  Exciton-polaritons have become an emerging platform for implementing
non-Hermitian physics. The implementation commonly requires control of both the
real and imaginary parts of the eigenmodes of the system. We present an
experimental method to achieve this purpose using microcavities with
sub-wavelength gratings as reflectors. The reflectivity and reflection phase of
the grating can be changed by its geometric parameters and they determine the
energy and linewidth of the polariton modes. We demonstrate that this method
allows a wide range of possible polariton energy and linewidth, suitable for
implementing non-Hermitian polariton systems with coupled modes.
