  Photonic integrated circuits are a paramount platform for optoelectronics and
nonlinear optics, enabling high confinement nonlinear interactions, where
advanced waveguide dispersion engineering can be leveraged to tailor broadband
nonlinear processes, supercontinuum generation, soliton formation and joint
spectral amplitudes of photon pairs. Accurately measuring dispersion is
therefore crucial for achieving efficient nonlinear and quantum devices. Here
we develop a dual comb spectroscopy methodology suitable for dispersion
measurements on photonic integrated circuits at telecom wavelengths and apply
it to the characterization of lithium niobate on insulator ridge waveguides,
mapping group velocity dispersion for fundamental TE and TM modes as a function
of waveguide top-width. This work paves the way for the broader deployment of
dual comb spectroscopy as a characterization tool for a broad range of photonic
integrated circuit components on different nanophotonic platforms.
