Abstract
Recent studies have shown that evanescent Raman spectroscopy using a silicon nitride (SiN)
nanophotonic waveguide platform has higher signal enhancement when compared to free-space
systems. However, signal-to-noise ratio from the waveguide at a low analyte concentration is
constrained by the shot-noise from the background light originating from the waveguide itself.
Hence, understanding the origin and properties of this waveguide background luminescence (WGBL)
is essential to developing mitigation strategies. Here, we identify the dominating component of
the WGBL spectrum composed of a broad Raman scattering due to momentum selection-rule
breaking in amorphous materials, and several peaks specific to molecules embedded in the core.
We determine the maximum of the Raman scattering efficiency of the WGBL at room temperature
for 785 nm excitation to be 4.5 1 10..9 cm..1sr..1, at a Stokes shift of 200 cm..1. This efficiency
decreases monotonically for higher Stokes shifts. Additionally, we also demonstrate the use of slotted
waveguides and quasi-transverse magnetic polarization as some mitigation strategies. Related Research Topics
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