Facultad de Ciencias de la Actividad Física y del Deporte (INEF)(UPM)
Abstract
For biosensing applications where small refractive index variations of the surrounding medium are monitored, light needs to have a strong interaction with such a surrounding biological medium. This is not the case for classical rib and strip waveguides where light is predominantly guided in the high index material. However, in slot waveguides, light is confined in a low index slot region sandwiched between two high index rails and due to the discontinuity of the electric field at the interface between the rails and slot, a significant fraction of the electromagnetic field is localized in the slot. As such slot waveguides present an interesting alternative for biosensing applications especially when made using silicon nitride which permits slot widths of up to 200nm and as such reachable fabrication tolerances, and reduced propagation losses compared to silicon slot waveguides with its higher refractive index contrast. Furthermore, for biosensing, the wider slot facilitates sample transport and using a multiple-slot structure, further enhancement of the optical confinement in low index slot regions is possible. In this paper we present work in progress of theoretical modeling for strip, slot and multiple-slot waveguides and compare their characteristics for sensing purposes
