Semiconductor quantum dots in cavities are promising single-photon sources. Here, we present a path to deterministic operation, by harnessing the intrinsic linear dipole in a neutral quantum dot via ...phonon-assisted excitation. This enables emission of fully polarized single photons, with a measured degree of linear polarization up to 0.994±0.007, and high population inversion-85% as high as resonant excitation. We demonstrate a single-photon source with a polarized first lens brightness of 0.50±0.01, a single-photon purity of 0.954±0.001, and single-photon indistinguishability of 0.909±0.004.
The scaling of optical quantum technologies requires efficient, on-demand sources of highly indistinguishable single photons. Semiconductor quantum dots inserted into photonic structures are ...ultrabright single-photon sources, yet the indistinguishability is limited by charge noise. Parametric downconversion sources provide highly indistinguishable photons but are operated at very low brightness to maintain high single-photon purity. To date, no technology has provided a bright source generating near-unity indistinguishability and pure single photons. Here, we report such devices made of quantum dots in electrically controlled cavities. Application of an electrical bias on the deterministically fabricated structures is shown to strongly reduce charge noise. Under resonant excitation, an indistinguishability of 0.9956 ± 0.0045 is demonstrated with g(2) (0) = 0.0028 ± 0.0012. The photon extraction of 65% and measured brightness of 0.154 ± 0.015 make this source 20 times brighter than any source of equal quality. This new generation of sources opens the way to new levels of complexity and scalability in optical quantum technologies.
Orbital angular momentum (OAM) carried by helical light beams is an unbounded degree of freedom that offers a promising platform in modern photonics. So far, integrated sources of coherent light ...carrying OAM are based on resonators whose design imposes a single, non-tailorable chirality of the wavefront (that is, clockwise or counterclockwise vortices). Here we propose and demonstrate the realization of an integrated microlaser where the chirality of the wavefront can be optically controlled. Importantly, the scheme that we use, based on the optical breaking of time-reversal symmetry in a semiconductor microcavity, can be extended to different laser architectures, thus paving the way to the realization of a new generation of OAM microlasers with tunable chirality.Based on optically breaking time-reversal symmetry by spin polarizing a gain medium with a circularly polarized optical pump, an integrated scheme for controlling the chirality of orbital angular momentum lasing is demonstrated.
The extraordinary electronic properties of Dirac materials, the two-dimensional partners of Weyl semimetals, arise from the linear crossings in their band structure. When the dispersion around the ...Dirac points is tilted, one can predict the emergence of intricate transport phenomena such as modified Klein tunneling, intrinsic anomalous Hall effects, and ferrimagnetism. However, Dirac materials are rare, particularly with tilted Dirac cones. Recently, artificial materials whose building blocks present orbital degrees of freedom have appeared as promising candidates for the engineering of exotic Dirac dispersions. Here we take advantage of the orbital structure of photonic resonators arranged in a honeycomb lattice to implement photonic lattices with semi-Dirac, tilted, and, most interestingly, type-III Dirac cones that combine flat and linear dispersions. Type-III Dirac cones emerge from the touching of a flat and a parabolic band when synthetic photonic strain is introduced in the lattice, and they possess a nontrivial topological charge. This photonic realization provides a recipe for the synthesis of orbital Dirac matter with unconventional transport properties and, in combination with polariton nonlinearities, opens the way to study Dirac superfluids in topological landscapes.
Two-dimensional lattices of coupled micropillars etched in a planar semiconductor microcavity offer a workbench to engineer the band structure of polaritons. We report experimental studies of ...honeycomb lattices where the polariton low-energy dispersion is analogous to that of electrons in graphene. Using energy-resolved photoluminescence, we directly observe Dirac cones, around which the dynamics of polaritons is described by the Dirac equation for massless particles. At higher energies, we observe p orbital bands, one of them with the nondispersive character of a flatband. The realization of this structure which holds massless, massive, and infinitely massive particles opens the route towards studies of the interplay of dispersion, interactions, and frustration in a novel and controlled environment.
We report on the engineering of a nondispersive (flat) energy band in a geometrically frustrated lattice of micropillar optical cavities. By taking advantage of the non-Hermitian nature of our ...system, we achieve bosonic condensation of exciton polaritons into the flat band. Because of the infinite effective mass in such a band, the condensate is highly sensitive to disorder and fragments into localized modes reflecting the elementary eigenstates produced by geometric frustration. This realization offers a novel approach to studying coherent phases of light and matter under the controlled interplay of frustration, interactions, and dissipation.
Conduction through materials crucially depends on how ordered the materials are. Periodically ordered systems exhibit extended Bloch waves that generate metallic bands, whereas disorder is known to ...limit conduction and localize the motion of particles in a medium1,2. In this context, quasiperiodic systems, which are neither periodic nor disordered, demonstrate exotic conduction properties, self-similar wavefunctions and critical phenomena3. Here, we explore the localization properties of waves in a novel family of quasiperiodic chains obtained when continuously interpolating between two paradigmatic limits4: the Aubry–André model5,6, famous for its metal-to-insulator transition, and the Fibonacci chain7,8, known for its critical nature. We discover that the Aubry–André model evolves into criticality through a cascade of band-selective localization/delocalization transitions that iteratively shape the self-similar critical wavefunctions of the Fibonacci chain. Using experiments on cavity-polariton devices, we observe the first transition and reveal the microscopic origin of the cascade. Our findings offer (1) a unique new insight into understanding the criticality of quasiperiodic chains, (2) a controllable knob by which to engineer band-selective pass filters and (3) a versatile experimental platform with which to further study the interplay of many-body interactions and dissipation in a wide range of quasiperiodic models.The localization properties of waves in the quasiperiodic chains described by the Aubry–André model and Fibonacci model are investigated. Passing from one model to the other, the system develops a cascade of delocalization transitions.
We experimentally explore the dynamical optical hysteresis of a semiconductor microcavity as a function of the sweep time. The hysteresis area exhibits a double power law decay due to the influence ...of fluctuations, which trigger switching between metastable states. Upon increasing the average photon number and approaching the thermodynamic limit, the double power law evolves into a single power law. This algebraic behavior characterizes a dissipative phase transition. Our findings are in good agreement with theoretical predictions for a single mode resonator influenced by quantum fluctuations, and the present experimental approach is promising for exploring critical phenomena in photonic lattices.
Bright sources of indistinguishable single photons are strongly needed for the scalability of quantum information processing. Semiconductor quantum dots are promising systems to build such sources. ...Several works demonstrated emission of indistinguishable photons while others proposed various approaches to efficiently collect them. Here we combine both properties and report on the fabrication of ultrabright sources of indistinguishable single photons, thanks to deterministic positioning of single quantum dots in well-designed pillar cavities. Brightness as high as 0.79±0.08 collected photon per pulse is demonstrated. The indistinguishability of the photons is investigated as a function of the source brightness and the excitation conditions. We show that a two-laser excitation scheme allows reducing the fluctuations of the quantum dot electrostatic environment under high pumping conditions. With this method, we obtain 82±10% indistinguishability for a brightness as large as 0.65±0.06 collected photon per pulse.
The coupling of two macroscopic quantum states through a tunnel barrier gives rise to Josephson phenomena1 such as Rabi oscillations2, the a.c. and d.c. effects3, or macroscopic self-trapping, ...depending on whether tunnelling or interactions dominate4. Nonlinear Josephson physics was rst observed in superuid helium5 and atomic condensates6,7, but it has remained inaccessible in photonic systems because it requires large photonphoton interactions. Here we report on the observation of nonlinear Josephson oscillations of two coupled polariton condensates conned in a photonic molecule formed by two overlapping micropillars etched in a semiconductor microcavity8. At low densities we observe coherent oscillations of particles tunnelling between the two sites.
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