to study the length dependence of the angular emission as a function of SWCNT length. In contrast, we also investigate the spatially localized emission from individual dopant sites along the SWCNTs to learn in which angles the emission occurs and to be able to design waveguides tailored specifically to the emission properties. Further we show the significant redirection of emission when placing doped SWCNTs on plasmonic gold thin films. Both, the pristine E₁₁ and the dopant E₁₁^*emission can launch different propagating surface plasmons along the metal interface. These plasmons can be coupled into propagating light via leakage radiation and observed in the BFP.

¹ X. Ma, et. al., Nat. Nanotechnol. 2015, 10, 671. ² S. Ghosh, et al., Science, 2010, 330, 1656. ³ Y. Piao, et al., Nat. Chem., 2013, 5, 840. ⁴ H. Kwon, et. al., J. Phys. Chem. C 2015, 119, 3733. ⁵ N. F. Hartmann, et. al., ACS Nano 2013, 7, 10257. ⁶ A. Lieb, et. al., J. Opt. Soc. Am. B 2004, 21, 1210. ⁷ T. H. Taminiau et. al., Nat. Commun. 2012, 3, 979. ⁸ N. F. Hartmann, et. al., Nanoscale 2015, 7, 20521.