Engineering Waveguide Nonlinear Effective Length via Low Index Thin Films.

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