  Complex 3D integration of photonic and electronic integrated circuits is of
particular interest to carry the photonics roadmap and to address challenges
but involves mechanical stress, often detrimental for the behavior of optical
components. Existing experiments failed to carefully analyze the stress in such
integrated optical devices due to the requirement in terms of feature sizes,
few hundreds of nanometers, and 3D-stacked integration. We present for the
first time the characterization of the stress tensor of a silicon waveguide
using Integrated Raman Spectroscopy (IRS). This experimental technique is
directly sensitive to the effective stress, which involves changes in optical
properties of the guided mode, at the working wavelength and polarization state
of the photonic component. The experimental stress tensor is in good agreement
with simulations.
