Weak lasing in one-dimensional polariton superlattices

Abstract

Bosons with finite lifetime exhibit condensation and lasing when their influx exceeds the lasing threshold determined by the dissipative losses. In general, different one-particle states decay differently, and the bosons are usually assumed to condense in the state with the longest lifetime. Interaction between the bosons partially neglected by such an assumption can smear the lasing threshold into a threshold domain-a stable lasing manybody state exists within certain intervals of the bosonic influxes. This recently described weak lasing regime is formed by the spontaneously symmetry breaking and phase-locking self-organization of bosonic modes, which results in an essentially manybody state with a stable balance between gains and losses. Here we report, to our knowledge, the first observation of the weak lasing phase in a one-dimensional condensate of exciton-polaritons subject to a periodic potential. Real and reciprocal space photoluminescence images demonstrate that the spatial period of the condensate is twice as large as the period of the underlying periodic potential. These experiments are realized at room temperature in a ZnO microwire deposited on a silicon grating. The period doubling takes place at a critical pumping power, whereas at a lower power polariton emission images have the same periodicity as the grating.weak lasing | superlattice | polariton | condensate | symmetry breaking T he application of artificial periodic potentials to electrons and photons causes a rich variety of phenomena, from electronic minibands in semiconductor superlattices to characteristic stop bands in photonic crystals (1-4). These phenomena form the basis for further developments of optoelectronics. Cavity polaritons (5, 6) (quasi-particles formed by the strong coupling of confined photons with excitons) attracted much attention in recent years due to the remarkable coherent effects linked to their half-matter, half-light nature (7-11). As a result, a new area of physics at the boundary between solid-state physics and photonics has emerged.Experiments on spatially inhomogeneous polariton condensation are usually interpreted assuming that all one-particle states have the same lifetime (12, 13). Lifting off this assumption leads to the prediction (14) of the "weak lasing" state of interacting polaritons: a type of condensate stabilized by the spontaneous reduction of the symmetry rather than by the dissipation nonlinearities due to, e.g., reservoir depletion. In this work we report, to our knowledge, the first experimental observation of room-temperature polariton condensation in 1D superlattices, which brings clear evidence for the weak lasing state.The polariton superlattice was assembled using a ZnO microrod with a hexagonal cross-section: a natural whispering gallery resonator to efficiently confine exciton-polaritons (15, 16). Setting the microrod on a silicon slice with periodically arranged channels (Fig. 1) allowed us to avoid the intrinsic structural diffraction typical for the structures with periodic patterns ...

Interacting quantum fluid in a polariton Chern insulator

“…One should notice, however, than in lattices the formation of gap solitons much more favored than the formation of a homogeneous condensate in the ground state 56,57 because of the higher overlap of the negative-mass states and a longer lifetime of states with antisymetric wave functions 58 . Similarly, the slow spin relaxation in the excitonic reservoir makes it difficult to achieve equilibrium between the two spin sub-systems, and prevents the observation of the predicted spin-Meissner effect 59 .…”

Optically trapped polariton condensates as semiclassical time crystals

“…Polariton-polariton interaction plays a crucial role here, as it can lift occasional degeneracy of the state, occupied by the driven condensate, and spontaneously break either translational [17], spatial inversion [18] or parity symmetry [19]. Moreover, polariton-polariton interaction, supplemented with dissipative coupling, is sufficient for condensate stabilization in the weak lasing regime [18].…”

Controllable high-speed polariton waves in a PT-symmetric lattice

“…A recent experimental work [41] demonstrates that in the non-PT-symmetry scenario only one of the two states has been observed in one measurement when the pump intensity is just above the threshold, which agrees very well with our numerical finding. Notice that when the pump intensity is strong the phase transition of polariton condensates from p =  k a x state to the ground state can also be observed [33,42]. Previously, it has been mentioned that even in the PT-symmetric case the eigenenergies can become complex when the ratio of the amplitudes of the imaginary and real potentials exceeds a certain threshold value [5].…”