Micro-structuration of a sol-gel architecture for channel waveguide / diffraction grating coupling

Abstract A flagship application of miniaturized chemical optical (CO) sensors is the real-time monitoring of cell cultures in the biomedical field. Most of these devices are based on fluorescence variations when a fluorophore encapsulated in the sensor is brought into contact with an analyte. In this context, micro-structured architectures involving light coupling between a channel waveguide and diffraction gratings appear a promising way to propose integrated devices with enhanced detection sensitivity. In this paper, we report for the first time on such micro-structured architecture entirely elaborated through a sol-gel route. This work particularly highlights the potential of a high refractive index titanium oxide based sol-gel photoresist that can be imprinted through a single photolithography step (selective insolation/development) to form a given pattern, thus avoiding multi-step and rather costly traditional lithographic procedures. We firstly present a simplified two-step process taking advantage of this photoresist and leading to micro-structured architectures composed of diffraction gratings imprinted on channel waveguides. Both components of these architectures have been optimized on the basis of opto-geometrical characterizations and modeling. Then channel waveguide/diffraction grating coupling assessments are presented and discussed, showing that light coupling can effectively be achieved in the sol-gel architectures. This work constitutes a first step that opens the route to new CO sensors in channel waveguide configuration.