Kagome Flatbands for Coherent Exciton-Polariton Lasing

Abstract

Kagome lattices supporting Dirac cones and flatband dispersions are well-known as a highly frustrated, two-dimensional lattice system. Particularly, the flatbands therein are attracting continuous interest based on their link to topological order, correlations, and frustration. In this work, we realize coupled microcavity implementations of Kagome lattices hosting exciton-polariton quantum fluids of light. We demonstrate precise control over the dispersiveness of the flatband as well as selective condensation of exciton-polaritons into the flatband. Subsequently, we focus on the spatial and temporal coherence properties of the laserlike emission from these polariton condensates that are closely connected to the flatband nature of the system. Notably, we find a drastic increase in coherence time due to the localization of flatband condensates. Our work illustrates the outstanding suitability of the exciton-polariton system for detailed studies of flatband states as a platform for microlaser arrays in compact localized states, including strong interactions, topology, and nonlinearity.

Bloch Oscillations of Hybrid Light-Matter Particles in a Waveguide Array

“…The gradient needed to invoke Bloch oscillations in this waveguide array is oriented in y-direction, perpendicular to the propagation direction. While the use of Gross-Pitaevskii models has been fairly well established for exciton-polaritons in the past, we have successfully expanded these models to take into account sophisticated lattice potentials 32,33 . By tuning the gradient, coupling properties and excitation conditions, different regimes of propagation patterns can be achieved.…”

Observation of Topologically Distinct Corner States in “Bearded” Photonic Kagome Lattices

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] For instance, tremendous research efforts involving Kagome lattices have led to the understanding of a host of intriguing phenomena, ranging from the properties of fractional quantum Hall states, [3] quantum spin liquids, [4,18] charge order, and superconductivity, [9] to compact localized states, [6] anomalous Landau levels, [7,15] and flat-band exciton-polariton emission. [10] As a typical example in photonics, a Corbino-shaped Kagome lattice has been realized [12] for direct observation of flat band non-contractible loop states (NLSs) protected by real-space topology, originally predicted from the "frustrated" hopping models. [2] Recently, the so-called breathing Kagome lattices (BKLs) [19] have been employed as a prototypical platform to study higherorder topological insulators (HOTIs), [20,21] realized in a variety of systems.…”

“…A typical example is the Kagome lattice, [1] which has turned into one of the most studied models in condensed matter physics, ultracold atoms, as well as DOI: 10.1002/adom.202301614 photonics. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] For instance, tremendous research efforts involving Kagome lattices have led to the understanding of a host of intriguing phenomena, ranging from the properties of fractional quantum Hall states, [3] quantum spin liquids, [4,18] charge order, and superconductivity, [9] to compact localized states, [6] anomalous Landau levels, [7,15] and flat-band exciton-polariton emission. [10] As a typical example in photonics, a Corbino-shaped Kagome lattice has been realized [12] for direct observation of flat band non-contractible loop states (NLSs) protected by real-space topology, originally predicted from the "frustrated" hopping models.…”

Enhanced coupling between ballistic exciton-polariton condensates through tailored pumping

“…Ever since the demonstration of Bose-Einstein condensation of exciton-polaritons (from here on polaritons) in planar semiconductor microcavities [1] there has been tremendous effort dedicated to scaling up the number of coupled condensates to form extended systems. The notable candidates for large-scale networks and lattices of polariton condensates are etched micropillar arrays [2,3], metal deposited cavity surface [4], etch-and-overgrowth techniques [5,6], surface acoustic waves [7], and structured nonresonant light source using spatial light modulators [8,9]. On one hand, designing lattices of polariton condensates can offer new insight into the non-Hermitian physics of driven-dissipative quantum fluids obeying Bloch's theorem with strong nonlinearities [10].…”