  Exceptional points(EPs), branch points of complex energy surfaces at which
eigenvalues and eigenvectors coalesce, are ubiquitous in non-Hermitian systems.
Many novel properties and applications have been proposed around the EPs. One
of the important applications is to enhance the detection sensitivity. However,
due to the lack of single-handed superchiral fields, all of the proposed
EP-based sensing mechanisms are only useful for the non-chiral discrimination.
Here, we propose theoretically and demonstrate experimentally a new type of EP,
which is a called radiation vector EP, to fulfill the homogeneous superchiral
fields for chiral sensing. This type of EP is realized by suitably tuning the
coupling strength and radiation losses for a pair of orthogonal polarization
modes in the photonic crystal slab. Based on the unique modal-coupling property
at the vector EP, we demonstrate that the uniform superchiral fields can be
generated with two beams of lights illuminating on the photonic crystal slab
from opposite directions. Thus, the designed photonic crystal slab, which
supports the vector EP, can be used to perform surface-enhanced chiral
detection. Our findings provide a new strategy for ultrasensitive
characterization and quantification of molecular chirality, a key aspect for
various bioscience and biomedicine applications.
