Guided Bloch Surface Waves on Ultrathin Polymeric Ridges

Abstract

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...

Leakage radiation interference microscopy

“…Moreover, Fig. 4(b) exhibits a corresponding BSW phase distribution, wherein the BSW propagation is revealed by a periodic sawtooth phase profile, as reported elsewhere [20]. By combining the amplitude and phase mappings, a complex electromagnetic field distribution can be obtained, whose real part is illustrated in Fig.…”

Detection of protein aggregation with a Bloch surface wave based sensor

“…Other features specific to BSW, such as long-range guiding of surface waves [27], are of particular interest. The ability to use alternative materials as a guiding layer, such as teflon, or other biologically inert substances, is an important advantage with respect to SPR based sensors.…”

Room temperature Bloch surface wave polaritons

“…[10,11] Such Bloch surface wave polaritons (BSWP), [12] i.e. mixed excitations bound to the surface of the Bragg mirror,-which exploit the confinement of the optical mode due to total internal reflection as weel as a photonic bandgap-could be exploited for prospective polariton devices with high efficiency and controlled long range propagation, or for applications requiring high surface sensitivity such as optical sensors, [13,14] with clear advantages over alternative structures where metal deposition is required. [15,16] In this letter we report on the experimental demonstra- tion of strong light-matter coupling between J-aggregate excitons with Bloch surface waves (BSW) at the interface between a SiO 2 /TiO 2 Bragg mirror and an index matching homogeneous medium.…”