Bloch Surface Waves in Open Fabry–Perot Microcavities

Thanks to the increasing availability of technologies for thin film deposition, all-dielectric structures are becoming more and more attractive for integrated photonics. As light–matter interactions are involved, Bloch Surface Waves (BSWs) may represent a viable alternative to plasmonic platforms, allowing easy wavelength and polarization manipulation and reduced absorption losses. However, plasmon-based devices operating at an optical and near-infrared frequency have been demonstrated to reach extraordinary field confinement capabilities, with localized mode volumes of down to a few nanometers. Although such levels of energy localization are substantially unattainable with dielectrics, it is possible to operate subwavelength field confinement by employing high-refractive index materials with proper patterning such as, e.g., photonic crystals and metasurfaces. Here, we propose a computational study on the transverse localization of BSWs by means of quasi-flat Fabry–Perot microcavities, which have the advantage of being fully exposed toward the outer environment. These structures are constituted by defected periodic corrugations of a dielectric multilayer top surface. The dispersion and spatial distribution of BSWs’ cavity mode are presented. In addition, the hybridization of BSWs with an A exciton in a 2D flake of tungsten disulfide (WS2) is also addressed. We show evidence of strong coupling involving not only propagating BSWs but also localized BSWs, namely, band-edge and cavity modes

Compressive-shear adhesion characterization of polyvinyl-butyral and ethylene-vinyl acetate at different curing times before and after exposure to damp-heat conditions

Photovoltaic (PV) module efficiency and reliability are two factors that have an important impact on the final cost of the PV electricity production. It is widely accepted that a good adhesion between the encapsulant and the different substrates of a PV module is needed to ensure long-term reliability. Several testing procedures exist that use a metric derived from the force at interface failure to characterize the adhesion. It has, however, not been demonstrated that those metrics relate directly to the interfacial adhesion (defined as the surface energy density needed to break interfacial bonds), and the obtained results usually relate to an apparent adhesion strength. In this work, we describe a new design for compressive-shear testing of polymer layers bonded to rigid substrates. We use it to characterize real interfacial adhesion of ethylene-vinyl acetate (EVA) and polyvinyl-butyral (PVB) to a glass substrate before and after degradation in damp-heat. Our results show that a peak-force based metric is unable to capture the evolution of adhesion through degradation, and a new metric based on the elastic strain energy of the encapsulant is proposed. Moreover, we show that PVB adhesion to glass is much more affected by damp-heat exposure where polymer saturation takes place, in comparison with the adhesion of EVA to glass. The presented characterization protocol is a powerful tool that can help in assessing the reliability of an encapsulant facing specific degradation conditions. Copyright © 2012 John Wiley & Sons, Ltd

Strip-loaded nano-photonics on horizontal slot waveguide

Background: A strip-loaded slot waveguide is a waveguide platform allowing a large amount of degrees of freedom in terms of fabrication. Contrary to other waveguide types where the guiding layer has to be patterned, only the shape of the top layer, usually a polymer, dictates the response of this platform. Methods: We use the Finite Difference Time Domain method to study the field distribution and the modal behavior of light inside such a waveguide when the loading strip is patterned. Results: We present an overview of several photonic-crystal-based structures on a strip-loaded slot waveguide platform. This theoretical study shows how the fundamental mode confined in the horizontal slab slot waveguide interacts with the dielectric loading structures. By investigating the field confinement, one determines the importance of the longitudinal shape over the lateral shape of the loading structure. Through the examples of sidewall corrugation, row of cylindrical or elliptical holes, and random shapes, we show how such a platform can help integration of complex functions in waveguides. Conclusions: Although the spectral features depend strongly on the period and fill factor of the Bragg gratings studied in our case, the material distribution plays a key-role in the mode behavior. This impacts directly on the applications of such a platform for further modulators and sensors, for instance

Modal properties of a strip-loaded horizontal slot waveguide

Abstract Background Channel waveguides have been developed for years to comply with the need for smaller footprint and better integration in photonics circuits. However, they are still suffering from fabrication complexity and optical losses. These two limitations can be addressed by combining two types of channel waveguides, namely strip-loaded and slot waveguide. Methods We present a systematic study of the geometrical parameters of a strip-loaded horizontal slot waveguide and their influence on the characteristics of the device. Simulations and experiments are carried out to understand the behavior of the electromagnetic field inside such a waveguide. In particular, the influence of the high and low refractive index layers and the loading-strip on the key characteristics of the structure, i.e., the confinement factor and the effective index, are investigated theoretically and compared with experimental values. Results The main properties of this waveguide platform are a low lateral index contrast, a high vertical field confinement, and low-propagation losses (1.4 dB/cm). Conclusions Our results show that this platform is highly versatile, easy to fabricate and low-losses. We also show that the geometry of the mode can be tuned to suit the application

Modal properties of a strip-loaded horizontal slot waveguide

Background: Channel waveguides have been developed for years to comply with the need for smaller footprint and better integration in photonics circuits. However, they are still suffering from fabrication complexity and optical losses. These two limitations can be addressed by combining two types of channel waveguides, namely strip-loaded and slot waveguide. Methods: We present a systematic study of the geometrical parameters of a strip-loaded horizontal slot waveguide and their influence on the characteristics of the device. Simulations and experiments are carried out to understand the behavior of the electromagnetic field inside such a waveguide. In particular, the influence of the high and low refractive index layers and the loading-strip on the key characteristics of the structure, i.e., the confinement factor and the effective index, are investigated theoretically and compared with experimental values. Results: The main properties of this waveguide platform are a low lateral index contrast, a high vertical field confinement, and low-propagation losses (1.4 dB/cm). Conclusions: Our results show that this platform is highly versatile, easy to fabricate and low-losses. We also show that the geometry of the mode can be tuned to suit the application