Suchergebnisse

Publisher's version (útgefin grein) ; Highly nonlinear optical materials with strong effective photon-photon interactions are required for ultrafast and quantum optical signal processing circuitry. Here we report strong Kerr-like nonlinearities by employing efficient optical transitions of charged excitons (trions) observed in semiconducting transition metal dichalcogenides (TMDCs). By hybridising trions in monolayer MoSe2 at low electron densities with a microcavity mode, we realise trion-polaritons exhibiting significant energy shifts at small photon fluxes due to phase space filling. We find the ratio of trion- to neutral exciton–polariton interaction strength is in the range from 10 to 100 in TMDC materials and that trion-polariton nonlinearity is comparable to that in other polariton systems. The results are in good agreement with a theory accounting for the composite nature of excitons and trions and deviation of their statistics from that of ideal bosons and fermions. Our findings open a way to scalable quantum optics applications with TMDCs. ; The authors acknowledge the support from the UK EPSRC grants EP/N031776/1, EP/M012727/1, EP/P026850/1 and from the mega-grant No. 14.Y26.31.0015 of the Ministry of Education and Science of the Russian Federation. O.K. thanks to ITMO Fellowship and Professorship Program. V.S. and I.A.S. acknowledge support from goszadanie no 3.2614.2017/4.6 of the Ministry of Education and Science of the Russian Federation and Icelandic research fund, grant No. 163082-051. A.C. and A.I.T. thank the financial support of the European Union's Horizon 2020 research and innovation programme under ITN Spin-NANO Marie Sklodowska-Curie grant agreement no. 676108. ; Peer Reviewed

We explore phase transitions of polariton wave packets, first, to a soliton and then to a standing wave polariton condensate in a multimode microwire system, mediated by nonlinear polariton interactions. At low excitation density, we observe ballistic propagation of the multimode polariton wave packets arising from the interference between different transverse modes. With increasing excitation density, the wave packets transform into single-mode bright solitons due to effects of both intermodal and intramodal polariton-polariton scattering. Further increase of the excitation density increases thermalization speed, leading to relaxation of the polariton density from a solitonic spectrum distribution in momentum space down to low momenta, with the resultant formation of a nonequilibrium condensate manifested by a standing wave pattern across the whole sample. ; M. S. and D. N. K. acknowledge support from the Leverhulme Trust Grant No. RPG-2013-339. M. S., J. K. C., P. M. W., B. R., M. S. S., and D. N. K. acknowledge the support from the EPSRC Grants No. EP/J007544/1 and No. EP/N031776/1 and the ERC Advanced Grant EXCIPOL 320570. D. V. S. acknowledges the Russian Foundation for Basic Research (16-52-150006) and the ITMO University Fellowship through the Government of Russia Grant No. 074-U01. H. S. and I. A. S. acknowledge the support by the Research Fund of the University of Iceland, The Icelandic Research Fund, Grant No. 163082-051 and the Project 3.2614.2017/4.6 of the Ministry of Education and Science of Russian Federation. I. A. S., M. S. S., and D. N. K. Megagrant No. 14.Y26.31.0015 of the Ministry of Education and Science of Russian Federation. We thank Marzena Szymańska for helpful discussions. ; Peer Reviewed

It is demonstrated that the emission of InAs quantum dots (QDs) capped with GaAsSb can be extended from 1.28 to 1.6 µm by increasing the Sb composition of the capping layer from 14% to 26%. Photoluminescence excitation spectroscopy is applied to investigate the nature of this large redshift. The dominant mechanism is shown to be the formation of a type-II transition between an electron state in the InAs QDs and a hole state in the GaAsSb capping layer. The prospects for using these structures to fabricate 1.55 µm injection lasers are discussed. ; This work is supported by the U.K. Engineering and Physical Sciences Research Council (EPSRC) (Grant No.GR/S49308/01) and the European Union Network of Excellence "SANDiE" (Contract No. 500101). ; Peer reviewed

Publisher's version (útgefin grein). ; Strain engineering is a powerful tool for tuning physical properties of 2D materials, including monolayer transition metal dichalcogenides (TMDs)—direct bandgap semiconductors with strong excitonic response. Deformation of TMD monolayers allows inducing modulation of exciton potential and, ultimately, creating single-photon emitters at desired positions. The performance of such systems is critically dependent on the exciton energy profile and maximum possible exciton energy shift that can be achieved under local impact until the monolayer rupture. Here, we study the evolution of two-dimensional exciton energy profile induced in a MoSe2 monolayer under incremental local indentation until the rupture. We controllably stress the flake with an atomic force microscope tip and perform in situ spatiospectral mapping of the excitonic photoluminescence in the vicinity of the indentation point. In order to accurately fit the experimental data, we combine numerical simulations with a simple model of strain-induced modification of the local excitonic response and carefully account for the optical resolution of the setup. This allows us to extract deformation, strain, and exciton energy profiles obtained at each indentation depth. The maximum exciton energy shift induced by local deformation achieved at 300 nm indentation reaches the value of 36.5 meV and corresponds to 1.15% strain of the monolayer. Our approach is a powerful tool for in situ characterization of local optomechanical properties of 2D direct bandgap semiconductors with strong excitonic response. ; The authors acknowledge funding from the Ministry of Education and Science of the Russian Federation (Megagrant No. 14.Y26.31.0015, Zadanie No. 3.8891.2017/8.9, and Zadanie No. 3.1365.2017/4.6). I. V. Iorsh acknowledges the support of Grant of President of Russian Federation No. MK-6248.2018.2. A.I.T. and D.N.K. acknowledge UK EPSRC Grant No. EP/P026850/1. V.K. acknowledges support from the Government of the Russian Federation through the ITMO Fellowship and Professorship Program. ; Peer Reviewed