  For direct imaging of exoplanets, Scalar Vortex Coronagraphs (SVCs) are an
attractive alternative to the popularly used Vector Vortex Coronagraphs (VVCs).
This is primarily because they are able to induce the same phase ramp
regardless of the incoming light's polarization state. We tested a set of
stepped SVC staircase masks in the Exoplanet Technology Laboratory (ET Lab) at
Caltech on the High-Contrast Spectroscopy Testbed (HCST). Here we present some
preliminary findings of their starlight suppression ability, achieving raw
contrasts on the order of 1e-5 for 7 to 9 lambda/D. We also characterized their
chromatic performance and performed wavefront control to achieve preliminary
contrasts on the order of 1e-7 with EFC. These initial experimental results
with SVCs have shown scalar vortex technology has a great potential for future
exoplanet direct imaging missions.
