Optical seminar | 19 November 2021

Moscow Institute of Physics and Technology
A story about meta-atoms, chirality, and unusual vacuum

Strong coupling is a distinct regime of light−matter interaction, when the Rabi frequency exceeds the dissipation rates of the system. This regime of interaction manifests itself in coherent oscillations of energy between the matter and photonic subsystems. Typically, this regime is attained by coupling quantum emitters to optical cavities. However, very limited oscillator strength of quantum emitters leads only to moderate coupling strengths.
In this talk I will present an alternative platform for engineering of polaritonic states. To that end, we leverage plasmonic resonances of metallic “molecules” having much larger oscillator strength, and study potential effects of coupling these meta-atoms to optical cavities. I will show that we can reach ultrastrong coupling between plasmonic meta-atoms and cavity photons by packing a single layer of plasmonic nanorods inside a Fabry-Perot microcavity. This simple platform allows us to reach the ultrastrong coupling regime at room temperature, atmospheric pressure, and without the use of magnetic fields. Furthermore, we can leverage the concept of plasmonic meta-atoms in order to boost the vibrational light−matter coupling strength in organic platforms, which may have impoprtant implications on our ability to modify the kitetics of chemical reactions.
Next, we make our plasmonic meta-atoms chiral and study the effect of coupling these meta-atoms to cavity modes. At the same time, we reveal fundamental limitations on the enhancement of dichroic effects in planar resonators. To overcome this difficulty, I will present the model of a single-handedness chiral optical cavity supporting only an eigenmode of a given handedness without the presence of modes of other helicity. This structure expands the set of tools for investigations of chiral matter and opening the door towards studies of chiral electromagnetic vacuum states.
To conclude the talk, I will show how exotic vacuum (Casimir) forces between metallic micro-mirrors in a solution enable self-assembly of Fabry-Perot cavities with fundamental resonances in teh visible range. Furthermore, by placing an excitonic material in the self-assembled cavity, we are able to realize polaritonic states, whose properties can be controlled in real time.

Denis G. Baranov et al, "Ultrastrong coupling between nanoparticle plasmons and cavity photons at ambient conditions", Nat. Commun. 11, 2715 (2020)
Manuel Hertzog et al, "Enhancing vibrational light-matter coupling strength beyond the molecular concentration limit using plasmonic arrays", Nano Lett. 21, 1320 (2021)
Battulga Munkhbat et al, "Casimir microcavities for tunable self-assembled polaritons", Nature 597, 214 (2021)
Kirill Voronin, Alexey Taradin, and Denis G. Baranov, "Single-handedness chiral optical cavities", arXiv:2104.14230