  The occurrence of exceptional points (EPs) is a fascinating non-Hermitian
feature of open systems. A level-repulsion phenomenon between two complex
states of an open system can be realized by positioning an EP and its
time-reversal (T) conjugate pair in the underlying parameter space. Here, we
report the fascinating nonreciprocal response of such two conjugate EPs by
using a dual-mode planar waveguide system having two T-symmetric active
variants concerning the transverse gain-loss profiles. We specifically reveal a
comprehensive all-optical scheme to achieve correlative nonreciprocal light
dynamics by using the reverse chirality of two dynamically encircled conjugate
EPs in the presence of local nonlinearity. A specific nonreciprocal correlation
between two designed T-symmetric waveguide variants is established in terms of
their unidirectional transfer of light with a precise selection of modes. Here,
the unconventional reverse chiral properties of two conjugate EPs allow the
nonreciprocal transmission of two selective modes in the opposite directions of
the underlying waveguide variants. An explicit dependence of the nonlinearity
level on a significant enhancement of the nonreciprocity in terms of an
isolation ratio is explored by investigating the effects of both local
Kerr-type and saturable nonlinearities (considered separately). The physical
insights and implications of harnessing the properties of conjugate EPs in
nonlinear optical systems can enable the growth and development of a versatile
platform for building nonreciprocal components and devices.
