BSWs are non-radiative electromagnetic waves confined at the interface between a truncated periodic dielectric multilayer and a surrounding media. As an alternative to SPPs (Surface Plasmon Polaritons), BSWs show dramatically enhanced propagation lengths up to several millimeters range and provide new optical opportunities such as the possibility to obtain TE or TM-polarized surface waves. They have found numerous applications in vapor sensing, biosensing, fluorescence detection and imaging, and integrated optics.
In this work, we propose a 1DPhC with a thin film of LiNbO3 (TFLN) as the top layer of the multilayer structure. The bonding of LiNbO3 into the 1DPhC structure brings anisotropy and nonlinear properties into the whole crystal allowing the tunability of the BSW devices.
Here we present 1DPhCs, which are able to sustain surface waves at the LiNbO3/air interface. Two different geometries have been studied, fabricated and optically characterized. The first one is based on the LiNbO3 membrane suspended in air and the second one is held by a stable glass platform.
The multilayer of the membrane based crystal is as following: air/6 pairs of Si3N4(200nm) and SiO2(215nm)/TFLN(1.1μm) – polished from bulk LN/air. The multilayer of the glass supported crystal is as following: glass/UV glue/6 pairs of Si3N4(220 nm) and SiO2(490nm)/TFLN(386nm)/air. 1DPhCs were characterized in Kretschmann configuration at visible and IR wavelengths.
Bloch surface waves (BSWs) are electromagnetic surface waves which can be excited at the interface between periodic dielectric multilayer and a surrounding medium. In comparison with surface plasmon polaritons these surface states perform high quality factor due to low loss characteristics of dielectric materials and can be exited both by TE and TM polarized light. A platform consisting of periodic stacks of alternative SiO2 and Si3N4 layers is designed and fabricated to work at the wavelength of 1.55 µm. The platform has an application in sensing and in integrated optics domain. A standard way of BSW excitation is coupling via Kretschmann configuration, but in this work we investigate a grating coupling of BSWs. Grating parameters are analytically and numerically optimized by RCWA and FDTD methods in order to obtain the best coupling conditions. The light is launched orthogonally to the surface of the photonic crystal and the grating. Due to a special grating configuration we demonstrate directionality of the BSW propagation depending on polarization of the incident light. The structure was experimentally realized on the surface of the photonic crystal by FIB milling. Experimental results are in a good agreement with a theory. The investigated configuration can be successfully used as a BSW launcher in on-chip all-optical integrated systems and work as a surface wave switch or modulator.