Magnetically Controlled Atomic-Plasmonic Fano Resonances.

Following the efforts of size reduction and the integration of light and vapor systems, great promise is held in the integration of vapor and confined electromagnetic waves. By confining light to nanoscale dimensions, fundamental properties of light-vapor interactions may vary significantly. For example, the state of polarization may be modified as compared with weakly focused beams. Specifically, in transverse magnetic modes, the existence of a longitudinal field component, which is in quadrature to the transverse field, generates a "circular-like" polarized light. Here, by taking advantage of this very property, we study the interaction of confined light and vapor in a coupled system of plasmons and atomic vapors in the presence of magnetic fields. Our results show that the spectroscopic nature and Fano resonances of the hybrid plasmonic-atomic system are greatly altered. In parallel, we also exploit the existence of the atoms in proximity to the plasmonic mode to probe the polarization state of the electromagnetic field and reveal the longitudinal-to-transverse ratio between the plasmonic modes components in the near field. Interestingly, our system maps the amplitude and phase information of the electromagnetic modes to the spectral domain. As such, combining magnetic fields with the coupled plasmonic-atomic system has the potential for future applications in high spatial resolution magnetometry, near-field vectorial imaging, and magnetically induced switching and tuning.