Photonic components are superior to electronic ones in terms of operational bandwidth, but the diffraction limit of light poses a significant challenge to the miniaturization and high-density integration of optical circuits. The main approach to circumvent this problem is to exploit the hybrid nature of surface plasmon polaritons (SPPs), which are light waves coupled to free electron oscillations in a metal that can be laterally confined below the diffraction limit using subwavelength metal structures. However, the simultaneous realization of strong confinement and a propagation loss sufficiently low for practical applications has long been out of reach. Channel SPP modes--channel plasmon polaritons (CPPs)--are electromagnetic waves that are bound to and propagate along the bottom of V-shaped grooves milled in a metal film. They are expected to exhibit useful subwavelength confinement, relatively low propagation loss, single-mode operation and efficient transmission around sharp bends. Our previous experiments showed that CPPs do exist and that they propagate over tens of micrometres along straight subwavelength grooves. Here we report the design, fabrication and characterization of CPP-based subwavelength waveguide components operating at telecom wavelengths: Y-splitters, Mach-Zehnder interferometers and waveguide-ring resonators. We demonstrate that CPP guides can indeed be used for large-angle bending and splitting of radiation, thereby enabling the realization of ultracompact plasmonic components and paving the way for a new class of integrated optical circuits.

We present a study on the far-field patterns of light transmitted through sub-wavelength metallic hole-arrays. Spectral imaging measurements are used here on hole arrays for the first time. It provides both spatial and spectral information of the transmission in far-field. The visibility of the images, measured in two illumination modes: Köhler and collimated, is calculated for different planes in and out of focus. The transmission under collimated illumination reveals that 75% of the beam if non-divergent. The results are in agreement with the low divergence measured by Lezec [Science 297, 820 (2002)].

Electromagnetic vacuum fields are omnipresent in our universe, inducing many events such as spontaneous emission, Lamb shift, and Van der Waals forces. As demonstrated here, a chemical reaction can be influenced by strongly coupling the energy landscape governing the reaction pathway to vacuum fields in an optical cavity (see picture; MC=merocyanine).

Many chemical methods have been developed to favor a particular product in transformations of compounds that have two or more reactive sites. We explored a different approach to site selectivity using vibrational strong coupling (VSC) between a reactant and the vacuum field of a microfluidic optical cavity. Specifically, we studied the reactivity of a compound bearing two possible silyl bond cleavage sites—Si–C and Si–O, respectively—as a function of VSC of three distinct vibrational modes in the dark. The results show that VSC can indeed tilt the reactivity landscape to favor one product over the other. Thermodynamic parameters reveal the presence of a large activation barrier and substantial changes to the activation entropy, confirming the modified chemical landscape under strong coupling.

The ground‐state deprotection of a simple alkynylsilane is studied under vibrational strong coupling to the zero‐point fluctuations, or vacuum electromagnetic field, of a resonant IR microfluidic cavity. The reaction rate decreased by a factor of up to 5.5 when the Si−C vibrational stretching modes of the reactant were strongly coupled. The relative change in the reaction rate under strong coupling depends on the Rabi splitting energy. Product analysis by GC‐MS confirmed the kinetic results. Temperature dependence shows that the activation enthalpy and entropy change significantly, suggesting that the transition state is modified from an associative to a dissociative type. These findings show that vibrational strong coupling provides a powerful approach for modifying and controlling chemical landscapes and for understanding reaction mechanisms.

Organic semiconductors have generated considerable interest for their potential for creating inexpensive and flexible devices easily processed on a large scale [1][2][3][4][5][6][7][8][9][10][11]. However technological applications are currently limited by the low mobility of the charge carriers associated with the disorder in these materials [5][6][7][8]. Much effort over the past decades has therefore been focused on optimizing the organisation of the material or the devices to improve carrier mobility. Here we take a radically different path to solving this problem, namely by injecting carriers into states that are hybridized to the vacuum electromagnetic field. These are coherent states that can extend over as many as 10 5 molecules and should thereby favour conductivity in such materials. To test this idea, organic semiconductors were strongly coupled to the vacuum electromagnetic field on plasmonic structures to form polaritonic states with large Rabi splittings ∼ 0.7 eV. Conductivity experiments show that indeed the current does increase by an order of magnitude at resonance in the coupled state, reflecting mostly a change in field-effect mobility as revealed when the structure is gated in a transistor configuration. A theoretical quantum model is presented that confirms the delocalization of the wave-functions of the hybridized states and the consequences on the conductivity. While this is a proof-of-principle study, in practice conductivity mediated by light-matter hybridized states is easy to implement and we therefore expect that it will be used to improve organic devices. More broadly our findings illustrate the potential of engineering the vacuum electromagnetic environment to modify and to improve properties of materials.Light and matter can enter into the strong coupling regime by exchanging photons faster than any competing dissipation processes. This is normally achieved by placing the material in a confined electromagnetic environment, such as a Fabry-Perot (FP) cavity composed of two parallel mirrors that is resonant with an electronic transition in the material. Alternatively, one can use surface plasmon resonances as in this study. Strong coupling leads to the formation of two hybridized light-matter polaritonic states, P+ and P-, separated by the so-called Rabi splitting, as illustrated in Figure 1a. According to quantum electrodynamics, in the absence of dissipation, the Rabi splitting for a single molecule is given bywhere ω is the cavity resonance or transition energy ( the reduced Planck constant), 0 the vacuum permittivity, v the mode volume, d the transition dipole moment of the material and n ph the number of photons present in the system. The last term implies that, even in the dark, the Rabi splitting has a finite value which is due to the interaction with the vacuum electromagnetic field. This vacuum Rabi splitting can be further increased by coupling a large number N of oscillators to the electromagnetic mode since Ω N R ∝ √ N [12]. In this ensemble coupling, in addition to P+ an...

We present results of the transmitted, reflected, and absorbed power associated with the enhanced transmittance of light through a silver film pierced by a periodic array of subwavelength holes. Comparing experimentally acquired dispersion curves under different polarization conditions shows that the transmission features of the array are consistent with p-polarized resonant modes of the structure. By exploring the regime in which no propagating diffracted orders are allowed, we further show that the transmittance maxima are associated with both reflectance minima and absorption maxima. These new results provide strong experimental evidence for transmission based on diffraction, assisted by the enhanced fields associated with surface plasmon polaritons. DOI: 10.1103/PhysRevLett.92.107401 PACS numbers: 78.20.Ci, 41.20.Jb, 42.25.Fx, 73.20.Mf The observation of the enhanced transmission of light through a metallic film perforated by an array of subwavelength holes [1] sparked a wealth of research seeking to explain the underlying physics. For light of wavelength , a hole less than =2 in diameter in a thick metal film does not support any propagating modes; energy can propagate only by an evanescent tunneling process leading to very weak transmittance -in marked contrast to the experimental observations.Initial explanations considered coupling of the incident light via diffraction to surface plasmon polariton (SPP) modes of the metallic structure [1,2]. Many different theoretical approaches have since been adopted, all replicating the normal incidence transmission spectra [3][4][5][6][7]; consequently, more than just the normal incidence transmission spectrum needs to be explored if one is to obtain a clearer picture of the underlying physics. Despite a convergence of views among many theorists that the enhanced transmission involves multiple diffraction enhanced by SPPs [5][6][7][8][9], there remains some controversy surrounding the transmission mechanism; not all authors agree that surface plasmons are involved. (Note that explanations based on results from 1D arrays of slits cannot be used, and the physics is very different; sub-=2 slits can support propagating modes, while sub-=2 holes cannot [10].) As noted elsewhere [8], the experimental evidence obtained thus far is consistent with the involvement of SPPs rather than conclusive about their involvement. We present new experimental data not just of the transmittance, but also of the reflectivity and absorbance. We investigate two unexplored far-field signatures of SPPs in this context, their polarized nature and their dissipative character; we are thus able to identify the role played by SPPs in the transmission process.Diffraction is central to the transmission process. Diffraction of the incident plane wave by the array produces waves with the required evanescent character; diffraction of the transmitted evanescent wave on the far side of the array then produces the propagating transmitted light. However, these diffraction processes are independent of the...

We report on realization of channel plasmon-polariton (CPP) propagation along a subwavelength metal groove. Using imaging with a near-field microscope and end-fire coupling with a tapered fiber connected to a tunable laser at telecommunication wavelengths (1425-1620 nm), we demonstrate low-loss (propagation length approximately 100 microm) and well-confined (mode width approximately 1.1 microm) CPP guiding along a triangular 0.6 microm-wide and 1 microm-deep groove in gold. We develop a simple model based on the effective-index method that accounts for the main features of CPP guiding and provides a clear physical picture of this phenomenon.