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During the past decade the interactions of fluorophores with metallic particles and surfaces has become an active area of research. These near-field interactions of fluorophores with surface plasmons have resulted in increased brightness and directional emission. However, using metals provide some disadvantages, like quenching at short fluorophore-metal distances, increased rates of energy dissipation due to lossy metals. These unfavorable effects are not expected in dielectrics. In this paper we describe the interactions of fluorophores with one-dimensional (1D) photonic crystals (PCs), which have alternating layers of dielectrics with dimensions that create a photonic bandgap (PBG). Freely propagating light at the PBG wavelength will be reflected. However, similar with metals, we show that fluorophores within near-field distances of the 1DPC interacts with the structure. Our results demonstrated that these fluorophores can interact with both Internal Modes (IM) and Bloch Surface Waves (BSW) of the 1DPC. For fluorophores on the surface of the 1DPC the emission dominantly occurs through the 1DPC and into the substrate. We refer to these two phenomena together as Bragg Grating-Coupled Emission (BGCE). Here we describe our preliminary results on BGCE. 1DPCs are simple to fabricate and can be handled and reused without damage. We believe BGCE provide opportunities for new formats for fluorescence detection and sensing.

We present a direct evidence of Bloch surface waves (BSWs) waveguiding on ultrathin polymeric ridges, supported by near-field measurements. It is demonstrated that near-infrared BSWs sustained by a silicon-based multilayer can be locally coupled and guided through dielectric ridges of nanometric thickness with low propagation losses. Using a conventional prism-based configuration, we demonstrate a wavelength-selective BSW coupling inside and outside the ridge. Such a result can open interesting opportunities in surface wave-mediated sensing applications, where light could be selectively coupled in specific regions defined by nanometric reliefs.KEYWORDS Surface electromagnetic waves, near-field optical microscopy B loch surface waves (BSW) are either TE-or TMpolarized surface modes that can be sustained by truncated stacks of periodically arranged dielectric layers. 1,2 Although BSWs have been known for more than thirty years, they have been recently reconsidered as an alternative to surface plasmon polaritons (SPP), 3 in particular in sensing applications. [4][5][6] Until now, a number of far-field and near-field investigations have been conducted on the coupling of BSW on flat 7-9 and corrugated planar structures. [10][11][12] Here we demonstrate that near-infrared BSWs can be selectively prism-coupled and efficiently guided through an ultrathin polymeric ridge waveguide having thickness < λ/10 realized onto a silicon nitride multilayer. Besides being wavelength scalable and fully compatible with the actual fabrication technologies of integrated photonic and plasmonic structures, the proposed hybrid organic/inorganic structure can provide disruptive opportunities in waveguide-based biosensing schemes, (see, e.g., ref 13) in which the chemical specificity of the sensor might be implemented by functional molecule layers patterned as waveguides with nanometric thickness.In the past decade, a large number of issues connected to the guiding of electromagnetic surface waves (mostly SPP) on a subwavelength scale have been addressed by one branch of plasmonics. 14 Plasmonic waveguides according to different geometries have been proposed mainly for gaining strong (lateral) field confinement while maintaining low propagation losses in view of a high-density packing of integrated photonic circuitry. 15 In addition to guiding mechanisms based on ultrathin metallic membranes, 16 nanoparticles chains, 17,18 nanowires on dielectric substrates, 19 dielectric nanocylinders on metallic films, 20 or V-grooves in metal surfaces, 21 the most popular plasmonic waveguide configurations are constituted by metal-insulator-metal (MIM) 22,23 or insulator-metal-insulator (IMI) 24 structures. Among the latter, we recall the so-called dielectric-loaded surface plasmon polariton waveguides (DLSPPW), 25 in which a dielectric stripe is deposited onto a flat metallic film. The dielectric cladding is thick enough to confine SPP within the ridge, therefore lowering the propagation losses as well as the sensitivity upon external perturbat...

There is a continuing need to increase the brightness and photostability of fluorophores for use in biotechnology, medical diagnostics and cell imaging. One approach developed during the past decade is to use metallic surfaces and nanostructures. It is now known that excited state fluorophores display interactions with surface plasmons, which can increase the radiative decay rates, modify the spatial distribution of emission and result in directional emission. One important example is Surface Plasmon-Coupled Emission (SPCE). In this phenomenon the fluorophores at close distances from a thin metal film, typically silver, display emission over a small range of angles into the substrate. A disadvantage of SPCE is that the emission occur at large angles relative to the surface normal, and at angles which are larger than the critical angle for the glass substrate. The large angles make it difficult to collect all the coupled emission and have prevented use of SPCE with high-throughput and/or array applications. In the present report we describe a simple multi-layer metal-dielectric structure which allows excitation with light that is perpendicular (normal) to the plane and provides emission within a narrow angular distribution that is normal to the plane. This structure consist of a thin silver film on top of a multi-layer dielectric Bragg grating, with no nanoscale features except for the metal or dielectric layer thicknesses. Our structure is designed to support optical Tamm states, which are trapped electromagnetic modes between the metal film and the underlying Bragg grating. We used simulations with the transfer matrix method to understand the optical properties of Tamm states and localization of the modes or electric fields in the structure. Tamm states can exist with zero in-plane wavevector components and can be created without the use of a coupling prism. We show that fluorophores on top of the metal film can interact with the Tamm state under the metal film and display Tamm state-coupled emission (TSCE). In contrast to SPCE, the Tamm states can display either S- or P-polarization. The TSCE angle is highly sensitive to wavelength which suggests the use of Tamm structures to provide both directional emission and wavelength dispersion. Metallic structures can modify fluorophore decay rates but also have high losses. Photonic crystals have low losses, but may lack the enhanced light-induced fields near metals. The combination of plasmonic and photonic structures offers the opportunity for radiative decay engineering to design new formats for clinical testing and other fluorescence-based applications.

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