Optical orientation, polarization pinning, and depolarization dynamics in optically confined polariton condensates

Abstract

We investigate the optical orientation, polarization pinning, and depolarization of optically confined semiconductor exciton-polariton condensates. We perform a complete mapping of the condensate polarization as a function of incident nonresonant excitation polarization and power. We utilize a ring-shaped excitation pattern to generate an exciton-induced potential that spatially confines polariton condensates into a single mode. We observe that formation of circular polarization in the condensate persists even for a weakly cocircularly polarized pump. By varying the excitation ring diameter we realize a transition from the condensate polarization being pinned along the coordinate-dependent cavity-strain axes, to a regime of zero degree of condensate polarization. Analysis through the driven-dissipative stochastic Gross-Pitaevskii equation reveals that this depolarization stems from a competition between sample induced in-plane polarization splitting and the condensate-reservoir overlap. An increase in the role of the latter results in weakening of the condensate fixed-point phase space attractors, and enhanced random phase space walk and appearance of limit cycle trajectories, reducing the degree of time-integrated polarization.

All-Optical Linear-Polarization Engineering in Single and Coupled Exciton-Polariton Condensates

“…The direction of the effective magnetic field is controlled by the angle of our elliptical trap, θ min , which consequently rotates the condensate pseudospin in the Interestingly, in a recent experiment 32 we observed condensation into the spin ground state of a circular trap, where the fine structure splitting originated from the cavity birefringence Ω bir (r). This meant that the condensate pseudospin stabilized parallel to the magnetic field S Ω bir (r).…”

“…1(c,d)] and reciprocal [Fig. 1(e)] space, and record the time-and space-averaged polarization of the PL by simultaneously detecting all polarization components 32 .…”

“…Under nonresonant excitation in inorganic semiconductors, spin transfer from the pumping laser to the condensate is possible by using an elliptically polarized beam which creates a spin-imbalanced polariton gain (i.e., op-tical orientation of excitons) 6,32 . This allows generating condensates of high degree of circular polarization aligned with the pump.…”

“…This allows generating condensates of high degree of circular polarization aligned with the pump. However, the linearly polarized polariton modes experience isotropic gain, making them insensitive to the linear polarization details of the nonresonant excitation source 33,34 except in the presence of cavity strain and birefringence 32,[35][36][37][38][39] or engineered anisotropic cavities 40,41 . The same also applies for VCSELs, where the linear polarization of the emission is engineered by etching asymmetric masks 42,43 or electrodes 44 , heating 45 , or applying mechanical stress 26 .…”

Polariton spin jets through optical control

“…The optical selection rules enable direct measurement of the spinor polariton structure via standard polarization resolved imaging of photoluminescence (PL). Conversely, one can excite directly polariton spin states using polarized resonant lasers [19,23], or indirectly using polarized non-resonant lasers [9,14,24].…”