Using metamaterial to tune the atom-surface interaction

We are exploring the strong scientific potential of merging atoms with nano-structured material, where the electromagnetic environment can be engineered almost at will, for new atom-light coupling perspectives. We focused on metallic metasurfaces with a periodic arrangement of nano-slits (see Figure). With these, we could tune the surface plasmonic resonance such that it coincides with an atomic resonance. We show that the atomic resonance was deeply modified by the presence of the broad surface plasmonic resonance, leading to a Fano-type lineshape [1]. However, we need to consider the Casimir-Polder interaction to address weak atomic transition shifts, not captured with our Fano model. Interestingly, besides the usual non-resonant contribution, the Casimir-Polder interaction was also due to the plasmonic resonance itself, which we were able to vary the frequency by changing the geometry of the metasurface. With this technology in hand, we realize the first tuneable Casimir-Polder device in the optical domain and measure the Casimir-Polder absorptive response [2]. We proposed a compact version of this device, where the metasurfaces were engraved on the tip of optical fibers for future gas-sensing devices [3]. We also investigated the enhancement of weak atomic signals thanks to the metamaterial, and we were the first group to realize the coupling of an electric quadrupole transition with a surface plasmonic resonance [4]. Finally, we proposed a metasurface design to shape the vacuum environment such as it becomes anisotropic, in planes normal to the surface. This configuration gives extra correlations (otherwise absent in the usual isotropic vacuum) in the atomic induced-dipole moment leading to long lifetime coherences in the ground state manifold of the atom [5].

The atom/metamaterial hybrid system. 10 metamaterials of size 200 μm × 200 μm with different plasmon resonance are engraved on a windows (see real image picture on the right upper corner). The metamaterial is a periodic arrangement (period ~400 nm) of nano-slits (see SEM image on the right).

[1] S. A. Aljunid, E. A. Chan, G. Adamo, M. Ducloy, D. Wilkowski, and N. I. Zheludev, “Atomic Response in the Near-Field of Nanostructured Plasmonic Metamaterial,” Nano Lett., vol. 16, no. 5, pp. 3137–3141, May 2016, doi: 10.1021/acs.nanolett.6b00446.

[2] E. A. Chan, S. A. Aljunid, G. Adamo, A. Laliotis, M. Ducloy, and D. Wilkowski, “Tailoring optical metamaterials to tune the atom-surface Casimir-Polder interaction,” Sci. Adv., vol. 4, no. 2, Art. no. 2, Feb. 2018, doi: 10.1126/sciadv.aao4223.

[3] E. A. Chan, G. Adamo, S. A. Aljunid, M. Ducloy, N. Zheludev, and D. Wilkowski, “Plasmono-atomic interactions on a fiber tip,” Appl. Phys. Lett., vol. 116, no. 18, p. 183101, May 2020, doi: 10.1063/1.5142411.

[4] E. A. Chan, S. A. Aljunid, G. Adamo, N. I. Zheludev, M. Ducloy, and D. Wilkowski, “Coupling of atomic quadrupole transitions with resonant surface plasmons,” Phys. Rev. A, vol. 99, no. 6, p. 063801, Jun. 2019, doi: 10.1103/PhysRevA.99.063801.

[5] E. Lassalle et al., “Long-lifetime coherence in a quantum emitter induced by a metasurface,” Phys. Rev. A, vol. 101, no. 1, p. 013837, Jan. 2020, doi: 10.1103/PhysRevA.101.013837.