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Optical metasurfaces have recently emerged as the game changer in light manipulation and opened up new perspectives in many subfields of optics and photonics. Recent developments in nonlocal metasurfaces, in which the nanoscale building blocks respond to the incoming light collectively rather than as individual objects, are especially promising for enhancing and controlling the nonlinear optical phenomena. In this article, we provide a brief overview of the basic principles of nonlocal metasurfaces in the context of their nonlinear optical functionalities. We discuss the origin and the regimes of the nonlocal response, covering the aspects of multiple scattering, radiation damping, quality factor, local-field enhancement, and temporal dynamics. Some important aspects are illustrated by computational examples. We also give our personal viewpoint on the selected ideas and research directions in nonlocal and nonlinear metasurfaces, including the role of spatial symmetry in nonlocal interactions, the effects of phase and momentum matching in frequency conversion, as well as the possibilities offered by new material platforms and novel concepts, such as bound states in the continuum, parity-time symmetry, and time-variant metasurfaces. publishedVersion

openaire: EC/H2020/101025211/EU//TEBLA Plasmonic lattices of metal nanoparticles have emerged as an effective platform for strong light–matter coupling, lasing, and Bose–Einstein condensation. However, the full potential of complex unit cell structures has not been exploited. On the other hand, bound states in continuum (BICs) have attracted attention, as they provide topologically protected optical modes with diverging quality factors. Here, we show that quadrumer nanoparticle lattices enable lasing in a quasi-BIC mode with a highly out-of-plane character. By combining theory with polarization-resolved measurements of the emission, we show that the lasing mode has a topological charge. Our analysis reveals that the mode is primarily polarized out-of-plane as a result of the quadrumer structure. The quality factors of the out-of-plane BIC modes of the quadrumer array can be exceedingly high. Our results unveil the power of complex multiparticle unit cells in creating topologically protected high-Q modes in periodic nanostructures.

We present a comprehensive study of the polarization and spatial coherence properties of the lasing modes supported by a 4-fold symmetric plasmonic lattice. By modifying only, the scattering properties of the individual particles while keeping the lattice geometry constant, we are able to distinguish the scattering induced effects from the lattice geometry induced effects. Customized interferometric measurements reveal that the lasing emission undergoes a drastic change from 1D to 2D spatial coherence with increasing particle size, accompanied with dramatic changes in the far field polarization and beaming properties. By utilizing T-matrix scattering simulations, we reveal the physical mechanism governing this transition. In particular, we find that there exists increased radiative coupling in the diagonal directions at the plane of the lattice when the particle diameter is increased. Finally, we demonstrate that the x- and y-polarized (degenerate) lasing modes become phase locked with sufficiently large particles., 12 pages, 5 figures, Preprint, Submitted to New Journal of Physics

Funding Information: This work is part of the Academy of Finland Flagship Programme, Photonics Research and Innovation (PREIN), decision 321066. Financial support from Academy of Finland (project numbers 322002, 322022 and 324353), Emil Aaltonen Foundation, Jane and Aatos Erkko Foundation, Sigrid Jusélius Foundation, Magnus Ehrnrooth Foundation, Finnish Cultural Foundation (Kalle and Dagmar Välimaa Fund) and Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters is gratefully acknowledged. This work was carried out under the Academy of Finland Centers of Excellence Program (2022–2029) in Life-Inspired Hybrid Materials (LIBER), project number (346110). We acknowledge the provision of facilities and technical support by Aalto University Bioeconomy Facilities and OtaNano – Nanomicroscopy Center (Aalto-NMC) and Micronova Nanofabrication Center. Publisher Copyright: © 2022 The Royal Society of Chemistry Here, we study optically resonant substrates fabricated using the previously reported BLIN (biotemplated lithography of inorganic nanostructures) technique with single triangle and bowtie DNA origami as templates. We present the first optical characterization of BLIN-fabricated origami-shaped silver nanoparticle patterns on glass surfaces, comprising optical transmission measurements and surface-enhanced Raman spectroscopy. The formed nanoparticle patterns are examined by optical transmission measurements and used for surface enhanced Raman spectroscopy (SERS) of Rhodamine 6G (R6G) dye molecules. Polarization-resolved simulations reveal that the higher SERS enhancement observed for the bowties is primarily due to spectral overlap of the optical resonances with the Raman transitions of R6G. The results manifest the applicability of the BLIN method and substantiate its potential in parallel and high-throughput substrate manufacturing with engineered optical properties. While the results demonstrate the crucial role of the formed nanogaps for SERS, the DNA origami may enable even more complex nanopatterns for various optical applications.

Spectral and temporal correlations determine the majority of pulse properties, and a high degree of coherence is needed for minimizing the pulse length. However, there is no simple way to quantify these correlations experimentally, and nonlinear methods are often required. In this paper, we confirm an earlier proposed experiment [Koivurova, Opt. Lett. 44, 522 (2019)]0146-959210.1364/OL.44.000522 that can accurately estimate the spectral degree of coherence of arbitrary nonstationary fields. The method is entirely linear and can retrieve the quasicoherent contribution of the spectral correlation function. In particular, the method can be used to measure the overall degree of spectral coherence in a single-shot manner. We first establish the theoretical framework behind the method and experimentally test it for a bulk-generated supercontinuum. Our experimental results are in good agreement with the theory and confirm our earlier numerical findings [Halder, Photon. Res. 7, 1345 (2019)]2327-912510.1364/PRJ.7.001345. Moreover, the results yield insight into supercontinuum generation in bulk material. acceptedVersion

Metamaterials are artificial structures exhibiting properties not found in nature, such as negative refractive index [1] , [2] . Recently, metasurfaces that consist of periodically organized metal nanoparticles, and therefore exhibit collective responses known as surface lattice resonances (SLRs), have attracted considerable attention [3] . They are often associated with high quality factors (Q~100) and are subsequently associated with considerable local-field enhancements that boost the occurring light–matter interactions [4] , [5] . However, little work yet exists on active SLR-based structures, that would permit modification of their optical properties via external means and facilitate emergence of novel SLR-based applications.

Transparent and metallic oxides based on 3d and 4d metals are promising materials for plasmonics. Here, the growth window to obtain epitaxial SrNbO3 (4d1) thin films is determined and the role of substrates to achieve optimal electrical conductivity and the largest residual resistivity ratio is disclosed. Optical measurements on optimized films indicate a large transparency at the visible with a sharp edge at about 1.9 eV, which coincides with the zero-crossing of the permittivity, allowing to identify the plasma frequency ωp. Similar features are observed in SrVO3 (3d1) films. Optical losses display well pronounced maxima at the corresponding ωp. Polarization-dependent optical transmittance measurements and ellipsometric data show a dip at ωp, occurring for p- but not s-polarized light, which is a fingerprint of optical bulk plasmon excitation. Remarkably, plasmon resonance is achieved here by using oblique incidence of light rather than phase-matching arrangements, and by exploiting charge density gradients at the film surface. This observation points to new opportunities for engineering plasmons in heterostructures., Financial support from the Spanish Ministry of Science, Innovation and Universities, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (FUNFUTURE, CEX2019-000917-S) and the MAT2017-85232-R (AEI/FEDER, EU) projects, from Generalitat de Catalunya (2017 SGR 1377), and from the COST Association (Action MP1308), is acknowledged. This work was also funded by the Deutsche Forschungsgemeinschaft (DFG) under Project No. KO 4093/1-4. T.K.H. acknowledges the Academy of Finland Flagship Programme, Photonics Research and Innovation PREIN 320166 and Academy of Finland project number 322002. The work of M.M. has been done as a part of the Ph.D. program in Physics at Universitat Autònoma de Barcelona, and was financially supported by the Spanish Ministry of Science, Innovation and Universities (BES-2015-075223). The authors are extremely thankful to Raul Solanas for his skillful operation of one PLD system used in this project (at ICMAB).

Funding Information: The work was funded by the Academy of Finland (Projects 322002, 308393, 310511). The work is part of the Academy of Finland Flagship Programme, Photonics Research and Innovation (PREIN), decisions 320166 and 320165. Publisher Copyright: © 2021 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft. We study beaming properties of laser light produced by a plasmonic lattice overlaid with organic fluorescent molecules. The crossover from spontaneous emission regime to stimulated emission regime is observed in response to increasing pump fluence. This transition is accompanied by a strong reduction of beam divergence and emission linewidth due to increased degree of spatial and temporal coherence, respectively. The feedback for the lasing signal is shown to be mainly one-dimensional due to the dipolar nature of the surface lattice resonance. Consequently, the beaming properties along x and y directions are drastically different. From the measurements, we obtain the M 2 value along both principal directions of the square lattice as a function of the pump fluence. Our work provides the first detailed analysis of the beam quality in plasmonic lattice lasers and reveals the underlying physical origin of the observed strong polarization dependent asymmetry of the lasing signal.

We demonstrate, theoretically, how the insertion of an enhanced epsilon-near-zero (EENZ) mirror in a laser cavity grants exceptional control over the coherence properties of the emitted light beam. By exploiting the peculiar sensitivity to polarization of EENZ materials, we achieve superior control over the spatial coherence of the emitted laser light, which can be switched at will between nearly incoherent and fully coherent, solely by means of polarization optics. Our EENZ cavity design is expected to be an efficient, compact, reconfigurable, and easily scalable source of light for illumination and speckle contrast imaging, as well as any other application that benefits from controlled spatial coherence.

Plasmonic metasurfaces exhibiting collective responses known as surface lattice resonances (SLRs) show potential for realizing tunable and flat photonic components for wavelength-selective processes, including lasing and optical nonlinearities. However, post-fabrication tuning of SLRs remains challenging, limiting the applicability of SLR-based components. Here, we demonstrate how the properties of high quality factor SLRs are easily modified by breaking the symmetry of the nanoparticle surroundings. We break the symmetry by changing the refractive index of the overlying immersion oil simply by controlling the ambient temperature of the device. We show that already modest temperature changes of 10{\deg}C can increase the quality factor of the investigated SLR from 400 to 750. Our results demonstrate accurate and reversible modification of the properties of the SLRs, paving the way towards tunable SLR-based photonic devices. On a more general level, our results demonstrate how symmetry breaking of the surrounding dielectric environment can be utilized for efficient and potentially ultrafast modification of the SLR properties.

Nonlinear metamaterials show potential for realizing flat nonlinear optical devices but generally lack in terms of achievable conversion efficiencies. Recent work has focused on enhancing nonlinear processes by utilizing high quality factor resonances, such as collective responses known as surface lattice resonances (SLRs) taking place in periodic metal nanoparticle arrays. Here, we investigate how the dispersive nature of SLRs affects the nonlinear responses of SLR-supporting metasurfaces. Particularly, we measure second-harmonic generation from aluminum nanoparticle arrays and demonstrate that by tilting the sample along two orthogonal directions, the sample can be made multiply-resonant for several pump and second-harmonic signal wavelength combinations. Characterized metasurfaces are estimated to exhibit a second-order susceptibility value of 0.40 pm/V, demonstrating aluminum as a potential material for nonlinear metasurfaces., Comment: 7 pages, 4 figures, supplemental material

We report on reversible all-optical emission control and lasing in plasmonic nanoparticle lattices. By incorporating photochromic molecules into the liquid gain medium composed of organic fluorescent molecules, we realize all-optical control over gain and absorption, the two key parameters associated with both conventional and nanoscale lasing. We demonstrate reversible photoswitching between two distinct modes of operation: (1) spontaneous emission to the lattice mode, characterized by broad emission line width, low emission intensity, and large angular distribution; and (2) lasing action, characterized by very narrow (sub-nm) line widths due to the emergence of increased gain and temporal coherence in the system, approximately 3 orders of magnitude increase in emission intensity, and narrow 0.7° angular divergence of the beam. A rate-equation model is employed to describe the operation of the switchable plasmonic laser. Our results provide the first demonstration of optically tunable losses in plasmonic lattice lasers, which is an important milestone for the development of active plasmonics and paves the way for ultrafast all-optical switching of plasmonic nanolasers. acceptedVersion

openaire: EC/H2020/745115/EU//OPLD Bose–Einstein condensation is a remarkable manifestation of quantum statistics and macroscopic quantum coherence. Superconductivity and superfluidity have their origin in Bose–Einstein condensation. Ultracold quantum gases have provided condensates close to the original ideas of Bose and Einstein, while condensation of polaritons and magnons has introduced novel concepts of non-equilibrium condensation. Here, we demonstrate a Bose–Einstein condensate of surface plasmon polaritons in lattice modes of a metal nanoparticle array. Interaction of the nanoscale-confined surface plasmons with a room-temperature bath of dye molecules enables thermalization and condensation in picoseconds. The ultrafast thermalization and condensation dynamics are revealed by an experiment that exploits thermalization under propagation and the open-cavity character of the system. A crossover from a Bose–Einstein condensate to usual lasing is realized by tailoring the band structure. This new condensate of surface plasmon lattice excitations has promise for future technologies due to its ultrafast, room-temperature and on-chip nature.

openaire: EC/H2020/745115/EU//OPLD Nanoscale coherent light sources offer potentially ultrafast modulation speeds, which could be utilized for novel sensors and optical switches. Plasmonic periodic structures combined with organic gain materials have emerged as promising candidates for such nanolasers. Their plasmonic component provides high intensity and ultrafast nanoscale-confined electric fields, while organic gain materials offer fabrication flexibility and a low acquisition cost. Despite reports on lasing in plasmonic arrays, lasing dynamics in these structures have not been experimentally studied yet. Here we demonstrate, for the first time, an organic dye nanoparticle-array laser with more than a 100 GHz modulation bandwidth. We show that the lasing modulation speed can be tuned by the array parameters. Accelerated dynamics is observed for plasmonic lasing modes at the blue side of the dye emission.

Controlling and generating coherent light fields in the nanoscale is critical for reducing the size of photonic circuitry. There are several demonstrations of zero-, one-, two-, and three-dimensional nanolaser architectures. Here we experimentally demonstrate a one-dimensional plasmonic laser, which consists of a periodic chain of aluminum nanoparticles and organic gain media. Lasing is observed at visible wavelengths, with clear thresholds and line widths down to 0.11 nm. Lasing occurs in a dark mode that extends over the whole structure, even outside the pumped area. The single lithography step fabrication and one-dimensional character allow for easy integration of these laser sources with other plasmonic structures.

We report on lasing at visible wavelengths in arrays of ferromagnetic Ni nanodisks overlaid with an organic gain medium. We demonstrate that by placing an organic gain material within the mode volume of the plasmonic nanoparticles both the radiative and, in particular, the high ohmic losses of Ni nanodisk resonances can be compensated. Under increasing pump fluence, the systems exhibit a transition from lattice-modified spontaneous emission to lasing, the latter being characterized by highly directional and sub-nanometer line width emission. By breaking the symmetry of the array, we observe tunable multimode lasing at two wavelengths corresponding to the particle periodicity along the two principal directions of the lattice. Our results are relevant for loss-compensated magnetoplasmonic devices and topological photonics.

We study lasing at the high-symmetry points of the Brillouin zone in a honeycomb plasmonic lattice. We use symmetry arguments to define singlet and doublet modes at the $\Kp$-points of the reciprocal space. We experimentally demonstrate lasing at the $\Kp$-points \changed{that is based on plasmonic lattice modes and two-dimensional feedback}. By comparing polarization properties to \changed{$T$-matrix} simulations, we identify the lasing mode as one of the singlets with an energy minimum at the $\Kp$-point enabling feedback. Our results offer prospects for studies of topological lasing in radiatively coupled systems.

I review our recent findings on lasing / condensation in plasmonic nanoparticle lattices1-5. The system properties can be tailored with high precision, including the lasing / condensation energies, linewidths, as well as the dimensionality of the feedback. For a 2-dimensional (2-D) square lattice, we identify lasing in the bright and the dark mode of the system1. By reducing the dimensionality to 1-D we observe the dark mode lasing2. In broken symmetry 2-dimensional rectangular lattices, we observe multimode lasing3. In honeycomb lattices with hexagonal symmetry, we observe 6 beams with specific off-normal angles and polarization properties corresponding to six-fold symmetry of such a lattice4. Finally, I review our recent studies in plasmonic Bose-Einstein condensation in plasmonic lattices5.

We report on the manipulation of magnetization by femtosecond laser pulses in a periodic array of cylindrical nickel nanoparticles. By performing experiments at different wavelength, we show that the excitation of collective surface plasmon resonances triggers demagnetization in zero field or magnetic switching in a small perpendicular field. Both magnetic effects are explained by plasmon-induced heating of the nickel nanoparticles to their Curie temperature. Model calculations confirm the strong correlation between the excitation of surface plasmon modes and laser-induced changes in magnetization., 4 pages, 4 figures

Strong coupling between quantum emitters and surface plasmon polariton modes in metal nanostructures has been extensively studied in recent years. A natural direction of research and a prerequisite for many applications is the possibility of external, in situ manipulation of the strength of the coupling. We review research on active control of surface plasmon–emitter strong coupling phenomena. Active control has been demonstrated for a variety of systems, such as metal nanohole arrays, nanoparticles, rods and dimers, combined with photochromic molecules, J-aggregates, and monolayers of MoS2, WS2, and WSe2. We discuss work on optical switching realized by changing photochromic molecules by UV and visible light between forms that couple strongly or weakly with the electromagnetic field mode of the plasmonic nanostructure. Other forms of optical control such as use of polarization and phase are briefly covered. We review research on electrical, thermal, and chemical active control of light–matter coupling in plasmonic systems.

The spatial and temporal coherence of the fluorescence emission controlled by a quasi-two-dimensional hybrid photonic–plasmonic crystal structure covered with a thin fluorescent-molecular-doped dielectric film is investigated experimentally. A simple theoretical model to describe how a confined quasi-two-dimensional optical mode may induce coherent fluorescence emission is also presented. Concerning the spatial coherence, it is experimentally observed that the coherence area in the plane of the light source is in excess of 49 μm2, which results in enhanced directional fluorescence emission. Concerning temporal coherence, the obtained coherence time is 4 times longer than that of the normal fluorescence emission in vacuum. Moreover, a Young's double-slit interference experiment is performed to directly confirm the spatially coherent emission. This smoking gun proof of spatial coherence is reported here for the first time for the optical-mode-modified emission.

We study lasing in regular arrays made from aluminum nanoparticles. We show that these structures function as laser sources at visible wavelengths, even when scaled to an order of magnitude smaller areas compared to existing literature. The aluminum nanoparticles provide a robust platform for studying lasing in plasmonic systems, even when the optical losses are higher compared to silver or gold.

Lasing at the nanometre scale promises strong light-matter interactions and ultrafast operation. Plasmonic resonances supported by metallic nanoparticles have extremely small mode volumes and high field enhancements, making them an ideal platform for studying nanoscale lasing. At visible frequencies, however, the applicability of plasmon resonances is limited due to strong ohmic and radiative losses. Intriguingly, plasmonic nanoparticle arrays support non-radiative dark modes that offer longer life-times but are inaccessible to far-field radiation. Here, we show lasing both in dark and bright modes of an array of silver nanoparticles combined with optically pumped dye molecules. Linewidths of 0.2 nanometers at visible wavelengths and room temperature are observed. Access to the dark modes is provided by a coherent out-coupling mechanism based on the finite size of the array. The results open a route to utilize all modes of plasmonic lattices, also the high-Q ones, for studies of strong light-matter interactions, condensation and photon fluids., Comment: Accepted for publication in Nature Communications

This chapter introduces the theory behind strong coupling of plasmonic modes, such as surface plasmon polaritons, with electronic transitions that are typical for quantum emitters, such as dye molecules and quantum dots. A brief historical overview of the experimental endeavor of measuring such strong coupling is provided, after which we look more carefully at the dynamics in such systems. We proceed with a more in-depth discussion of strong coupling between emitters and delocalized plasmonic modes, called surface lattice resonances, but not before devoting some space to the ideas and theory behind surface lattice resonances for the readers who might not be familiar with the topic. We end the chapter with an outlook on the potential strong coupling has for new and exciting fundamental phenomena and applications of light on the nanoscale.

We study the spatial coherence properties of a system composed of periodic silver nanoparticle arrays covered with fluorescent organic molecule film [1]. The evolution of spatial coherence of the structure is investigated both in weak and strong coupling regimes by systematically varying the coupling strength between the localized molecular excitons and the collective, delocalized modes of the nanoparticle array known as surface lattice resonances (SLRs). In stark contrast to pure localized excitons, the high degree of spatial coherence is maintained in the strong coupling regime, even when the mode is very exciton-like (80%). The results of our recent luminescence experiments will be presented. The effects of spin-orbit coupling are studied in periodic rectangular arrays of magnetic Ni nanoparticles [2]. We observe SLR modes in which the two directions of the lattice are coupled by the magnetic-field-controllable spin-orbit coupling in the nanoparticles. When breaking the symmetry of the lattice, we find that the optical response shows Fano-type surface lattice resonances whose frequency is determined by the periodicity orthogonal to the polarization of the incident field. In striking contrast, the magneto-optical Kerr response is controlled by the period in the parallel direction. The spectral separation of the response for longitudinal and orthogonal excitations provides versatile tuning of narrow and intense magneto-optical resonances.

openaire: EC/FP7/340748/EU//CODE We report on the optical and magneto-optical response of hybrid plasmonic lattices that consist of pure nickel and gold nanoparticles in a checkerboard arrangement. Diffractive far-field coupling between the individual emitters of the lattices results in the excitation of two orthogonal surface lattice resonance modes. Local analyses of the radiation fields indicate that both the nickel and gold nanoparticles contribute to these collective resonances and, thereby, to the magneto-optical activity of the hybrid arrays. The strong effect of noble metal nanoparticles on the magneto-optical response of hybrid lattices opens up new avenues for the realization of sensitive and tunable magneto-plasmonic nanostructures.

We show strong coupling involving three different types of resonances in plasmonic nanoarrays: surface lattice resonances, localized surface plasmon resonances on single nanoparticles, and excitations of organic dye molecules. We study spatial coherence properties of a plasmonic nanoarray covered with a dye molecule film by a double slit experiment. A continuous evolution of coherence from the weak to the strong coupling regime is observed. Finally, we show with magnetic nanoparticles how the intrinsic spin-orbit coupling of the material interplays with the symmetries of the nanoparticle array, and mention our latest results on light-matter interactions in plasmonic lattices.

Structuring metallic and magnetic materials on subwavelength scales allows for extreme confinement and a versatile design of electromagnetic field modes. This may be used, for example, to enhance magneto-optical responses, to control plasmonic systems using a magnetic field, or to tailor magneto-optical properties of individual nanostructures. Here we show that periodic rectangular arrays of magnetic nanoparticles display surface plasmon modes in which the two directions of the lattice are coupled by the magnetic field-controllable spin–orbit coupling in the nanoparticles. When breaking the symmetry of the lattice, we find that the optical response shows Fano-type surface lattice resonances whose frequency is determined by the periodicity orthogonal to the polarization of the incident field. In striking contrast, the magneto-optical Kerr response is controlled by the period in the parallel direction. The spectral separation of the response for longitudinal and orthogonal excitations provides versatile tuning of narrow and intense magneto-optical resonances., By incorporating magnetic materials into periodic nanostructures, additional control over the magneto-optical response of the system can be introduced. Kataja et al. show that arrays of magnetic nanoparticles exhibit Fano-type surface plasmon resonances with cross-coupling tuned by the lattice symmetry.

We study spatial coherence properties of a system composed of periodic silver nanoparticle arrays covered with a fluorescent organic molecule (DiD) film. The evolution of spatial coherence of this composite structure from the weak to the strong coupling regime is investigated by systematically varying the coupling strength between the localized DiD excitons and the collective, delocalized modes of the nanoparticle array known as surface lattice resonances. A gradual evolution of coherence from the weak to the strong coupling regime is observed, with the strong coupling features clearly visible in interference fringes. A high degree of spatial coherence is demonstrated in the strong coupling regime, even when the mode is very excitonlike (80%), in contrast to the purely localized nature of molecular excitons. We show that coherence appears in proportion to the weight of the plasmonic component of the mode throughout the weak-to-strong coupling crossover, providing evidence for the hybrid nature of the normal modes., 22 pages, 18 figures including supplemental material

The understanding and control of the dynamics of hybrid modes consisting of strongly coupled surface plasmon polaritons and molecular excitations of dye molecules is of great timely interest, as it allows one to tailor interactions between optical signals as needed for active all-optical devices. Here we utilize dye molecules with an especially large Stokes shift to demonstrate the absence of mutual scatterings among the strongly coupled hybrid modes. We employ a quantum mechanical three-level model and show that the hybrid modes decay via dephasing and internal relaxation of the molecules to a fluorescing state of the dye, which can be used as a measure for the decay. Our results provide essential information about the dynamics of the strongly coupled modes.

We report on strong coupling between surface-plasmon polaritons and Rhodamine 6G molecules at room temperature. As a reference to compare with, we first determine the dispersion curve of (uncoupled) surface plasmon polaritons on a 50 nm thick film of silver. Consequently, we determine the dispersion curve of surface plasmon polaritons strongly coupled to Rhodamine 6G molecules, which exhibits vacuum Rabi splitting. Depending on the Rhodamine 6G concentration, we find splitting energies between 0.05 eV and 0.13 eV.

Herein, we experimentally demonstrate surface plasmon polariton (SPP) induced changes in the conductivity of a carbon nanotube field effect transistor (CNT FET). SPP excitation is done via Kretschmann configuration while the measured CNT FET is situated on the opposite side of the metal layer away from the laser, but within reach of the launched SPPs. We observe a shift of 0.4 V in effective gate voltage. SPP-intermediated desorption of physisorbed oxygen from the device is discussed as a likely explanation of the observed effect. This effect is visible even at low SPP intensities and within a near-infrared range. peerReviewed

We report on strong coupling between surface plasmon polaritons (SPP) and Rhodamine 6G (R6G) molecules, with double vacuum Rabi splitting energies up to 230 and 110 meV. In addition, we demonstrate the emission of all three energy branches of the strongly coupled SPP-exciton hybrid system, revealing features of system dynamics that are not visible in conventional reflectometry. Finally, in analogy to tunable-Q microcavities, we show that the Rabi splitting can be controlled by adjusting the interaction time between waveguided SPPs and R6G deposited on top of the waveguide. The interaction time can be controlled with sub-fs precision by adjusting the length of the R6G area with standard lithography methods., Comment: 4 pages, 4 figures

We use molecules to couple light into and out of microscale plasmonic waveguides. Energy transfer, mediated by surface plasmons, from donor molecules to acceptor molecules over ten micrometer distances is demonstrated. Also surface plasmon coupled emission from the donor molecules is observed at similar distances away from the excitation spot. The lithographic fabrication method we use for positioning the dye molecules allows scaling to nanometer dimensions. The use of molecules as couplers between far-field and near-field light offers the advantages that no special excitation geometry is needed, any light source can be used to excite plasmons and the excitation can be localized below the diffraction limit. Moreover, the use of molecules has the potential for integration with molecular electronics and for the use of molecular self-assembly in fabrication. Our results constitute a proof-of-principle demonstration of a plasmonic waveguide where signal in- and outcoupling is done by molecules., 9 pages, 5 figures

We study lasing in arrays of metallic nanoparticles combined with an active medium of dye molecules. We use a model which reduces the generally complicated spatial and temporal dynamics of electromagnetic fields in the array structure to a single ordinary differential equation for an oscillating dipole. By focusing on the most relevant processes, this approximation allows direct physical insight while reducing the computational effort. We benchmark our model against recent experiments and find satisfactory agreement.

A characteristic feature of the state-of-the-art of real-space methods in electronic structure calculations is the diversity of the techniques used in the discretization of the relevant partial differential equations. In this context, the main approaches include finite-difference methods, various types of finite-elements and wavelets. This paper reports on the results of several code development projects that approach problems related to the electronic structure using these three different discretization methods. We review the ideas behind these methods, give examples of their applications, and discuss their similarities and differences., Comment: 39 pages, 10 figures, accepted to a special issue of "physica status solidi (b) - basic solid state physics" devoted to the CECAM workshop "State of the art developments and perspectives of real-space electronic structure techniques in condensed matter and molecular physics". v2: Minor stylistic and typographical changes, partly inspired by referee comments

We demonstrate frequency conversion of surface plasmon polaritons (SPP) by utilizing the coupling between organic dye molecules and SPP. Launching of SPPs into a plasmonic waveguide is done in two ways: by optically excited molecules and by quantum dots (QDs). QDs are demonstrated to overcome the major problem of bleaching occurring with molecules. The SPP propagates tens of micrometers and clear frequency conversion is observed in the SPP spectrum after passing an area of converter molecules. The use of molecules and QDs as elements of all-plasmonic devices has the potential for high integration and use of self-assembly in fabrication.

A μm-scale calorimeter realized by using Schottky junctions as a thermometer is presented. Combined with a hybrid experimental method, it enables simultaneous time-resolved measurements of variations in both the energy and the heat capacity of subnanoliter samples.

We demonstrate a strong coupling between surface plasmon polaritons and Sulforhodamine 101 dye molecules. Dispersion curves for surface plasmon polaritons on samples with a thin layer of silver covered with Sulforhodamine 101 molecules embedded in SU-8 polymer are obtained experimentally by reflectometry measurements and compared to the dispersion of samples without molecules. Clear Rabi splittings, with energies up to 360 and 190 meV, are observed at the positions of the dye absorption maxima. The split energies are dependent on the number of Sulforhodamine 101 molecules involved in the coupling process. Transfer matrix and coupled oscillator methods are used to model the studied multilayer structures with a great agreement with the experiments. Detection of the scattered radiation after the propagation provides another way to obtain the dispersion relation of the surface plasmon polaritons and, thus, provides insight into dynamics of the surface plasmon polariton/dye interaction, beyond the refrectometry measurements. PACS: 42.50.Hz, 33.80.-b, 78.67.-n