Engineering a light–matter strong coupling regime in perovskite-based plasmonic metasurface: quasi-bound state in the continuum and exceptional points

Abstract

We present theoretically the formation of exciton-photon polaritons and excitonsurface plasmon polaritons in perovskite-based subwavelength lattice on metallic plane. It is showed that the later polaritons will be achieved as the perovskite layer is ultra thin (<50nm) while the co-existence of both polaritons will dominate as the thickness of the perovskite metasurface approaches wavelength-scale. In the two cases, the lower polaritonic branches consist of dark and bright modes corresponding to infinite and finite radiative quality factor, respectively. Another salient property in this work is that it allows one to obtain exceptional points (EPs) in momentum space with a four-fold enhancement of local density of states through engineering the perovskite metasurface. Our findings show that perovskite metasurface is an attractive and rich platform to make polaritonic devices, even with the presence of lossy metallic layer.

Polariton Bose-Einstein condensate from a Bound State in the Continuum

“…Strong radiation-matter coupling between a QW excitonic transition and such photonic modes leads to BIC polaritons. [28][29][30] The actual sample used in this work is a waveguide comprising 12 (nominally, 20 nm thick) GaAs quantum wells separated by (20 nm thick) Al 0.4 Ga 0.6 As barriers, and sitting on top of a 500 nm thick Al 0.8 Ga 0.2 As cladding (see Fig. 1).…”

Realization of Polaritonic Topological Charge at Room Temperature Using Polariton Bound States in the Continuum from Perovskite Metasurface

“…However, due to their hybrid exciton-photon nature, the quality factor of pol-BICs is balanced between the nonradiative losses of the excitonic component and the one from the photonic BIC. [43] They are thus quasi-BICs, whose quality factor is limited by non-radiative losses. Moreover, the C 4 symmetry of the square-lattice imposes that the quality factor of photonic BICs decreases as 2 k x at oblique angles.…”

“…While most of the milestones of polaritonic physics have been achieved with excitonic materials operating at cryogenic temperatures (≈10 K), recent progress in materials science has promoted many polaritonic demonstrations at room temperature with a wide variety of high bandgap semiconductors, ranging from GaN, [24,25] ZnO, [26] to organic semiconductors, [27,28] and transition metal dichalcogenide monolayers, [29,30] as well as perovskite materials. [31][32][33][34][35][36][37][38][39][40][41] Very recently, the strong coupling regime between photonic BICs and excitonic resonances has been theoretically suggested, [42][43][44][45] with two experimental demonstrations. [46,47] The result of such a coupling is the formation of polariton-BICs (pol-BICs): hybrid excitations that are completely decoupled from the radiative continuum.…”

“…[38] Most recently, it has been theoretically suggested that perovskite metasurfaces can be harnessed to engineer the imaginary part (i.e., losses) of the polaritonic energy-momentum dispersion at room temperature via BIC and exceptional point concepts. [43,45] On the other hand, purely photonic BICs in perovskite-based resonant metasurface have been reported to make ultra-fast switches [7] and tunable microlasers. [49] In this work, we experimentally demonstrate the formation of pol-BICs in an excitonic metasurface made from hybrid 2D perovskites.…”

Coexistence of Surface Lattice Resonances and Bound states In the Continuum in a Plasmonic Lattice

“…We investigated the role of the superstrate for the nanodisk array with a period p = 425 nm in sustaining both LSPRs and SLRs. n sup is varied from 1.0 (air) to 2.4 (TiO 2 [32] or perovskite film [33,34]). This cor- responds to a variation in the index contrast, defined by ∆n = n sup − n sub , from -0.46 to 0.94.…”