Cloaking a large nanostructure by a single quantum emitter

21.06.2013, 00:00

Newsletter 6

The past decade has witnessed a growing fascination with the effect that metallic structures have on the optical properties of atoms and molecules. In the cases studied, the metallic structure usually acts as an optical antenna either to modify the spontaneous emission, to open new non-radiative channels or to enhance the Raman cross-section. We have now asked the question how a single quantum emitter could affect the optics of a metallic structure. In particular, we have examined two extreme regimes: very small particles whose optical properties are dominated by absorption, and "large" nanoparticles dominated by scattering. To treat the coherent interaction of incident light with a composite of a metallic particle and a quantum emitter (part (a) of figure), we have developed a general theoretical platform based on quantized radiation in absorptive and inhomogeneous media and have examined the response of the composite as a function of the structure size and separation from the emitter. In the case of larger structures, we show that a single atom or molecule can eliminate both scattering and absorption so that the metallic structure is cloaked. This is particularly impressive because the metallic structure alone would nearly fully block the incident light! Part (b) of the figure illustrates an example where an incident beam of light goes through the emitter-metallic composite without any distortion. For comparison we show the free-space propagation of the same beam in part (c) of the figure. Since the emitter transition can be manipulated in various ways (Stark effect, photo-switching, optical pumping, etc.), the composite system or a macroscopic array of such structures could act as an active metamaterial, allowing active switching of the beam.

Group: Sandoghdar Division
Reference: X. Chen et al., Phys. Rev. Lett. 110, 153605 (2013).