  Novel photonic nanowires were fabricated using low-index materials and tested
in the near-infrared spectrum to assess their nonlinear optical properties. In
this work, we argue the need to redefine the standard nonlinear figure of merit
in terms of nonlinear phase shift and optical transmission for a given
propagation distance. According to this new metric, our devices largely
outperform all established platforms for devices with a linear footprint in the
range of 50 to 500 um, which is demonstrated to be an outstanding technological
gap. For 85 fs pulses, with carrier wavelength at 1480nm and sub-uW power
levels, a spectral broadening exceeding 80% of the initial bandwidth was
recorded over a propagation length of just 50 um. Leveraging on CMOS-compatible
processes and well-established materials such as silicon, silica, and indium
tin oxide, our devices bring great promise for developing alternative
all-optical devices with unparalleled nonlinear performances within the
aforementioned range.
