Fabrication of a Resonant Waveguide Grating (RWG) with a single-step TiO2 sol-gel technological approach on planar and non-conventional substrate (tube)

Resonant waveguide gratings (RWG), also called Guided-Mode Resonance (GMR) gratings, have been discovered several decades ago, and are known for their possibility to very strongly reflect an incident wave for special configurations of the parameters of the optical setup like wavelength, polarization and incident angle. An RWG consists of a high index waveguide and a periodic corrugation (grating) to couple the waveguide mode.

A simple technological approach combining a photo-patternable sol-gel layer and UV lithography is demonstrated for the fabrication of Resonant Waveguide Gratings (RWG) on planar and cylindrical substrates. The aim is the demonstration of a resonant reflection in TE and TM polarization in the near infrared region (NIR) in a planar and a cylindrical-based resonant waveguide gratings (RWG). In this presentation, we want to show 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 a 8 mm diameter tube, excited by a cylindrical wave. For both configurations, 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 layer, avoiding any etching processes. The reflection spectrum was measured in the near-infrared range and compared to the modeling using the Chandezon method, showing the expected resonant behavior.