Reference pads for miniature integrated optical sensors

Placing multiple sensing regions (sensing pads) on a single chip is a powerful means for referencing and multicomponent analysis by miniature integrated optical sensors. On-chip referencing is of utmost importance for practical (bio-)chemical sensors to compensate or correct for unspecific effects and external disturbances. Results of experimental and theoretical investigations are reported for the temperature effect as an important example of an unspecific effect that is present and relevant for the majority of practical applications. On-chip referencing experiments have been performed for highly sensitive grating coupler sensor chips consisting of compact TiO2 and Ta2O5 waveguiding films on fused silica and for TiO2 films on replicated polycarbonate substrates. The results are not only relevant for grating coupler sensor chips but also for many other evanescent-wave sensors. The results are the basis for realizing sensor chips with significantly enhanced effective sensitivities.