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

Abstract

We report an extended family of spin textures of zero-dimensional exciton-polaritons spatially confined in tunable open microcavity structures. The transverse-electric-transverse-magnetic (TE-TM) splitting, which is enhanced in the open cavity structures, leads to polariton eigenstates carrying quantized spin vortices. Depending on the strength and anisotropy of the cavity confining potential and of the TE-TM induced splitting, which can be tuned via the excitonic or photonic fractions, the exciton-polariton emissions exhibit either spin-vortex-like patterns or linear polarization, in good agreement with theoretical modeling. DOI: 10.1103/PhysRevLett.115.246401 PACS numbers: 71.36.+c, 42.55.Sa, 71.70.Ej, 78.55.Cr Vortices are topological entities associated with quantized orbital angular momentum (OAM) which occur in many physical systems in optics, condensed matter, cosmology, and fundamental particles, characterized by a phase winding of an integer multiple of 2π around a core. Structured light carrying OAM can be used in a broad range of applications including quantum information [1-3], topological photonics [4], optical forces [5], and vacuum slow light [6]. The coherent superposition of two modes with antirotating OAM and opposite photon pseudospin (circular polarization) is shown to lead to new types of topological entities, usually referred to as vector vortex beams in photonics [7][8][9] and spin vortices in excitonpolaritons [10,11], characterized by quantized polarization winding instead of pure phase winding. Vector vortex lattices were reported in semiconductor lasers [12].On the other hand, strong exciton-photon coupling in semiconductor microcavities leads to formation of polaritons. 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.Another notable characteristic of semiconductor microcavities is the transverse-electric-transverse-magnetic (TE-TM) splitting [19], which defines two nondegenerate polarization directions relative to the in-plane wave vector [20]. In optical microcavities, TE-TM splitting enables the observation of interesting optical phenomena including the optical spin-Hall effect [21], magneticmonopole-like half solitons [22], spinor condensate with half-quantum circulation [23], and possibly topological insulators [24][25][26].In this Letter we demonstrate the controlled realization of polaritonic spin vortices in an open-access microcavity with a tunable texture, where a top concave mirror creates a zero-dimensional confinement potential for polaritons. The large TE-TM splitting in the open cavity, which consists of two Bragg mirrors separated by an air gap, define...

Tunable Open‐Access Microcavities for Solid‐State Quantum Photonics and Polaritonics

“…Note that there is a short‐focus lens located closely above the sample (blue colored in the inset) for light collection, at the back focal plane of which the Fourier image of k‐space is located. Reproduced with permission . Copyright 2015, APS.…”

“…Dufferwiel et al. reported polariton condensates exhibiting vortex‐like pseudospin textures in a chip‐based open‐access microcavity . A combined effect of the confinement potential created by the concave mirror and the spin–orbit coupling induced by the large TE–TM splitting results in a lifting of degeneracy of the first excited manifold (corresponding to LG mode with ( p , | l |) = (0, 1)), showing eigenstates of radial/azimuthal spin vortices and hyperbolic‐like spin anti‐vortices ( Figure a).…”

“…The second manifold (corresponding to the degenerated LG modes ( p , | l |) = (1, 0) and (0,2)) also splits under the SO coupling effect, showing different ways of pseudospin winding in the inner core and outer ring of the same mode (Figure b). The effect of strong light–matter coupling was investigated in such systems by modifying the exciton/photon fraction, depending on which the polaritons choose to condense either in spin‐vortex‐like patterns or linearly polarized HG states . Compared to other polaritonic systems exhibiting spin vortices, the open‐access microcavity shows its capability of creating spin vortices in a controllable way, as well as the in situ tunability of spin textures by involving the polaritonic properties.…”

Paramagnetic resonance in spin-polarized disordered Bose-Einstein condensates

“…On the other hand, as opposed to spintronics, using EPs can reduce the dramatic impact of the carrier spin relaxation and decoherence 29–32 . Polariton spin dynamics has been extensively studied in literature 33–36 , although many issues remain undiscovered.…”

Pulse, polarization and topology shaping of polariton fluids

“…93 A circular chain containing 8 vortices of the same charge was generated with a Laguerre-Gauss beam, paving the way for more experiments involving self-arranged and same-sign vortex lattices. Other recent advances on the field include the generation of unconventional states, such as polarization textures corresponding to spin vortices in open-cavity polaritons, 94 or exotic topologies (e.g., those referred to as generalized skyrmions in the previous section) under confined nonresonant 95 and imprinted resonant 18 excitation dynamics. Intriguing 2D+t topological strings have been associated to the half-vortex precession, together with pair generation phenomena at high density.…”