Dynamics of polaritons resonantly created at the upper polariton branch

We have studied the polariton relaxation dynamics in a CdTe microcavity at low temperatures after resonant excitation into the upper polariton branch (UPB). Initially, we have set a negative exciton–cavity detuning, such that the energy difference between the two polariton branches coincides with that of an LO phonon. Our experimental results reveal a sublinear dependence of the integrated emission from the lower polariton branch (LPB) with excitation power. This evidences not only an inefficient LO phonon mediated relaxation from the UPB to the LPB but also a substantial inhibition of polariton relaxation along the LPB. After that, we have progressively reduced the negative detuning, approaching the exciton–cavity resonance. Under these conditions it is possible to observe a nonlinear emission arising from K0 LPB-states similar to that observed after nonresonant excitation. Marked oscillations are present in the time evolution traces, with a period that does not depend on excitation power or detuning.     

Role of surface plasmon polaritons in anomalous transmission of an electromagnetic wave through two arrays with subwavelength slits

The anomalously large transmission of an electromagnetic wave through structures consisting of two periodic arrays of subwavelength slits in films has been investigated. The conditions ensuring zero transmittance of this system have been determined. The role of surface plasmon polaritons in transmission anomalies has been analyzed. An analysis of the systems consisting of three arrays of slits has revealed specific features of the transmittance that are independent of the number of slits. It has been demonstrated that, at a wavelength corresponding to the excitation of a surface plasmon polariton in the gap between two periodic arrays of subwavelength slits, the transmittance is zero (i.e., transmission is suppressed). The investigation has been carried out using numerical simulations with the Fourier modal method.     

极化激元(polaritons)与拉曼散射

在给出介质中的光（电磁）波与极化波混合作用而得出的极化激元方程。极化激元色散方程之后又讨论了相应的物理意义及相关的物理问题；获得极化激元的实验方法。接着还介绍和讨论了极化激元的拉曼散射。     

Propagating wave packets and quantized currents in coherently driven polariton superfluids

We study the properties of propagating polariton wave packets and their connection to the stability of doubly charged vortices. Wave-packet propagation and related photoluminescence spectra exhibit a rich behavior dependent on the excitation regime. We show that, because of the nonquadratic polariton dispersion, doubly charged vortices are stable only when initiated in wave packets propagating at small velocities. Vortices propagating at larger velocities, or those imprinted directly into the polariton optical parametric oscillator signal and idler, are unstable to splitting.     

晶格振动对表面电磁波-激子耦合系统色散性质的影响

局域在介质表面附近的电磁波与介质中的元激发相互耦合形成另一类的元激发——表面极化激元(polariton),它与半导体的许多光学性质都有关。本文研究了介质中的品格振动对表面电磁波-激子耦合系统色散性质的影响,仔细探讨了共振吸收区附近色散曲线的奇异性质,并对其产生的原因做了分析和讨论。     

A train of bright and dark-rogue wave solitons in a polariton fluid with inhomogeneous strength interaction

We solve using the similarity transformation method a one-dimensionless driven-dissipative nonlinear Schrödinger equation to explore the dynamics of the rogue wave solitons generated in a polariton fluid. Under resonant excitation, we predict the existence of the bright and the dark-rogue waves solitons by varying the external pump source parameter. By considering, a time periodic polariton–polariton interaction and adjusting its frequency, the rogue wave soliton trains occur in a polariton fluid. In addition we observe that, the amplitude of the pump power is responsible to the formation of a the train of the bright and the dark rogue waves solitons.     

Polariton laser using single micropillar GaAs-GaAlAs semiconductor cavities

Polariton lasing is demonstrated on the zero-dimensional states of single GaAs/GaAlAs micropillar cavities. Under nonresonant excitation, the measured polariton ground-state occupancy is found as large as 10(4). Changing the spatial excitation conditions, competition between several polariton lasing modes is observed, ruling out Bose-Einstein condensation. When the polariton state occupancy increases, the emission blueshift is the signature of self-interaction within the half-light half-matter polariton lasing mode.     

基于耦合场量子受激拉曼散射的太赫兹波辐射

使用两块长度各为65 mm的MgO:LiNbO3和无掺杂LiNbO3晶体,以1064nm的Q开关Nd:YAG激光器作为抽运光源,在12 mJ/pulse的抽运光能量下得到频率范围为0.34～2.90 THz的电磁辐射.分析表明,激光入射使LiNbO3晶体中具有电磁特性的横光学声子可以和入射光子形成耦合场量子.作为一种电磁特性的元激发,LINbO3晶体的耦合场量子的辐射场频率覆盖部分太赫兹频段范围,并可通过耦合场量子受激拉曼散射过程辐射THz波.根据耦合场量子辐射理论,通过分析晶体的耦合场量子色散特性曲线,可以确定该晶体能否辐射THz波及其带宽范围.     

An analog of the Migdal-Kohn singularity and the radiation width of the high-frequency branch of the polariton spectrum for a bounded crystal of the <Emphasis Type="Italic">J</Emphasis>-aggregate type

The excitation spectra of crystalline ensembles of coherently emitting interacting quantum electric dipole oscillators are investigated. The system of dynamic equations derived for a one-dimensional crystal of the J-aggregate type can be used in various limiting cases for studying optical photons as well as X-ray and gamma quanta. An exact analytic solution to the dispersion equation is obtained for polaritons (mixed states of Frenkel excitons and transverse photons). It is shown that the high-frequency polariton branch with anomalously high radiation broadening has the limiting wave vector corresponding to the spectral edge not because the broadening becomes comparable to the frequency (as was generally accepted earlier), but due to smooth joining of this polariton branch with the other (nonphysical) branch determined from the dispersion equation. At this point, the derivative of the dispersion curve goes to infinity, which is an analog of the well-known Migdal-Kohn singularity in the phonon spectra of metals. It is shown that the low-frequency polariton branch also exhibits slight broadening due to the fact that the proper radiation width is taken into account exactly.     

Dispersion polaritons on metallized surfaces of optically uniaxial crystals

We have constructed a theory of dispersion polaritons (localized electromagnetic waves) on arbitrarily oriented metallized surfaces of optically uniaxial crystals. The domain of existence of polaritons is defined by the following inequalities for permittivities ε_o and ε_e of the crystal and the angle θ between the optical axis and the surface: ?ε_etan²θ < ε_o < 0. Thus, polaritons exist only in the range of wave frequencies ω ensuring negative values of ε_o(ω) for ε_e > 0. The frequency boundaries of this region are specified for the case when the ε_o(ω) dependence corresponds to the model of a single polar excitation. The azimuthal orientation φ of the optical axis projection onto the surface does not appear in the criterion for polariton existence, but affects (together with angle θ) its main dispersion characteristics, such as the refractive index and partial wave localization parameters. This effect is analytically described in detail. Anomalies in the behavior of polariton parameters are studied in the vicinity of the boundaries of the domain of its existence, where the wave fields are especially sensitive to variations in the angles θ and φ. It is shown that a polariton in the plane of propagation (sagittal plane) passing through the optical axis is transformed into a one-partial bulk wave satisfying the boundary conditions. Accordingly, the wave branch under investigation for close orientations (when the optical axis forms a small angle with the sagittal plane) describes deeply penetrating (quasi-bulk) polaritons.     

High light transmission through thin absorptive corrugated films

The enhancement of light transmittance through periodically relief thin absorptive film at surface plasmon polariton excitation conditions, as a function of relief interrelation, was considered theoretically. Our calculation of transmittance-reflectance through periodically relief thin absorptive film was performed in the framework of differential formalism. There are two basic relief interrelation forms, namely, correlated and anticorrelated ones. The obtained spectral and angular dependencies demonstrate an essential increase of surface plasmon polariton peaks in the case of anticorrelated corrugation of film in comparison with the correlated ones.     

Virtual excitation type surface polaritons on anisotropic media

We discuss the nature of a new type of surface polariton which occurs on anisotropic media, involving a photon coupled to a surface virtual excitation. Dispersion curves are calculated for α-quartz, where both real excitation type and virtual excitation type surface polaritons are predicted. The dispersion curves for virtual excitation surface polaritons are found to remain at small wavevector, and the endpoints of the dispersion curves terminate on the bulk polariton dispersion curves in the two media. The virtual excitation surface polaritons which occur on gyromagnetic and gyrodielectric media are also noted.     

Manipulating atomic coherence and interference in a coupled atom-cavity system

Collective coupling of multiple atoms with a cavity mode produces two normal modes that are separated in energy by Vacuum Rabi splitting. We show that quantum coherence and interference can be produced by a control laser that couples the atoms confined in the cavity mode from free space, which leads to suppression of the normal mode excitation, or polariton excitation of the cavity-atom system. The control laser splits the normal mode of the cavity-atoms system and opens two excitation channels. The destructive quantum interference between the two channels renders the cavity-atoms system opaque to the light coupled into the cavity mode. We demonstrate suppression of the normal mode (polariton) excitation by the destructive quantum interference in an experiment with cold Rb atoms confined in an optical cavity.     

Theory of nonlinear excitation of surface polaritons in lossy media

The purpose of this paper is to study the nonlinear excitation of surface polaritons taking fully into account the damping of the active medium and the finite cross-section of the nonlinear polarization on the interface. This problem is solved using the guided wave calculation techniques where the EM field at the surface polariton frequency is expanded over a complete set of normal modes of the unperturbed interface. Using a “table method” we find that this set includes one guided mode, which is the surface polariton mode, and two classes of radiation modes. The expressions of all these modes are derived and interpreted physically. We then get the expression of the EM field excited at the surface polariton frequency inside and outside the pumped region and show that, in the general case, it is a mixture of all these normal modes. The end of the paper is mainly devoted to the study of the surface term occurring in the expression of the EM field at the surface polariton frequency: we point out the existence of a resonance phenomenon with two kinds of surface polariton modes: the “spatial” one and the “temporal” one. The corresponding dispersion curves, or resonance curves, are given and it is explained how each of them can be obtained experimentally.     

Polariton luminescence in high-purity layers of AlGaAs solid solutions

An additional polariton emission line caused by a change in the polariton energy distribution function owing to the exciton-exciton scattering is observed experimentally. The energy shift of this line and the variation in its intensity with increasing excitation power agree well with the results of calculations performed in the framework of the theoretical model proposed by Bisti [Fiz. Tverd. Tela 18, 1056 (1976)].     

Optical polariton properties in ZnSe-based planar and pillar structured microcavities

Strong coupling is demonstrated in monolithic ZnSe-based microcavities. Under nonresonant excitation the polariton dispersion has been investigated in dependence on the photon-exciton detuning for different excitation densities at low temperatures. For zero detuning indications of a polariton lasing threshold are observed like a k-space and energy dispersion narrowing of the lower polariton branch with increasing excitation density. Furthermore, it is observed that this effect is hampered for measurements at negative detunings as a result of the less effective polariton relaxation to the ground state. Latter results in the formation of a discrete polariton distribution at finite k values as known for the polariton bottleneck. In order to investigate the influence of a three-dimensional optical confinement on the polariton relaxation, pillar structured microcavities were fabricated. The formation of discrete polariton states in the k-space distribution is observed. Furthermore, indications for a softening of the k-conservation arising from the structural confinement are found leading to a more effective polariton relaxation. This process would be beneficial for the realization of efficient polariton lasing processes.     

Energy relaxation of excitonlike polaritons in semiconductor microcavities: Effect on the parametric scattering of polaritons

Polariton emission in GaAs-based microcavities has been studied under variable conditions, which made it possible to excite (a) polaritons from the upper polariton branch and hot free polaritons and electrons, (b) polaritons from the lower polariton branch (LPB) and localized excitons, and (c) the mixed system. Variation of the excitation conditions leads to substantial differences in the energy distributions of polaritons and in the temperature dependences of polariton emission. It is established that the energy relaxation of resonantly excited LPB polaritons via polariton and localized exciton states at liquid helium temperatures is ineffective. Instead, the relaxation bottleneck effect is suppressed with increasing temperature by means of exciton delocalization (due to thermal excitation by phonons). The most effective mechanism of relaxation to the LPB bottom is via scattering of delocalized excitons on hot free carriers. It is found that the slow energy relaxation of polaritons excited below the free exciton energy can be significantly accelerated at low temperatures by means of additional weak generation of hot excitons and, especially, hot electrons. This acceleration of the energy relaxation of polaritons by means of additional overbarrier photoexcitation sharply decreases the barrier for stimulated parametric scattering of polaritons excited at an LPB inflection point. Therefore, additional illumination can be used to control the polariton-polariton scattering.     

Stimulated parametric scattering of excitonic polaritons in planar GaAs microcavities: Distinctive feature of QW electric field

Instabilities in the electric field at the QW in the active region of a GaAs based microcavity have been investigated under the resonance excitation near the inflection point of the low polariton (LP) dispersion curve with the use of four wave mixing technique. The electric field jump due to an LP bistability has been found to precede the development of a stimulated parametric scattering of LPs. The latter has been found to develop with a delay of a few hundreds ps from the beginning of the excitation pulse. These results are in qualitative agreement with hard regime of excitation of the stimulated parametric LP scattering predicted recently.     

Spin dynamics of a vortical condensate of exciton polaritons in a GaAs microcavity

The temporal dynamics of a spinor exciton-polariton condensate in a high-quality anisotropic GaAs microcavity under pulsed resonant excitation with light possessing a nonzero orbital angular momentum is investigated. The phenomenon of spatial separation of the spin components of the polariton condensate upon pumping with a coherent superposition of two beams with opposite circular polarizations and orbital angular momenta is observed. The key factors for the observation of this effect are the lateral anisotropy of the microcavity that causes a splitting between the linear components of the polariton ground state and the occurrence of opposite orbital angular momenta for the two spin components of the condensate. The experimental results are in qualitative agreement with the theoretical model of the phenomenon developed in JETP Lett. 104, 827 (2016).     

Controlled spin pattern formation in multistable cavity–polariton systems

Theoretical studies are performed of planar cavity–polariton systems under resonant optical excitation. We show that if the cavity is spatially anisotropic, the polariton spin is highly sensitive to the pump polarization direction, which can be used to modulate the circular polarization of the output light. In particular, when the right- and left-circular components of the incident wave have equal intensities and mutually opposite angular momenta, the pump has strictly linear yet angle-dependent polarization and as such brings about a periodic angular variation of the polariton spin. Free motion of polaritons is the other factor determining the shape of the cavity-field distribution. Such externally driven and highly tunable spin patterns represent a counterpart of spin shaping in nonresonantly excited Bose–Einstein condensates of cavity polaritons.