  In this study, we propose the application of non-Hermitian photonic crystals
(PCs) with anisotropic emissions. Unlike a ring of exceptional points (EPs) in
isotropic non-Hermitian PCs, the EPs of anisotropic non-Hermitian PCs appear as
lines symmetrical about the $\Gamma$ point. The non-Hermitian Hamiltonian
indicates that the formation of EPs is related to the non-Hermitian strength.
The real spectrum appears in the $\Gamma$Y direction and has been validated as
the complex conjugate medium (CCM) by effective medium theory (EMT). But for
the $\Gamma$X direction, EMT indicates that the effective refractive index has
a large imaginary part, which forms an evanescent wave inside the PCs. Thence,
coherent perfect absorber (CPA) and laser effects can be achieved in the
directional emission of the $\Gamma$Y. The outgoing wave in the $\Gamma$X
direction is weak, which can significantly reduce the losses and
electromagnetic interference caused by the leakage waves. Furthermore, the
non-Hermitian PCs enable many fascinating applications such as signal
amplification, collimation, and angle sensors.
