Nature Photonics

/Nature Photonics

Control of semiconductor emitter frequency by increasing polariton momenta

2018-06-04T18:36:44+00:00 June 4th, 2018|Categories: Publications|Tags: |

Control of semiconductor emitter frequency by increasing polariton momentaControl of semiconductor emitter frequency by increasing polariton momenta, Published online: 04 June 2018; doi:10.1038/s41566-018-0176-6While modifications of emission and absorption rates are commonplace in photonics, similar manipulations of emitter transition frequencies are challenging. Here, 2D polaritons in graphene are predicted to enable non-vertical electronic transitions in a quantum well, controlling the transition frequencies by inducing an effective non-locality.

Published in: "Nature Photonics".

Gate-tunable third-order nonlinear optical response of massless Dirac fermions in graphene

2018-05-21T16:31:29+00:00 May 21st, 2018|Categories: Publications|Tags: |

Gate-tunable third-order nonlinear optical response of massless Dirac fermions in grapheneGate-tunable third-order nonlinear optical response of massless Dirac fermions in graphene, Published online: 21 May 2018; doi:10.1038/s41566-018-0175-7Third-harmonic generation and four-wave mixing of light can be enhanced in graphene with gate tuning to adjust the doping level. The findings may lead to new graphene-based nonlinear optoelectronic devices.

Published in: "Nature Photonics".

Silicon Mie resonators for highly directional light emission from monolayer MoS<sub>2</sub>

2018-04-23T16:30:04+00:00 April 23rd, 2018|Categories: Publications|Tags: |

Silicon Mie resonators for highly directional light emission from monolayer MoS2Silicon Mie resonators for highly directional light emission from monolayer MoS<sub>2</sub>, Published online: 23 April 2018; doi:10.1038/s41566-018-0155-yBased on a modified Mie scattering theory, several pathways to achieve control over the directionality, polarization state and spectral emission that rely on a coherent coupling of an emitting dipole in monolayer MoS2 to optical resonances of a silicon nanowire are reported.

Published in: "Nature Photonics".

Terahertz surprises

2018-02-26T16:30:20+00:00 February 26th, 2018|Categories: Publications|Tags: |

Terahertz surprisesTerahertz surprises, Published online: 26 February 2018; doi:10.1038/s41566-018-0115-6The observation of terahertz nonlinearities in graphene and quantum wells and the emission of terahertz waves from water show that terahertz science is still a fertile area of research that is full of surprises.

Published in: "Nature Photonics".

Telecom meets terahertz

2017-12-22T18:30:04+00:00 December 22nd, 2017|Categories: Publications|Tags: |

Telecom meets terahertzTelecom meets terahertz, Published online: 22 December 2017; doi:10.1038/s41566-017-0073-4Excitation and gate tuning of terahertz plasmons in dual-layer graphene integrated into on-chip telecom photonic waveguides using infrared lasers has now been demonstrated. This may open the door to atomically thick optoelectronic devices for security, tomography or data processing.

Published in: "Nature Photonics".

Broadband gate-tunable terahertz plasmons in graphene heterostructures

2017-12-11T18:31:14+00:00 December 11th, 2017|Categories: Publications|Tags: , |

Broadband gate-tunable terahertz plasmons in graphene heterostructuresBroadband gate-tunable terahertz plasmons in graphene heterostructures, Published online: 11 December 2017; doi:10.1038/s41566-017-0054-7An all-optical difference frequency process is exploited to generate terahertz graphene plasmons that are tunable over an octave.

Published in: "Nature Photonics".

Chalcogenide glass-on-graphene photonics

2017-10-30T16:29:19+00:00 October 30th, 2017|Categories: Publications|Tags: |

Chalcogenide glass-on-graphene photonicsNature Photonics, Published online: 30 October 2017; doi:10.1038/s41566-017-0033-zExploiting the peculiar properties of graphene, a series of high-performance glass-on-graphene devices, such as polarizers, thermo-optic switches and mid-infrared waveguide-integrated photodetectors and modulators are realized.

Published in: "Nature Photonics".

Valley-addressable polaritons in atomically thin semiconductors

2017-08-01T04:29:34+00:00 August 1st, 2017|Categories: Publications|Tags: |

Nature Photonics 11, 497 (2017). doi:10.1038/nphoton.2017.125 Authors: S. Dufferwiel, T. P. Lyons, D. D. Solnyshkov, A. A. P. Trichet, F. Withers, S. Schwarz, G. Malpuech, J. M. Smith, K. S. Novoselov, M. S. Skolnick, D. N. Krizhanovskii & A. I. Tartakovskii The locking of the electron spin to the valley degree of freedom in transition metal dichalcogenide (TMD) monolayers has seen these materials emerge as a promising platform in valleytronics. When embedded in optical microcavities, the large oscillator strengths of excitonic transitions in TMDs allow the formation of polaritons that are part-light part-matter quasiparticles. Here, we report that polaritons in MoSe2 show an efficient retention of the valley pseudospin contrasting them with excitons and trions in this material. We find that the degree of the valley pseudospin retention is dependent on the photon, exciton and trion fractions in the polariton states. This allows us to conclude that in the polaritonic regime, cavity-modified exciton relaxation inhibits loss of the valley pseudospin. The valley-addressable exciton-polaritons and trion-polaritons presented here offer robust valley-polarized states with the potential for valleytronic devices based on TMDs embedded in photonic structures and valley-dependent nonlinear polariton–polariton interactions.

Published in: "Nature Photonics".

Optical control of room-temperature valley polaritons

2017-08-01T04:29:35+00:00 August 1st, 2017|Categories: Publications|

Nature Photonics 11, 491 (2017). doi:10.1038/nphoton.2017.121 Authors: Zheng Sun, Jie Gu, Areg Ghazaryan, Zav Shotan, Christopher R. Considine, Michael Dollar, Biswanath Chakraborty, Xiaoze Liu, Pouyan Ghaemi, Stéphane Kéna-Cohen & Vinod M. Menon The formation of half-light half-matter quasiparticles under strong coupling results in properties unique from those of the constituent components. Fingerprints of both light and matter are imprinted on the new quasiparticles, called polaritons. In the context of two-dimensional (2D) materials, this opens up the possibility of exploiting the intriguing spin–valley physics of a bare semiconductor combined with the light mass of the photonic component for possible quantum technologies. Specifically, the valley degree of freedom, which remained largely unexplored until the advent of these materials, is highly attractive in this context as it provides an optically accessible route for the control and manipulation of electron spin. Here, we report the observation of room-temperature strongly coupled light–matter quasiparticles that are valley polarized because of the coupling of photons with specific helicity to excitons that occupy quantum mechanically distinct valleys in momentum space. The realization of valley polaritons in 2D semiconductor microcavities presents the first step towards engineering valley-polaritonic devices.

Published in: "Nature Photonics".

2D materials: Valley polaritons

2017-08-01T04:29:33+00:00 August 1st, 2017|Categories: Publications|

Nature Photonics 11, 455 (2017). doi:10.1038/nphoton.2017.135 Author: Gabriele Grosso Spin–valley coupling in transition metal dichalcogenides has been shown to persist at room temperature when excitons are coherently coupled to cavity photons.

Published in: "Nature Photonics".

Electrical 2π phase control of infrared light in a 350-nm footprint using graphene plasmons

2017-07-31T12:29:34+00:00 July 31st, 2017|Categories: Publications|Tags: |

Nature Photonics 11, 421 (2017). doi:10.1038/nphoton.2017.98 Authors: Achim Woessner, Yuanda Gao, Iacopo Torre, Mark B. Lundeberg, Cheng Tan, Kenji Watanabe, Takashi Taniguchi, Rainer Hillenbrand, James Hone, Marco Polini & Frank H. L. Koppens Modulating the amplitude and phase of light is at the heart of many applications such as wavefront shaping, transformation optics, phased arrays, modulators and sensors. Performing this task with high efficiency and small footprint is a formidable challenge. Metasurfaces and plasmonics are promising, but metals exhibit weak electro-optic effects. Two-dimensional materials, such as graphene, have shown great performance as modulators with small drive voltages. Here, we show a graphene plasmonic phase modulator that is capable of tuning the phase between 0 and 2π in situ. The device length of 350 nm is more than 30 times shorter than the 10.6 μm free-space wavelength. The modulation is achieved by spatially controlling the plasmon phase velocity in a device where the spatial carrier density profile is tunable. We provide a scattering theory for plasmons propagating through spatial density profiles. This work constitutes a first step towards two-dimensional transformation optics for ultracompact modulators and biosensing.

Published in: "Nature Photonics".

Valley-addressable polaritons in atomically thin semiconductors

2017-07-24T16:29:39+00:00 July 24th, 2017|Categories: Publications|Tags: |

Nature Photonics. doi:10.1038/nphoton.2017.125 Authors: S. Dufferwiel, T. P. Lyons, D. D. Solnyshkov, A. A. P. Trichet, F. Withers, S. Schwarz, G. Malpuech, J. M. Smith, K. S. Novoselov, M. S. Skolnick, D. N. Krizhanovskii & A. I. Tartakovskii The locking of the electron spin to the valley degree of freedom in transition metal dichalcogenide (TMD) monolayers has seen these materials emerge as a promising platform in valleytronics. When embedded in optical microcavities, the large oscillator strengths of excitonic transitions in TMDs allow the formation of polaritons that are part-light part-matter quasiparticles. Here, we report that polaritons in MoSe2 show an efficient retention of the valley pseudospin contrasting them with excitons and trions in this material. We find that the degree of the valley pseudospin retention is dependent on the photon, exciton and trion fractions in the polariton states. This allows us to conclude that in the polaritonic regime, cavity-modified exciton relaxation inhibits loss of the valley pseudospin. The valley-addressable exciton-polaritons and trion-polaritons presented here offer robust valley-polarized states with the potential for valleytronic devices based on TMDs embedded in photonic structures and valley-dependent nonlinear polariton–polariton interactions.

Optical control of room-temperature valley polaritons

2017-07-24T16:29:38+00:00 July 24th, 2017|Categories: Publications|

Nature Photonics. doi:10.1038/nphoton.2017.121 Authors: Zheng Sun, Jie Gu, Areg Ghazaryan, Zav Shotan, Christopher R. Considine, Michael Dollar, Biswanath Chakraborty, Xiaoze Liu, Pouyan Ghaemi, Stéphane Kéna-Cohen & Vinod M. Menon The formation of half-light half-matter quasiparticles under strong coupling results in properties unique from those of the constituent components. Fingerprints of both light and matter are imprinted on the new quasiparticles, called polaritons. In the context of two-dimensional (2D) materials, this opens up the possibility of exploiting the intriguing spin–valley physics of a bare semiconductor combined with the light mass of the photonic component for possible quantum technologies. Specifically, the valley degree of freedom, which remained largely unexplored until the advent of these materials, is highly attractive in this context as it provides an optically accessible route for the control and manipulation of electron spin. Here, we report the observation of room-temperature strongly coupled light–matter quasiparticles that are valley polarized because of the coupling of photons with specific helicity to excitons that occupy quantum mechanically distinct valleys in momentum space. The realization of valley polaritons in 2D semiconductor microcavities presents the first step towards engineering valley-polaritonic devices.

Black phosphorus: A new bandgap tuning knob

2017-06-30T04:19:32+00:00 June 30th, 2017|Categories: Publications|Tags: |

Nature Photonics 11, 407 (2017). doi:10.1038/nphoton.2017.102 Authors: Rafael Roldán & Andres Castellanos-Gomez An external ‘tuning knob’ by means of applying a transverse electric field has been experimentally demonstrated to modify the bandgap of black phosphorus, making the two-dimensional material practical for integration in functional nanodevices.

Published in: "Nature Photonics".

Electrical 2π phase control of infrared light in a 350-nm footprint using graphene plasmons

2017-06-26T15:16:04+00:00 June 26th, 2017|Categories: Publications|Tags: |

Nature Photonics. doi:10.1038/nphoton.2017.98 Authors: Achim Woessner, Yuanda Gao, Iacopo Torre, Mark B. Lundeberg, Cheng Tan, Kenji Watanabe, Takashi Taniguchi, Rainer Hillenbrand, James Hone, Marco Polini & Frank H. L. Koppens Modulating the amplitude and phase of light is at the heart of many applications such as wavefront shaping, transformation optics, phased arrays, modulators and sensors. Performing this task with high efficiency and small footprint is a formidable challenge. Metasurfaces and plasmonics are promising, but metals exhibit weak electro-optic effects. Two-dimensional materials, such as graphene, have shown great performance as modulators with small drive voltages. Here, we show a graphene plasmonic phase modulator that is capable of tuning the phase between 0 and 2π in situ. The device length of 350 nm is more than 30 times shorter than the 10.6 μm free-space wavelength. The modulation is achieved by spatially controlling the plasmon phase velocity in a device where the spatial carrier density profile is tunable. We provide a scattering theory for plasmons propagating through spatial density profiles. This work constitutes a first step towards two-dimensional transformation optics for ultracompact modulators and biosensing.

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