Imperial College London

ProfessorRupertOulton

Faculty of Natural SciencesDepartment of Physics

Professor of Nanophotonics
 
 
 
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Contact

 

+44 (0)20 7594 7576r.oulton

 
 
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Location

 

914Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

151 results found

Pearce E, Phillips CC, Oulton RF, Clark ASet al., 2020, Heralded spectroscopy with a fiber photon-pair source, APPLIED PHYSICS LETTERS, Vol: 117, ISSN: 0003-6951

Journal article

Grinblat G, Zhang H, Nielsen MP, Krivitsky L, Berte R, Li Y, Tilmann B, Cortes E, Oulton RF, Kuznetsov A, Maier SAet al., 2020, Efficient ultrafast all-optical modulation in a nonlinear crystalline gallium phosphide nanodisk at the anapole excitation, SCIENCE ADVANCES, Vol: 6, ISSN: 2375-2548

Journal article

Sistani M, Bartmann MG, Gusken NA, Oulton RF, Keshmiri H, Minh AL, Momtaz ZS, Den Hertog M, Lugstein Aet al., 2020, Plasmon-Driven Hot Electron Transfer at Atomically Sharp Metal-Semiconductor Nanojunctions, ACS PHOTONICS, Vol: 7, Pages: 1642-1648, ISSN: 2330-4022

Journal article

Sistani M, Bartmann MG, Gusken NA, Oulton RF, Keshmiri H, Minh AL, Robin E, den Hertog M, Lugstein Aet al., 2020, Stimulated Raman Scattering in Ge Nanowires, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 124, Pages: 13872-13877, ISSN: 1932-7447

Journal article

Azzam S, Kildishev A, Ma R-M, Ning C-Z, Oulton R, Shalaev VM, Stockman M, Xu J-L, Zhang Xet al., 2020, Ten years of spasers and plasmonic nanolasers, LIGHT-SCIENCE & APPLICATIONS, Vol: 9, ISSN: 2047-7538

Journal article

Marques Rodrigues J, Walker BT, Dhar HS, Oulton R, Mintert F, Nyman RAet al., 2020, Non-stationary statistics and formation jitter in transient photon condensation, Nature Communications, Vol: 11, ISSN: 2041-1723

While equilibrium phase transitions are easily described by order parameters and free-energylandscapes, for their non-stationary counterparts these quantities are usually ill-defined. Here,we probe transient non-equilibrium dynamics of an optically pumped, dye-filled microcavity. Wequench the system to a far-from-equilibrium state and find delayed condensation close to a criticalexcitation energy, a transient equivalent of critical slowing down. Besides number fluctuations nearthe critical excitation energy, we show that transient phase transitions exhibit timing jitter in thecondensate formation. This jitter is a manifestation of the randomness associated with spontaneousemission, showing that condensation is a stochastic, rather than deterministic process. Despite thenon-equilibrium character of this phase transition, we construct an effective free-energy landscapethat describes the formation jitter and allows, in principle, its generalization to a wider class ofprocesses.

Journal article

Walker BT, Rodrigues JD, Dhar HS, Oulton RF, Mintert F, Nyman RAet al., 2020, Non-stationary statistics and formation jitter in transient photon condensation, Publisher: NATURE PUBLISHING GROUP

Working paper

Gusken NA, Lauri A, Li Y, Jacassi A, Matsui T, Doiron B, Bower R, Regoutz A, Mihai A, Petrov PK, Oulton RF, Cohen LF, Maier SAet al., 2020, IR hot carrier based photodetection in titanium nitride oxide thin film-Si junctions, MRS ADVANCES, Vol: 5, Pages: 1843-1850, ISSN: 2059-8521

Journal article

Sistani M, Bartmann MG, Gusken NA, Oulton RF, Keshmiri H, Seifner MS, Barth S, Fukata N, Luong MA, den Hertog MI, Lugstein Aet al., 2019, Nanoscale aluminum plasmonic waveguide with monolithically integrated germanium detector, Applied Physics Letters, Vol: 115, Pages: 161107-1-161107-4, ISSN: 0003-6951

Surface plasmon polaritons have rapidly established themselves as a promising concept for molecular sensing, near-field nanoimaging, andtransmission lines for emerging integrated ultracompact photonic circuits. In this letter, we demonstrate a highly compact surface plasmonpolariton detector based on an axial metal-semiconductor-metal nanowire heterostructure device. Here, an in-coupled surface plasmonpolariton propagates along an aluminum nanowire waveguide joined to a high index germanium segment, which effectively acts as a photoconductor at low bias. Based on this system, we experimentally verify surface plasmon propagation along monocrystalline Al nanowires asthin as 40 nm in diameters. Furthermore, the monolithic integration of plasmon generation, guiding, and detection enables us to examine thebending losses of kinked waveguides. These systematic investigations of ultrathin monocrystalline Al nanowires represent a general platformfor the evaluation of nanoscale metal based waveguides for transmission lines of next generation high-speed ultracompact on-chip photoniccircuits.

Journal article

Dichtl P, Gennaro SD, Li Y, Maier SA, Oulton RFet al., 2019, Exploiting the nonlinear optical response of gold nanoantennas for ultrafast pulse characterisation

© OSA 2019. The Author(s). Two femtosecond laser pulses in the near-infrared and near the edge of the visible waveband are characterized simultaneously by a time-resolved analysis of nonlinear scattering from gold nanoparticles.

Conference paper

Dichtl P, Abdelwahab I, Grinblat G, Leng K, Chi X, Park IH, Nielsen MP, Oulton RF, Loh KP, Maier SAet al., 2019, Giant and tunable optical nonlinearity in single-crystalline 2D perovskites due to excitonic and plasma effects

© OSA 2019. The Author(s). 2D Ruddlesden-Popper-type lead halide perovskites exhibit a strong third-order nonlinear response around excitonic resonance, which is characterized with Z-scan measurements. We find large absolute values and a sign change of both nonlinear refraction and absorption.

Conference paper

Gennaro SD, Li Y, Maier SA, Oulton RFet al., 2019, Nonlinear Pancharatnam-Berry Phase Metasurfaces beyond the Dipole Approximation, ACS PHOTONICS, Vol: 6, Pages: 2335-2341, ISSN: 2330-4022

Journal article

Grandi S, Nielsen MP, Cambiasso J, Boissier S, Major K, Reardon C, Krauss TF, Oulton R, Hinds E, Clark Aet al., 2019, Hybrid plasmonic waveguide coupling of photons from a single molecule, APL Photonics, Vol: 4, Pages: 086101-1-086101-6, ISSN: 2378-0967

We demonstrate the emission of photons from a single molecule into a hybrid gap plasmon waveguide (HGPW). Crystals of anthracene, doped with dibenzoterrylene (DBT), are grown on top of the waveguides. We investigate a single DBT molecule coupled to the plasmonic region of one of the guides, and determine its in-plane orientation, excited state lifetime and saturation intensity. The molecule emits light into the guide, which is remotely out-coupled by a grating. The second-order autocorrelation and cross-correlation functions show that the emitter is a single molecule and that the light emerging from the grating comes from that molecule. The couplinge fficiency is found to be βWG = 11.6(1:5)%. This type of structure is promising for building new functionality into quantum-photonic circuits, where localised regions of strong emitter-guide coupling can be interconnected by low-loss dielectric guides.

Journal article

Grinblat G, Abdelwahab I, Nielsen MP, Dichtl P, Leng K, Oulton RF, Loh KP, Maier SAet al., 2019, Ultrafast All-Optical Modulation in 2D Hybrid Perovskites, ACS NANO, Vol: 13, Pages: 9504-9510, ISSN: 1936-0851

Journal article

Doiron B, Li Y, Mihai A, Bower R, Alford NM, Petrov PK, Maier SA, Oulton RFet al., 2019, Plasmon-enhanced electron harvesting in robust titanium nitride nanostructures, The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces, Vol: 123, Pages: 18521-18527, ISSN: 1932-7447

Titanium nitride (TiN) continues to prove itself as an inexpensive, robust, and efficient alternative to gold in plasmonic applications. Notably, TiN has improved hot electron-harvesting and photocatalytic abilities compared to gold systems, which we recently attributed to the role of oxygen in TiN and its native semiconducting TiO2–x surface layer. Here, we explore the role of localized surface plasmon resonances (LSPRs) on electron harvesting across the TiN/TiO2–x interface and probe the resilience of TiN nanostructures under high-power laser illumination. To investigate this, we fabricate TiN strips, in which the lateral confinement allows for the polarization-selective excitation of the LSPR. Using ultrafast pump–probe spectroscopy, optical characterization, and Raman vibrational spectroscopy, we relate the differences and changes observed in the electron behavior to specific material properties. We observe plasmon-enhanced electron harvesting beyond what is expected resulting from the enhanced absorption of the plasmonic mode. We accredit this to the surface oxide damping the plasmon resonance, providing additional nonradiative loss channels. Subsequently, we show that low-power annealing of the surface oxide layer reduces the trap density at the interface and increases the initial harvested electron concentration. The unique properties of TiN make it important in the future development of plasmonic electron-harvesting applications.

Journal article

Abdelwahab I, Dichtl P, Grinblat G, Leng K, Chi X, Park I-H, Nielsen MP, Oulton RF, Loh KP, Maier SAet al., 2019, Giant and Tunable Optical Nonlinearity in Single-Crystalline 2D Perovskites due to Excitonic and Plasma Effects, ADVANCED MATERIALS, Vol: 31, ISSN: 0935-9648

Journal article

Shautsova V, Gusken NA, Sidiropoulos T, Xiao X, Black NCG, Gilbertson AM, Giannini V, Maier SA, Cohen LF, Oulton RFet al., 2019, Plasmonic photo-thermo-electric effect in graphene, Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-8989

We present a novel photo-thermo-electric effect in graphene photo-detectors established by hot electrons concentration gradients at plasmonic contacts. Our description is crucial for an in depth understanding of graphene-based photo detection devices.

Conference paper

Grinblat G, Nielsen M, Dichtl P, Li Y, Oulton R, Maier Set al., 2019, Ultrafast sub-30 FS all-optical switching based on gallium phosphide, Science Advances, Vol: 5, ISSN: 2375-2548

Gallium Phosphide (GaP) is one of the few available materials with strong optical nonlinearity and negligible losses in the visible ( >450 )and near-infrared regime. In this work, we demonstrate that a GaP film can generate sub-30 fs (full width at half maximum) transmission modulation of up to ⁓70% in the 600-1000 nm wavelength range. Nonlinear simulations using parameters measured by the Z-scan approach indicate that the transmission modulation arises from the optical Kerr effect and two-photon absorption. Due to the absence of linear absorption, no slower free-carrier contribution is detected. These findings place GaP as a promising ultrafast material for all-optical switching at modulation speeds of up to 20 THz.

Journal article

Grandi S, Nielsen MP, Cambiasso J, Boissier S, Major KD, Reardon C, Krauss TF, Oulton RF, Hinds EA, Clark ASet al., 2019, Hybrid plasmonic waveguide coupling of photons from a single molecule

We demonstrate the emission of photons from a single molecule into a hybridgap plasmon waveguide (HGPW). Crystals of anthracene, doped withdibenzoterrylene (DBT), are grown on top of the waveguides. We investigate asingle DBT molecule coupled to the plasmonic region of one of the guides, anddetermine its in-plane orientation, excited state lifetime and saturationintensity. The molecule emits light into the guide, which is remotelyout-coupled by a grating. The second-order auto-correlation andcross-correlation functions show that the emitter is a single molecule and thatthe light emerging from the grating comes from that molecule. The couplingefficiency is found to be $\beta_{WG}=11.6(1.5)\%$. This type of structure ispromising for building new functionality into quantum-photonic circuits, wherelocalised regions of strong emitter-guide coupling can be interconnected bylow-loss dielectric guides.

Working paper

Gusken NA, Nielsen MP, Nguyen NB, Shi X, Dichtl P, Maier SA, Oulton RFet al., 2019, Efficient four wave mixing and low-loss in-coupling in hybrid gap plasmonic waveguides

© 2019 The Author(s) 2019 OSA. We show efficient four-wave-mixing over μm length-scales with a signal-to-idler conversion efficiency of 1% enabled by strong nonlinearities and highly confined fields. Furthermore, we demonstrate low-loss in-coupling into nanometer gaps with an efficiency of 80%.

Conference paper

Aizpurua J, Ashfold M, Baletto F, Baumberg J, Christopher P, Cortés E, de Nijs B, Diaz Fernandez Y, Gargiulo J, Gawinkowski S, Halas N, Hamans R, Jankiewicz B, Khurgin J, Kumar PV, Liu J, Maier S, Maurer RJ, Mount A, Mueller NS, Oulton R, Parente M, Park JY, Polanyi J, Quiroz J, Rejman S, Schlücker S, Schultz Z, Sivan Y, Tagliabue G, Thangamuthu M, Torrente-Murciano L, Xiao X, Zayats A, Zhan Cet al., 2019, Dynamics of hot electron generation in metallic nanostructures: general discussion., Faraday Discuss, Vol: 214, Pages: 123-146

Journal article

Gusken NA, Lauri A, Li Y, Matsui T, Doiron B, Bower R, Regoutz A, Mihai A, Petrov PK, Oulton RF, Cohen LF, Maier SAet al., 2019, TiO2-x-enhanced IR hot carrier based photodetection in metal thin film-si junctions, ACS Photonics, Vol: 6, Pages: 953-960, ISSN: 2330-4022

We investigate titanium nitride (TiN) thin film coatings on silicon for CMOS-compatible sub-bandgap charge separation upon incident illumination, which is a key feature in the vast field of on-chip photodetection and related integrated photonic devices. Titanium nitride of tunable oxidation distributions serves as an adjustable broadband light absorber with high mechanical robustness and strong chemical resistivity. Backside-illuminated TiN on p-type Si (pSi) constitutes a self-powered and refractory alternative for photodetection, providing a photoresponsivity of about ∼1 mA/W at 1250 nm and zero bias while outperforming conventional metal coatings such as gold (Au). Our study discloses that the enhanced photoresponse of TiN/pSi in the near-infrared spectral range is directly linked to trap states in an ultrathin TiO2–x interfacial interlayer that forms between TiN and Si. We show that a pSi substrate in conjunction with a few nanometer thick amorphous TiO2–x film can serve as a platform for photocurrent enhancement of various other metals such as Au and Ti. Moreover, the photoresponse of Au on a TiO2–x/pSi platform can be increased to about 4 mA/W under 0.45 V reverse bias at 1250 nm, allowing for controlled photoswitching. A clear deviation from the typically assumed Fowler-like response is observed, and an alternative mechanism is proposed to account for the metal/semiconductor TiO2–x interlayer, capable of facilitating hole transport.

Journal article

Doiron B, Mota M, Wells MP, Bower R, Mihai A, Li Y, Cohen LF, Alford NM, Petrov PK, Oulton RF, Maier SAet al., 2019, Quantifying figures of merit for localized surface plasmon resonance applications: a materials survey, ACS Photonics, Vol: 6, Pages: 240-259, ISSN: 2330-4022

Using localized surface plasmon resonances (LSPR) to focus electromagnetic radiation to the nanoscale shows the promise of unprecedented capabilities in optoelectronic devices, medical treatments and nanoscale chemistry, due to a strong enhancement of light-matter interactions. As we continue to explore novel applications, we require a systematic quantitative method to compare suitability across different geometries and a growing library of materials. In this work, we propose application-specific figures of merit constructed from fundamental electronic and optical properties of each material. We compare 17 materials from four material classes (noble metals, refractory metals, transition metal nitrides, and conductive oxides) considering eight topical LSPR applications. Our figures of merit go beyond purely electromagnetic effects and account for the materials’ thermal properties, interactions with adjacent materials, and realistic illumination conditions. For each application we compare, for simplicity, an optimized spherical antenna geometry and benchmark our proposed choice against the state-of-the-art from the literature. Our propositions suggest the most suitable plasmonic materials for key technology applications and can act as a starting point for those working directly on the design, fabrication, and testing of such devices.

Journal article

Dichtl P, Abdelwahab I, Grinblat G, Leng K, Chi X, Park IH, Nielsen MP, Oulton RF, Loh KP, Maier SAet al., 2019, Giant and tunable optical nonlinearity in single-crystalline 2D perovskites due to excitonic and plasma effects

© 2019 The Author(s) 2D Ruddlesden-Popper-type lead halide perovskites exhibit a strong third-order nonlinear response around excitonic resonance, which is characterized with Z-scan measurements. We find large absolute values and a sign change of both nonlinear refraction and absorption.

Conference paper

Ma R-M, Oulton RF, 2019, Applications of nanolasers, NATURE NANOTECHNOLOGY, Vol: 14, Pages: 12-22, ISSN: 1748-3387

Journal article

Gusken NA, Nielsen MP, Nguyen NB, Shi X, Dichtl P, Maier SA, Oulton RFet al., 2019, Efficient four wave mixing and low-loss in-coupling in hybrid gap plasmonic waveguides, Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-9020

Conference paper

Grinblat G, Berte R, Nielsen MP, Li Y, Oulton RF, Maier SAet al., 2018, Sub-20 fs all-optical switching in a single Au-Clad Si nanodisk, Nano Letters, Vol: 18, Pages: 7896-7900, ISSN: 1530-6984

Dielectric nanoantennas have recently emerged as promising elements for nonlinear and ultrafast nanophotonics due to their ability to concentrate light on the nanometer scale with low losses, while exhibiting large nonlinear susceptibilities. In this work, we demonstrate that single Si nanodisks covered with a thin 30 nm thick layer of Au can generate positive and negative sub-20 fs reflectivity modulations of ∼0.3% in the vicinity of the first-order anapole mode, when excited around the second-order anapole mode. The experimental results, characterized in the visible to near-infrared spectral range, suggest that the nonlinear optical Kerr effect is the responsible mechanism for the observed all-optical switching phenomena. These findings represent an important step toward nanoscale ultrafast all-optical signal processing.

Journal article

Shautsova V, Sidiropoulos T, Xiao X, Gusken N, Black N, Gilbertson A, Maier S, Cohen L, Oulton Ret al., 2018, Plasmon induced thermoelectric effect in graphene, Nature Communications, Vol: 9, ISSN: 2041-1723

Graphene has emerged as a promising material for optoelectronics due to its potential for ultrafast and broad-band photodetection. The photoresponse of graphene junctions is characterized by two competing photocurrent generation mechanisms: a conventional photovoltaic effect and a more dominant hot-carrier-assisted photothermoelectric (PTE) effect. The PTE effect is understood to rely on variations in the Seebeck coefficient through the graphene doping profile. A second PTE effect can occur across a homogeneous graphene channel in the presence of an electronic temperature gradient. Here, we study the latter effect facilitated by strongly localised plasmonic heating of graphene carriers in the presence of nanostructured electrical contacts resulting in electronic temperatures of the order of 2000 K. At certain conditions, the plasmon-induced PTE photocurrent contribution can be isolated. In this regime, the device effectively operates as a sensitive electronic thermometer and as such represents an enabling technology for development of hot carrier based plasmonic devices.

Journal article

Gusken N, Nielsen M, Nguyen N, Maier S, Oulton Ret al., 2018, Nanofocusing in SOI-based hybrid plasmonic metal slot waveguides, Optics Express, Vol: 26, Pages: 30634-30643, ISSN: 1094-4087

Abstract: Through a process of efficient dielectric to metallic waveguide mode conversion, we calculate a >400-fold field intensity enhancement in a silicon photonics compatible nanofocusing device. A metallic slot waveguide sits on top of the silicon slab waveguide with nanofocusing being achieved by tapering the slot width gradually. We evaluate the conversion between the numerous photonic modes of the planar silicon waveguide slab and the most confined plasmonic mode of a 20 x 50 nm2 slot in the metallic film. With an efficiency of ~80%, this system enables remarkably effective nanofocusing, although the small amount of inter-mode coupling shows that this structure is not quite adiabatic. In order to couple photonic and plasmonic modes efficiently, in-plane focusing is required, simulated here by curved input grating couplers. The nanofocusing device shows how to efficiently bridge the photonic micro-regime and the plasmonic nano-regime whilst maintaining compatibility with the silicon photonics platform.

Journal article

Kumar R, Verzhbitskiy I, Giustiniano F, Sidiropoulos TPH, Oulton RF, Eda Get al., 2018, Interlayer screening effects in WS2/WSe2 van der Waals hetero-bilayer, 2D MATERIALS, Vol: 5, ISSN: 2053-1583

Journal article

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