  We propose a scheme to enhance the sensitivity of Non-Hermitian
optomechanical mass-sensors. The benchmark system consists of two coupled
optomechanical systems where the mechanical resonators are mechanically
coupled. The optical cavities are driven either by a blue or red detuned laser
to produce gain and loss, respectively. Moreover, the mechanical resonators are
parametrically driven through the modulation of their spring constant. For a
specific strength of the optical driving field and without parametric driving,
the system features an Exceptional Point (EP). Any perturbation to the
mechanical frequency (dissipation) induces a splitting (shifting) of the EP,
which scales as the square root of the perturbation strength, resulting in a
sensitivity-factor enhancement compared with conventional optomechanical
sensors. The sensitivity enhancement induced by the shifting scenario is weak
as compared to the one based on the splitting phenomenon. By switching on
parametric driving, the sensitivity of both sensing schemes is greatly
improved, yielding to a better performance of the sensor. We have also
confirmed these results through an analysis of the output spectra and the
transmissions of the optical cavities. In addition to enhancing EP sensitivity,
our scheme also reveals nonlinear effects on sensing under splitting and
shifting scenarii. This work sheds light on new mechanisms of enhancing the
sensitivity of Non-Hermitian mass sensors, paving a way to improve sensors
performance for better nanoparticles or pollutants detection, and for water
treatment.
