Light mediated resonant coupling between nano-scale particles and discrete level quantum media is a flourishing field of research [1]. Such coupling constitutes a hybridized material, exhibiting phenomena such as Fano linshapes, strong coupling, Purcell enhancements and long range Van der Waals interactions. Specifically, the combination of a nano-particles and atomic vapor results in a novel and fascinating test bed for fundamental aspects in light-vapor interactions.
Recently we have demonstrated the interaction of surface plasmon polaritons with Rb vapor [2]. Here, we present resonant interactions between the localized surface plasmon (LSP) modes implemented by an array of ellipsoidal gold nano-particles embedded in Rb atomic vapor. A cross section illustration of an individual nano-antenna is presented in Fig. 1a. A SEM of an individual particle as well as the array is presented in Fig. 1b. Such nano-particle array experiences a LSP resonant mode at ~620nm and ~800nm with the polarization of light aligned along the short and long axis of ellipse respectively. We excite the array at the wavelength of 780nm resonant with the D2 line of Rb, and record the reflection spectrum (Fig 1c for short axis excitation, and Fig 1d for long axis). As we vary the incident power, the 85Rb dominant transition is saturated, with different saturation thresholds, for both polarizations directions as a consequence of the different electric field density associated with these polarizations (see insets 1c and 1d). The presented hybridized LSP-Rb material is expected to provide optical functionalities previously inaccessible in each individual material, as well as serving as a test bed for exploring the nature of atomic interactions in the vicinity of metal surfaces.
Figure 1: (a) Illustration of the plasmonic-atomic device layers (b) SEM of the nano particle array (c) Power depended reflection spectra of the hybrid platform for (c) short axis polarization and (d) long axis excitation.
[1] Schuller, J. A. et al. Plasmonics for extreme light concentration and manipulation. Nat. Mater. 9, 193–204 (2010).
[2] L. Stern, M. Grajower, and U. Levy, Fano resonances and all-optical switching in a resonantly coupled plasmonicatomic system, Nature Commun 5, (2014).
liron.stern@mail.huji.ac.il