  Alternative theories of gravity predict up to six distinct polarization modes
for gravitational waves. Strong gravitational lensing of gravitational waves
allows us to probe the polarization content of these signals by effectively
increasing the number of observations from the same astrophysical source. The
lensing time delays due to the multiple observed lensed images combined with
the rotation of the Earth allows for effective non-collocated interferometers
to be defined with respect to the source location and hence probe the
alternative polarization amplitudes with more observations. To measure these
amplitudes, we jointly fit the image observations to a single gravitational
wave signal model that takes into account the image magnifications, time
delays, and polarization mode amplitudes. We show that for certain systems, we
can make a measurement of the relative mode amplitudes for lensed events with
two detectable images.
