Semiconductor Microcavities Research Articles

(Cd,Zn,Mg)Te-based microcavity on MgTe sacrificial buffer: Growth, lift-off, and transmission studies of polaritons

Opaque substrates precluded, so far, transmission studies of II-VI semiconductor microcavities. This work presents the design and molecular beam epitaxy growth of semimagnetic (Cd,Zn,Mn)Te quantum wells embedded into a (Cd,Zn,Mg)Te-based microcavity, which can be easily separated from the GaAs substrate. Our lift-off process relies on the use of a MgTe sacrificial layer which stratifies in contact with water. This allowed us to achieve a II-VI microcavity prepared for transmission measurements. We evidence the strong light-matter coupling regime using photoluminescence, reflectivity, and transmission measurements at the same spot on the sample. By comparing a series of reflectance spectra before and after lift-off, we prove that the microcavity quality remains high. Thanks to Mn content in quantum wells we show the giant Zeeman splitting of semimagnetic exciton-polaritons in our transmitting structure.

Dynamics in terahertz semiconductor microcavity: quantum noise spectra

We investigate the physics of an optical semiconductor microcavity containing a coupled double quantum well interacting with cavity photons. The photon statistics of the transmitted light by the cavity is explored. We show that the nonlinear interactions in the direct and indirect excitonic modes generate an important squeezing despite the weak nonlinearities. When the strong coupling regime is achieved, the noise spectra of the system is dominated by the indirect exciton distribution. At the opposite, in the weak regime, direct excitons contribute much larger in the noise spectra.

Giant optical nonlinearities from Rydberg excitons in semiconductor microcavities

The realization of exciton polaritons—hybrid excitations of semiconductor quantum well excitons and cavity photons—has been of great technological and scientific significance. In particular, the short-range collisional interaction between excitons has enabled explorations into a wealth of nonequilibrium and hydrodynamical effects that arise in weakly nonlinear polariton condensates. Yet, the ability to enhance optical nonlinearities would enable quantum photonics applications and open up a new realm of photonic many-body physics in a scalable and engineerable solid-state environment. Here we outline a route to such capabilities in cavity-coupled semiconductors by exploiting the giant interactions between excitons in Rydberg states. We demonstrate that optical nonlinearities in such systems can be vastly enhanced by several orders of magnitude and induce nonlinear processes at the level of single photons.

One- and two-dimensional modes in the complex Ginzburg-Landau equation with a trapping potential.

We propose a new mechanism for the stabilization of confined modes in lasers and semiconductor microcavities holding exciton-polariton condensates, with spatially uniform linear gain, cubic loss, and cubic self-focusing or defocusing nonlinearity. We demonstrated that the commonly known background instability driven by the linear gain can be suppressed by a combination of a harmonic-oscillator trapping potential and effective diffusion. Systematic numerical analysis of one- and two-dimensional (1D and 2D) versions of the model reveals a variety of stable modes, including stationary ones, breathers, and quasi-regular patterns filling the trapping area in the 1D case. In 2D, the analysis produces stationary modes, breathers, axisymmetric and rotating crescent-shaped vortices, stably rotating complexes built of up to 8 individual vortices, and, in addition, patterns featuring vortex turbulence. Existence boundaries for both 1D and 2D stationary modes are found in an exact analytical form, and an analytical approximation is developed for the full stationary states.

Photonic-crystal exciton-polaritons in monolayer semiconductors

Semiconductor microcavity polaritons, formed via strong exciton-photon coupling, provide a quantum many-body system on a chip, featuring rich physics phenomena for better photonic technology. However, conventional polariton cavities are bulky, difficult to integrate, and inflexible for mode control, especially for room-temperature materials. Here we demonstrate sub-wavelength-thick, one-dimensional photonic crystals as a designable, compact, and practical platform for strong coupling with atomically thin van der Waals crystals. Polariton dispersions and mode anti-crossings are measured up to room temperature. Non-radiative decay to dark excitons is suppressed due to polariton enhancement of the radiative decay. Unusual features, including highly anisotropic dispersions and adjustable Fano resonances in reflectance, may facilitate high temperature polariton condensation in variable dimensions. Combining slab photonic crystals and van der Waals crystals in the strong coupling regime allows unprecedented engineering flexibility for exploring novel polariton phenomena and device concepts.

Lieb polariton topological insulators

We predict that the interplay between the spin-orbit coupling, stemming from the TE-TM energy splitting, and the Zeeman effect in semiconductor microcavities supporting exci- ton-polariton quasi-particles results in the appearance of unidirectional linear topological edge states when the top microcavity mirror is patterned to form a truncated dislocated Lieb lattice of cylindrical pillars. Periodic nonlinear edge states are found to emerge from the linear ones. They are strongly localized across the interface and they are remarkably robust in comparison to their counterparts in hexagonal lattices. Such robustness makes possible the existence of nested unidirectional dark solitons that move steadily along the lattice edge.

Polariton solitons and nonlinear localized states in a one-dimensional semiconductor microcavity.

This paper presents numerical studies of cavity polariton solitons (CPSs) in a resonantly pumped semiconductor microcavity with an imbedded spatial defect. In the bistable regime of the well-known homogeneous polariton condensate, with proper incident wave vector and pump strength, bright and/or dark cavity solitons can be found in the presence of a spatially confined potential. The minimum pump strength required to observe the CPSs or nonlinear localized states in this parametric pump scheme is therefore reported.

Unconventional photon blockade from bimodal driving and dissipations in coupled semiconductor microcavities

We propose an unconventional photon blockade scheme in coupled semiconductor microcavities embedded in a nonlinear Kerr medium in the presence of photon leakage and bimodal driving on two cavity modes, which consists of two spatially overlapping single-mode semiconductor cavities with cross-Kerr nonlinearity and two-photon tunneling. A detailed analysis is derived for the exact optimal conditions for strong photon antibunching with weak Kerr nonlinearities. It is very important to find the transition of the structures of the solution for the optimal detuning from the quartic equation to the cubic equation when changing the two complex driving fields appropriately. The transition originates from the second driving field that compensates the numbers of interference paths reaching a two-photon state. This unconventional photon blockade can be realized by coupled photonic crystal cavities filled with a nonlinear Kerr medium. This implies that nonlinear Kerr medium systems can be used to generate tunable single-photon sources by tuning the strength and relative phase of two complex driving fields under weak Kerr nonlinearity.

Quantum exciton-polariton networks through inverse four-wave mixing

We demonstrate the potential of quantum operation using lattices of exciton-polaritons in patterned semiconductor microcavities. By introducing an inverse four-wave mixing scheme acting on localized modes, we show that it is possible to develop non-classical correlations between individual condensates. This allows a concept of quantum exciton-polariton networks, characterized by the appearance of multimode entanglement even in the presence of realistic levels of dissipation.

Evolution of Temporal Coherence in Confined Exciton-Polariton Condensates.

We study the influence of spatial confinement on the second-order temporal coherence of the emission from a semiconductor microcavity in the strong coupling regime. The confinement, provided by etched micropillars, has a favorable impact on the temporal coherence of solid state quasicondensates that evolve in our device above threshold. By fitting the experimental data with a microscopic quantum theory based on a quantum jump approach, we scrutinize the influence of pump power and confinement and find that phonon-mediated transitions are enhanced in the case of a confined structure, in which the modes split into a discrete set. By increasing the pump power beyond the condensation threshold, temporal coherence significantly improves in devices with increased spatial confinement, as revealed in the transition from thermal to coherent statistics of the emitted light.

Charged Polaron Polaritons in an Organic Semiconductor Microcavity.

We report strong coupling between light and polaron optical excitations in a doped organic semiconductor microcavity at room temperature. Codepositing MoO_{3} and the hole transport material 4, 4^{'}-cyclohexylidenebis[N, N-bis(4-methylphenyl)benzenamine] introduces a large hole density with a narrow linewidth optical transition centered at 1.8eV and an absorption coefficient exceeding 10^{4} cm^{-1}. Coupling this transition to a Fabry-Pérot cavity mode yields upper and lower polaron polariton branches that are clearly resolved in angle-dependent reflectivity with a vacuum Rabi splitting ℏΩ_{R}>0.3 eV. This result establishes a path to electrically control polaritons in organic semiconductors and may lead to increased polariton-polariton Coulombic interactions that lower the threshold for nonlinear phenomena such as polariton condensation and lasing.

Oscillations of the degree of circular polarization in the optical spin Hall effect

AbstractThe optical spin Hall effect appears when elastically scattered exciton polaritons couple to an effective magnetic field inside of quantum wells in semiconductor microcavities. Theory predicts an oscillation of the pseudospin of the exciton polaritons in time. Here, we present a detailed analysis of momentum space dynamics of the exciton polariton pseudospin. Compared to what is predicted by theory, we find a higher modulation of the temporal oscillations of the pseudospin. We attribute the higher modulation to additional components of the effective magnetic field which have been neglected in the foundational theory of the optical spin Hall effect. Adjusting the model by adding non-linear polariton-polariton interactions, we find a good agreement in between the experimental results and simulations.

Quantum fluctuation and nonlinear properties of exciton polaritons in semiconductor microcavities

The impact of quantum fluctuations on the properties of quantum well excitons excited inside 0D semiconductor microcavity possessing strong light confinement is analysed. The analysis takes into account the exciton-exciton repulsion and the presence of a reservoir. Analytical solutions are obtained for the generalized Glauber P-function of the system in the adiabatic limit. Destabilization of the homogeneous nonlinear solution belonging to the lower bistability branch in the presence of quantum noise is predicted.

Nonlinear bifurcation diagrams of the current states of microcavity exciton-polaritons in the lattice

We study nonequilibrium properties of exciton-polaritons in an incoherently driven semiconductor microcavity with an embedded weak-contrast periodic lattice. Within the framework of mean-field theory, we describe nonlinear eigenstates of coherent exciton polaritons having the structure of Bloch waves and identify nonlinear current states at the boundaries of Brillouin zone. We demonstrate a profound modification of the eigenfrequency-momenta bifurcation diagrams of the condensate evoked by exciton-exciton interactions. The discussed phenomenon occurs for the states possessing high degree of symmetry, i.e. in particular, for the states lying at the centre or at the boundary of Brillouin zone.

Photon statistics of semiconductor microcavity polaritons

Quantum statistical properties of the coherently driven semiconductor microcavity are studied. The unique quantum solution for the two-mode system of coupled excitons and photons was obtained in the adiabatic approximation. This solution predicts both bunching and antibunching regimes for the photonic field in the domain of parameters where the single mode polariton approximation fails.

Lasing from lead halide perovskite semiconductor microcavity system.

Organic-inorganic halide perovskite semiconductors are ideal gain media for fabricating laser and photonic devices due to high absorption, photoluminescence (PL) efficiency and low nonradiative recombination losses. Herein, organic-inorganic halide perovskite CH3NH3PbI3 is embedded in the Fabry-Perot (FP) microcavity, and a wavelength-tunable excitonic lasing with a threshold of 12.9 μJ cm-2 and the spectral coherence of 0.76 nm are realized. The lasing threshold decreases and the spectral coherence enhances as the temperature decreases; these results are ascribed to the suppression of exciton irradiative recombination caused by thermal fluctuation. Moreover, both lasing and light emission below threshold from the perovskite microcavity (PM) system demonstrate a redshift with the decreasing temperature. These results provide a feasible platform based on the PM system for the study of light-matter interaction for quantum optics and the development of optoelectronic devices such as polariton lasers.

Quantum phase transition in an effective three-mode model of interacting bosons.

In this work we study an effective three-mode model describing interacting bosons. These bosons can be considered as exciton-polaritons in a semiconductor microcavity at the magic angle. This model exhibits quantum phase transition (QPT) when the parameters of the corresponding Hamiltonian are continuously varied. The properties of the Hamiltonian spectrum (e.g., the distance between two adjacent energy levels) and the phase space structure of the thermodynamic limit of the model are used to indicate QPT. The relation between spectral properties of the Hamiltonian and the corresponding classical frame of the thermodynamic limit of the model is established as indicative of QPT. The average number of bosons in a specific mode and the entanglement properties of the ground state as functions of the parameters are used to characterize the order of the transition and also to construct a phase diagram. Finally, we verify our results for experimental data obtained for a setting of exciton-polaritons in a semiconductor microcavity.

Theory of optically controlled anisotropic polariton transport in semiconductor double microcavities

Exciton polaritons in semiconductor microcavities exhibit many fundamental physical effects, with some of them amenable to being controlled by external fields. The polariton transport is affected by the polaritonic spin-orbit interaction, which is caused by the splitting of transverse-electric and transverse-magnetic (TE-TM) modes. This is the basis for a polaritonic Hall effect, called optical spin Hall effect (OSHE), which is related to the formation of spin/polarization textures in momentum space, determining anisotropic ballistic transport, as well as related textures in real space. Owing to Coulombic interactions between the excitonic components of the polaritons, optical excitation of polaritons can affect the OSHE. We present a theoretical analysis of the OSHE and its optical control in semiconductor double microcavities, i.e. two optically coupled cavities, which are particularly well suited for the creation of polaritonic reservoirs that affect the spin-texture-forming polaritons. The theory is formulated in terms of a set of double-cavity spinor-polariton Gross-Pitaevskii equations. Numerical solutions feature, among other things, a controlled rotation of the spin texture in momentum space. The theory also allows for an identification of the effective magnetic field component that determines the optical control in phenomenological pseudo-spin models in terms of exciton interactions and the polariton density in the second lower polariton branch.

Microscopic optical anisotropy of exciton-polaritons in a GaAs-based semiconductor microcavity

Exciton-polaritons in semiconductor microcavities are ideal for the study of the exciton-light interaction and its dependence on light polarization. In this work, we report on the optical response and the dependence on polarization of a polariton microcavity using microreflectance anisotropy spectroscopy ($\ensuremath{\mu}$-RAS) with a spatial resolution of $10.0\ifmmode\times\else\texttimes\fi{}10.0\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}{\mathrm{m}}^{2}$. We have found that, in contrast to optical reflection, the $\ensuremath{\mu}$-RAS spectra are quite inhomogeneous along the microcavity surface. We demonstrate the existence of microscopic local domains with differences in optical anisotropy of up to $20%$ within $100\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}$. These variations are independent of the detuning between the optical and excitonic resonances, which in our sample is close to 0 meV. The $\ensuremath{\mu}$-RAS line shape can be understood by using a model based on the anisotropic strain fields induced at the interfaces of the microcavity. The model agrees quite well with the experimental results and allows us to quantify the split of the energy levels of the exciton-polariton branches induced by the local break of symmetry at the microcavity interfaces.

Topological order and thermal equilibrium in polariton condensates.

The Berezinskii-Kosterlitz-Thouless phase transition from a disordered to a quasi-ordered state, mediated by the proliferation of topological defects in two dimensions, governs seemingly remote physical systems ranging from liquid helium, ultracold atoms and superconducting thin films to ensembles of spins. Here we observe such a transition in a short-lived gas of exciton-polaritons, bosonic light-matter particles in semiconductor microcavities. The observed quasi-ordered phase, characteristic for an equilibrium two-dimensional bosonic gas, with a decay of coherence in both spatial and temporal domains with the same algebraic exponent, is reproduced with numerical solutions of stochastic dynamics, proving that the mechanism of pairing of the topological defects (vortices) is responsible for the transition to the algebraic order. This is made possible thanks to long polariton lifetimes in high-quality samples and in a reservoir-free region. Our results show that the joint measurement of coherence both in space and time is required to characterize driven-dissipative phase transitions and enable the investigation of topological ordering in open systems.