Injection of Orbital Angular Momentum and Storage of Quantized Vortices in Polariton Superfluids

Abstract

We report the experimental investigation and theoretical modeling of a rotating polariton superfluid relying on an innovative method for the injection of angular momentum. This novel, multipump injection method uses four coherent lasers arranged in a square, resonantly creating four polariton populations propagating inwards. The control available over the direction of propagation of the superflows allows injecting a controllable non-quantized amount of optical angular momentum. When the density at the center is low enough to neglect polariton-polariton interactions, optical singularities, associated to an interference pattern, are visible in the phase. In the superfluid regime resulting from the strong nonlinear polariton-polariton interaction, the interference pattern disappears and only vortices with the same sign are persisting in the system. Remarkably the number of vortices inside the superfluid region can be controlled by controlling the angular momentum injected by the pumps.Introduction. In planar semiconductor microcavities, the strong coupling between light (photons) and matter (excitons) [1] gives rise to exciton-polaritons, with specific properties such as a low effective mass, inherited from their photonic component, and strong nonlinear interactions due to their excitonic part. These quasi-particles offer a great opportunity to revisit in solid state materials the interaction between light and matter, first explored in atomic physics. Polaritonic systems are easily controllable by optical techniques and, due to their finite lifetimes, are ideal systems for studying out-of-equilibrium phenomena [2,3]. In analogy with the atomic case [4,5], the superfluid behavior of polariton quantum fluids has been theoretically predicted [6] and experimentally confirmed [7][8][9].Quantized vortices are topological excitations characterized by the vanishing of the field density at a given point (the vortex core) and the quantized winding of the field phase from 0 to 2π around it. Together with solitons, they have been extensively studied and observed in nonlinear optical systems [10] [17][18][19][20][21] in polariton fluids, more detailed studies of vortices and vortex arrays are still needed in order to achieve a better understanding of polariton superfluidity and of vortex dynamics, as well as to achieve the implementation of quantum technologies [22][23][24].Polariton systems have been shown to reveal a large variety of effects with the formation of stable vortices [20,25] and half vortices [26,27] as well as the formation of single vortex-antivortex (V-AV) pairs [17,18,28], and spin-vortices [29]. The formation of lattices of vortices and of V-AV pairs has been theoretically predicted for cavity-polaritons [30][31][32] and observed in the case of patterns induced by metallic depo-

Spin Textures of Exciton-Polaritons in a Tunable Microcavity with Large TE-TM Splitting

“…Much effort has been devoted to the development of methods to create OAM in a controllable way in a polariton system, such as optical imprinting [13,14] and chiral polaritonic lenses [15]. Meanwhile, quantized phase [16][17][18] and spin vortices [10] may also form spontaneously in exciton-polariton superfluids and nonequilibrium polariton Bose-Einstein condensates (BECs) subject to disorder potential [10,16], although the exact origin of the latter remains unclear.…”

Vortex-stream generation and enhanced propagation in a polariton superfluid

“…In the last decade, many efforts have been made to control and manipulate the generation and propagation of vortices in polariton systems [7][8][9][10]. The vortices in a superfluid are collective excitations formed by a low density core with quantized circulation around it, which makes them resilient to spontaneous decay (i.e.…”

Optically Controlled Orbital Angular Momentum Generation in a Polaritonic Quantum Fluid

“…Polaritons form a quantum fluid, and prominent examples of observed phenomena include parametric amplification [18] and Bose condensation ( [19,20] and references therein). Polaritonic quantum fluids can support vortices [21,22], and it was recently demonstrated that OAM can be transferred to polaritonic Bose-Einstein condensates using chiral polaritonic lenses [23], and that the number of vortices can be controlled by controlling the OAM of the pump beams [24,25].…”

“…Polaritons form a quantum fluid, and prominent examples of observed phenomena include parametric amplification [18] and Bose condensation ([19,20] and references therein). Polaritonic quantum fluids can support vortices [21,22], and it was recently demonstrated that OAM can be transferred to polaritonic Bose-Einstein condensates using chiral polaritonic lenses [23], and that the number of vortices can be controlled by controlling the OAM of the pump beams [24,25].The question remains whether the relatively strong interaction between polaritons can be used to manipulate, in a well-controlled fashion, the orbital and/or spin angular momentum of polaritons (and thus the light field emitted from the cavity). For example, is it possible to use a beam with OAM of m p and create additional OAM contributions, say two components of OAM m 1 and m 2 , and to use the light beam characteristics of frequency and intensity to control m 1 and m 2 ?…”