Efficient Single Photon Emission and Collection Based on Excitation of Gap Surface Plasmons

Combining the advantages of ultrahigh photon emission rates achievable in the gap surface plasmon polaritons with high extraction decay rates into low-loss nanofibers, we demonstrate theoretically the efficient photon emission of a single dipole emitter and one-dimensional nanoscale guiding in metallic nanorod-coupled nanofilm structures coupled to dielectric nanofibers. We find that total decay rates and surface plasmon polariton channel decay rates orders of magnitude larger than those characteristic of metallic nanofilms alone can be achieved in ultrastrong hot spots of gap plasmons. For the requirement of practical applications, propagating single photons with decay rates of $290{\gamma }_0–770{\gamma }_0$ are guided into the phase-matched low-loss nanofibers. The proposed mechanism promises to have an important impact on metal-based optical cavities, on-chip bright single photon sources and plasmon-based nanolasers.

Figure 1

Schematic diagram of Ag nanorod-coupled Au nanofilm gap plasmon system with a designed nanofiber.

Figure 2

Total normalized decay rates ${\gamma }_{\text{total}}/{\gamma }_0$ and SPP channel normalized decay rates ${\gamma }_{\mathrm{SPP}}/{\gamma }_0$ for a dipole emitter (a) at the middle of the gap and (b) at the left corner of the gap, as a function of the length $a$ of the nanorod. The gap between nanorod and nanofilm is 10 nm and $\lambda =680\mathrm{nm}$. The insets in Figs. 2 and 2 are electric field patterns (on the tangent $xz$ plane with the nanorod) of quadrupolar and dipolar gap plasmons.

Figure 3

${\gamma }_{\mathrm{SPP}}/{\gamma }_0$ and ${\gamma }_{\text{fiber}}/{\gamma }_0$ for the dipole emitter (a) at the middle of the gap and (d) at the left corner of the gap with a varying of the length $a$ of the Ag nanorod. Electric field patterns of the $z=282\mathrm{nm}$ plane (in water 30 nm above the nanofilm) for $a=135\mathrm{nm}$ (b) without and (c) with the nanofiber for a quadrupolar gap mode with a size of $6\times 3\mu {\mathrm{m}}^2$, and electric field patterns of the $z=282\mathrm{nm}$ plane for $a=45\mathrm{nm}$ (e) without and (f) with the nanofiber for the dipolar gap mode.

Figure 4

Changes of ${\gamma }_{\text{fiber}}/{\gamma }_0$ when varying the distances (a) $d$ and (b) $d_1$. In (a), the emitter is fixed at $d_1=d/2$ under the nanorod. The maximum ${\gamma }_{\text{fiber}}/{\gamma }_0$ appears when the emitter is nearest the nanorod because of the existence of hot spots.