Tantalum Pentoxide Slot Waveguides for Waveguide Enhanced Raman Spectroscopy

Waveguide enhanced Raman spectroscopy (WERS) is a promising technique for the sensing of chemical compounds, thanks to the extended interaction volume and tight confinement of light using photonic waveguides [1] . However, it is sometimes insufficiently sensitive for applications where the relevant concentrations are low. There are different methods to improve the signal intensity, including using high-index-contrast (HIC) waveguides other than Si 3 N 4 . It has been shown by Raza et al. [2] that the Ta 2 O 5 platform is beneficial for WERS, as Ta 2 O 5 strip waveguide enhances the signal without introducing more waveguide background than Si 3 N 4 . The Ta 2 O 5 platform still has further potential, as the strip waveguide is not optimal for evanescent sensing compared to the slot waveguide, for which the electric field is mostly confined in the cladding [3] . In this work, we demonstrate a systematic study of Ta 2 O 5 slot waveguides for WERS and compare it to Si 3 N 4 slot waveguides.