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One-step nanoimprinted Bragg grating sensor based on hybrid polymers

: Förthner, Michael; Girschikofsky, Maiko; Rumler, Maximilian; Stumpf, Florian; Rommel, Mathias; Hellmann, Ralf; Frey, Lothar


Sensors and Actuators. A 283 (2018), S.298-304
ISSN: 0924-4247
Deutsche Forschungsgemeinschaft DFG
Bragg-Gitter-Sensoren auf Basis von Hybridpolymeren - Grundlegende Untersuchungen und Realisierung
Fraunhofer IISB ()
Bragg Grating; SCIL; nanoimprint; temperature sensor; refractive index sensing

Bragg grating sensors are used for real-time analysis of gases or liquids. Complex processing methods are typically required for the sensor fabrication. A reduction of process steps and costs during their fabrication is essential in order to broaden the field of application. Within this work, we demonstrate an innovative process for a one-step fabrication of integrated Bragg grating sensors and their successful application for temperature and refractive index sensing. UV-enhanced substrate conformal imprint lithography (UV-SCIL) is used to replicate surface relief Bragg grating (SBG) sensors on a full wafer scale. Multiple chips of a planar waveguide system including couplers and junctions were etched into a silicon wafer. Nanostructured SBGs were locally added on the waveguides by focused ion beam processing. The sensor structures were replicated by UV-SCIL into a commercially available hybrid polymer (OrmoComp®). Reflection measurements with different Bragg gratings were performed and compared to simulations. The results reveal narrow-band Bragg reflections, coinciding with the simulations. Further, the temperature dependence of the SBGs was investigated. The imprinted grating structures featured a very high temperature sensitivity of −202 pm/°C. The sensor response to a varying refractive index of the surrounding medium was determined for index matching liquids and aqueous solutions.