Resonant waveguide grating fabrication on planar and cylindrical substrates using a photosensitive TiO 2 sol-gel approach

A single-step sol-gel technological approach combining sol-gel layer development and UV lithography is demonstrated for the fabrication of resonant waveguide gratings (RWG) on planar and cylindrical substrates. The aim of this article is the demonstration of a resonant reflection in TE and TM polarization in the near-infrared region (NIR) in a planar and in cylindrical-based resonant waveguide gratings (RWG). In this work, we start with a planar corrugated waveguide structure excited by a planar wave and demonstrate this concept to a circularly symmetrical waveguide applied to the inside wall of an 8 mm diameter tube, excited by a cylindrical wave. For both configurations, the same TiO2 sol-gel layer is used for the high index waveguide layer and for the grating printing thanks to the UV photosensitivity property of the sol-gel layers, avoiding any etching processes. The reflection spectrum was measured in the near-infrared range and compared to the modeling, showing the expected resonant behavior.