  On-chip super-resolution optical microscopy is an emerging field relying on
waveguide excitation with visible light. Here, we investigate two commonly used
high-refractive index waveguide platforms, tantalum pentoxide (Ta$_2$O$_5$) and
silicon nitride (Si$_3$N$_4$), with respect to their background with excitation
in the range 488-640 nm. The background strength from these waveguides were
estimated by imaging fluorescent beads. The spectral dependence of the
background from these waveguide platforms was also measured. For 640 nm
wavelength excitation both the materials had a weak background, but the
background increases progressively for shorter wavelengths for Si3N4. We
further explored the effect of the waveguide background on localization
precision of single molecule localization for direct stochastic optical
reconstruction microscopy (dSTORM). An increase in background for Si$_3$N$_4$
at 488 nm is shown to reduce the localization precision and thus the resolution
of the reconstructed images. The localization precision at 640 nm was very
similar for both the materials. Thus, for shorter wavelength applications
Ta$_2$O$_5$ is preferable. Reducing the background from Si$_3$N$_4$ at shorter
wavelengths via improved fabrication will be worth pursuing.
