Polariton Lasing Research Articles

Polariton lasing in high-quality selenide-based micropillars in the strong coupling regime

We have designed and fabricated all-epitaxial ZnSe-based optical micropillars exhibiting the strong coupling regime between the excitonic transition and the confined optical cavity modes. At cryogenic temperatures, under non-resonant pulsed optical excitation, we demonstrate single transverse mode polariton lasing operation in the micropillars. Owing to the high quality factors of these microstructures, the lasing threshold remains low even in micropillars of the smallest diameter. We show that this feature can be traced back to a sidewall roughness grain size below 3 nm and to suppressed in-plane polariton escape.

Ultra hybrid plasmonics: strong coupling of plexcitons with plasmon polaritons.

We report a ternary-coupled plasmonic system consisting of excitons of J-aggregated dye, localized surface plasmon polaritons of Ag nanoparticles, and propagating surface plasmon polaritons of continuous Ag film. J-aggregate dyes are uniformly self-assembled on colloidally synthesized Ag nanoprisms forming plexcitonic nanoparticles, which are placed at a distance nanometers away from the Ag thin film. The reflection measurements, corroborated by theoretical predictions, reveal that the strong coupling of plasmon polaritons and plexcitons results in a newly formed plasmon-exciton-plasmon hybridized state that we call here, reportedly for the first time, a plexcimon state. The hybrid plasmonic system shows dispersion characteristics similar to a coupled resonator optical waveguide. The group velocity of the plexcimon state approaches zero at the band edges. The ultrahybrid plasmonic system presented here is promising for a variety of light-matter interaction studies, including polariton lasers, plasmonic devices, plasmonic waveguiding, and spectroscopy.

Small-signal modulation characteristics of a polariton laser

Use of large bandgap materials together with electrical injection makes the polariton laser an attractive low-power coherent light source for medical and biomedical applications or short distance plastic fiber communication at short wavelengths (violet and ultra-violet), where a conventional laser is difficult to realize. The dynamic properties of a polariton laser have not been investigated experimentally. We have measured, for the first time, the small signal modulation characteristics of a GaN-based electrically pumped polariton laser operating at room temperature. A maximum −3 dB modulation bandwidth of 1.18 GHz is measured. The experimental results have been analyzed with a theoretical model based on the Boltzmann kinetic equations and the agreement is very good. We have also investigated frequency chirping during such modulation. Gain compression phenomenon in a polariton laser is interpreted and a value is obtained for the gain compression factor.

Exciton-photon correlations in bosonic condensates of exciton-polaritons.

Exciton-polaritons are mixed light-matter quasiparticles. We have developed a statistical model describing stochastic exciton-photon transitions within a condensate of exciton polaritons. We show that the exciton-photon correlator depends on the rate of incoherent exciton-photon transformations in the condensate. We discuss implications of this effect for the quantum statistics of photons emitted by polariton lasers.

Control of Lasing from Bloch States in Microcavity Photonic Wires via Selective Excitation and Gain

Polariton lasers, which provide low-threshold lasing, are sought as energy-efficient light sources for photonic devices. The authors create deep photonic wires in organic microcavities, altering their angle-dependent emission to facilitate polariton dispersions with coexisting localized and extended states. Selective excitation precisely controls the build-up of coherent modes, providing tunable lasing on the microscale. These experiments are performed at room temperature under ambient conditions, and thus are clearly adaptable to real-world applications.

Stochastic pumping of a polariton fluid

We investigate the response of a polariton laser driven slightly off-resonantly using light fields differing from the routinely studied coherent pump sources. The response to driving light fields with thermal and displaced thermal statistics with varying correlation times shows significant differences in the transmitted intensity, its noise, and the position of the nonlinear threshold. We predict that adding more photons on average may actually reduce the transmission through the polariton system.

Cascaded stimulated polariton scattering in a Mg:LiNbO(3) terahertz laser.

Cascaded Stimulated Polariton Scattering (SPS) to the fourth-Stokes order is observed experimentally in an intracavity THz polariton laser utilising Mg:LiNbO(3). The performance of the cascaded laser is presented, the origin of the cascaded fields is explained and compared to theory, and the potential consequences for using cascading to enhance the THz output from this type of device are discussed.

Polariton Boxes in a Tunable Fiber Cavity

Cavity polaritons are elementary half-matter, half-light excitations trapped within a microcavity that exhibit unique properties useful both for probing fundamental physics and for producing novel applications. The authors present an all-optical confinement method for tuning the energy and lifetime of cavity polaritons based on a Fabry-Perot fiber cavity plus (In,Ga)As quantum wells. This system should enable not only the study of physical phenomena, such as polariton lasing and strongly correlated behavior, but also applications in optoelectronics and quantum photonics.

Optical Tamm state and related lasing effect enhanced by planar plasmonic metamaterials

Optical Tamm state (OTS) refers to a kind of interface state between the metal layer and the photonic crystal (PC) reflectors. Given the matching conditions being satisfied, the electromagnetic waves tend to tunnel through the metal-PC hetero-structure efficiently. Quite different from the conventional surface plasmon polaritons (SPPs) on metal surface, OTSs can be excited directly by normally incident propagating waves for both TE and TM polarizations to occur. In the meantime, strong electromagnetic (EM) localization around the interface can be achieved, leading to potential applications such as polariton lasers, enhancement of Faraday rotation, various nonlinear effects, and so on.#br#To further enhance the EM localization around the interface, some well designed artificial structures are patterned on the thin metal layer. For instance, confined Tamm plasmon modes with the aid of metallic microdisks are proposed by Gazzano et al. to control the spontaneous optical emission. Moreover, in 2013 it was also demonstrated that planar plasmonic metamaterials (PPM) with electromagnetically-induced-reflection-like (EIR-like) dispersion can boost the Q-factor of OTS tunneling mode, as well as the EM localization around the interface between planar plasmonic metamaterials and PC. Both these methods can be understood in the same scheme:the structure-induced dispersion provides exotic power of modulating the propagation of OTS.#br#In this paper, the enhancement of optical Tamm state and related lasing effect is investigated by introducing planar plasmonic metamaterials with EIR-like dispersion. The planar plasmonic metamaterials are achieved by periodic patterning some plasmonic units on the planar metal layer. Through fine tuning each unit cell, EIR-like dispersion can be achieved, making the properties of hetero-structure more tunable. One-dimensional photonic crystals composed of TiO2/SiO2 are also designed properly to support the optical Tamm state in PPM-PC hetero-structure. First, to analyze the possibility of enhancing local electromagnetic field density of optical Tamm state, a transfer matrix method is performed when EIR-like dispersion of PPM structure is hired. Next, full wave simulations based on FDTD method are also carried out to verify a hetero-structure composed of PPM and one-dimensional photonic crystal embbed with gain media. By introducing gain medium into (or near) the PPM structure, where the maximum local electromagnetic field density exists, the lasing effect is found obviously enhanced. Better emitting efficiency and monochromic response can be observed compared to the common metal-PC hetero-structure. These features make our structure promising to reduce the lasing threshold, enhance the fluorescence, and so on.

Quanto-Optical Effects of Exciton-Polariton System

The mutual quantum and optical effects of exciton bound states in exciton-polartiton system in the inhomogeneous multi-layer environment in semiconductor quantum dots (SQDs) are presented. We theoretically show that how optical effects (polarization) of exciton-polariton system can affect on quantum characteristics (spin projections) which results in beats between right- and left-circularly polarized photoluminescence. Optical polarization effects in exciton-polariton interactions in SQDs enable complete studies of the exciton-polariton spin dynamics. The theoretical information on the exotic-polariton states and definition of Hamiltonian interactions according to the basis investigation of the asymptotically bihaviour of the loop function of scalar particles (electron-hole) in SQDs are determined. Using oscillator representation method, spin Hamiltonian coefficient of excitons with effective confinement potential, Coulomb and spin effects are determined. In addition we can say that controlling and understanding of spin interaction between electron- holes localized in SQDs can controlled optically effects and interactions. Spin quantum manipulations can be useful in new generation of optic-photonic studies, especially super quantum computers, Bose condensates of exciton-polariton, polariton lasers and etc

Ultrafast dynamics of nanoplasmonic stopped-light lasing.

We study the spatio-temporal dynamics of coherent amplification and lasing in planar gain-enhanced nanoplasmonic structures and show that a singularity in the density of optical states leads to a stopped-light feedback mechanism that allows for cavity-free photonic and surface-plasmon polariton nanolasing. We reveal that in the absence of cavity-induced feedback a phase-locked superposition of a quasi dispersion-free waveguide mode promotes the dynamic formation of a subwavelength lasing mode. Simulations on the basis of a full-time domain Maxwell-Bloch Langevin approach uncover a high spontaneous emission factor β≈0.9 and demonstrate that the stopped-light lasing/spasing mechanism is remarkably robust against interface roughness. Stopped-light surface-plasmon polariton lasing is shown to be stable for gain sections of a width of down to 200 nm but in wider gain structures of the order of 1 μm the dynamics is characterised by spatio-temporally oscillating lasing surface-plasmon polaritons with typical temporal and spatial periods of smaller than 5 fs and smaller than 100 nm. Stopped-light lasing thus provides opportunities for ultrafast nanolasing and the realization of ultra-thin lasing surfaces and offers a new route to ultrafast spasing and cavity-free active quantum plasmonics.

Low-Threshold near-Infrared GaAs–AlGaAs Core–Shell Nanowire Plasmon Laser

We demonstrate plasmonic lasing from metal–organic chemical vapor deposition (MOCVD)-grown GaAs–AlGaAs core–shell nanowires (NWs) with subdiffraction limit diameters of ∼150 nm placed directly on a silver thin film. The absence of a low-index dielectric spacer layer between the NW and the metal layer allows for surface plasmon polariton (SPP) lasing using a nonhybridized plasmonic mode. Unlike previously reported plasmonic NW lasers using the fundamental SPP mode, we demonstrate for the first time plasmonic NW lasing under pulsed optical excitation by using the higher order SPP mode. The higher order mode allows us to alleviate the high losses associated with the fundamental plasmonic mode. We observed lasing at temperatures up to 125 K. Our demonstration of a plasmonic laser based on GaAs emitting in the near-infrared region will be useful for the on-chip integration of nanophotonic and electronic devices and the development of GaAs-based plasmonic devices.

Electro-optical switching between polariton and cavity lasing in an InGaAs quantum well microcavity.

We report on the condensation of microcavity exciton polaritons under optical excitation in a microcavity with four embedded InGaAs quantum wells. The polariton laser is characterized by a distinct non-linearity in the input-output-characteristics, which is accompanied by a drop of the emission linewidth indicating temporal coherence and a characteristic persisting emission blueshift with increased particle density. The temporal coherence of the device at threshold is underlined by a characteristic drop of the second order coherence function to a value close to 1. Furthermore an external electric field is used to switch between polariton regime, polariton condensate and photon lasing.

Terahertz emission from multiple-microcavity exciton-polariton lasers

Terahertz emission between exciton-polariton branches in semiconductor microcavities is expected to be strongly stimulated in the polariton laser regime due to the high density of particles in the lower state (final-state stimulation effect). However, nonradiative scattering processes depopulate the upper state and greatly hinder the efficiency of such terahertz sources. In this work, we suggest a scheme using multiple microcavities and exploiting the transition between two interband polariton branches located below the exciton level. We compare the nonradiative processes loss rates in single and double cavity devices and we show that a dramatic reduction can be achieved in the latter, enhancing the efficiency of the terahertz emission.

Exciton–polariton condensates

Recently a new type of system exhibiting spontaneous coherence has emerged—the exciton–polariton condensate. Exciton–polaritons (or polaritons for short) are bosonic quasiparticles that exist inside semiconductor microcavities, consisting of a superposition of an exciton and a cavity photon. Above a threshold density the polaritons macroscopically occupy the same quantum state, forming a condensate. The polaritons have a lifetime that is typically comparable to or shorter than thermalization times, giving them an inherently non-equilibrium nature. Nevertheless, they exhibit many of the features that would be expected of equilibrium Bose–Einstein condensates (BECs). The non-equilibrium nature of the system raises fundamental questions as to what it means for a system to be a BEC, and introduces new physics beyond that seen in other macroscopically coherent systems. In this review we focus on several physical phenomena exhibited by exciton–polariton condensates. In particular, we examine topics such as the difference between a polariton BEC, a polariton laser and a photon laser, as well as physical phenomena such as superfluidity, vortex formation, and Berezinskii–Kosterlitz–Thouless and Bardeen–Cooper–Schrieffer physics. We also discuss the physics and applications of engineered polariton structures.

Biexcitonic molecules survive excitons at the Mott transition.

When the carrier density is increased in a semiconductor, according to the predictions of Sir Nevil Mott, a transition should occur from an insulating state consisting of a gas of excitons to a conductive electron-hole plasma. This crossover, usually referred to as the Mott transition, is driven by the mutual effects of phase-space filling and Coulomb screening because of the presence of other charges nearby. It drastically affects the optical and electrical characteristics of semiconductors and may, for example, drive the transition from a polariton laser to a vertical cavity surface-emitting laser. Usually, the possible existence of excitonic molecules (or biexcitons) is neglected in the understanding of the Mott transition because the biexciton is supposed to be less robust against screening effects. Here, against common beliefs, we observe that the biexciton in a GaN quantum well is more stable towards the Mott transition than the exciton.

A room temperature low-threshold ultraviolet plasmonic nanolaser

Constrained by large ohmic and radiation losses, plasmonic nanolasers operated at visible regime are usually achieved either with a high threshold (10(2)-10(4) MW cm(-2)) or at cryogenic temperatures (4-120 K). Particularly, the bending-back effect of surface plasmon (SP) dispersion at high energy makes the SP lasing below 450 nm more challenging. Here we demonstrate the first strong room temperature ultraviolet (~370 nm) SP polariton laser with an extremely low threshold (~3.5 MW cm(-2)). We find that a closed-contact planar semiconductor-insulator-metal interface greatly lessens the scattering loss, and more importantly, efficiently promotes the exciton-SP energy transfer thus furnishes adequate optical gain to compensate the loss. An excitation polarization-dependent lasing action is observed and interpreted with a microscopic energy-transfer process from excitons to SPs. Our work advances the fundamental understanding of hybrid plasmonic waveguide laser and provides a solution of realizing room temperature UV nanolasers for biological applications and information technologies.

Erratum: Generic picture of the emission properties of III-nitride polariton laser diodes: Steady state and current modulation response [Phys. Rev. B86, 125308 (2012)

Erratum: Generic picture of the emission properties of III-nitride polariton laser diodes: Steady state and current modulation response [Phys. Rev. B<b>86</b>, 125308 (2012)

The practical polariton laser [News

Lasers have largely replaced the copper wiring of old to speedily stream bits among servers in large data centers. Engineers have long dreamed that they could use lasers to do the same within the servers‚ data-congested processors, too. One problem standing in their way is that even the most efficient lasers need an awful lot of current before they light up. But a new kind of device, the polariton laser, could light the way using merely a trickle of electrons. Until recently, however, the device has worked only in an impractical environment.

A practical polariton laser

The report of an electrically pumped polariton laser that operates at room temperature and relies on an inversionless lasing scheme holds promise for realizing a new breed of very low threshold semiconductor lasers.