  The past few years have witnessed growing interests in exceptional points
(EPs) in various domains, including photonics, acoustics and electronics.
However, EPs have mainly been realized based on the degeneracy of resonances of
physical systems; distinct degeneracies occur relating to the absorption
properties of waves, with distinct physical manifestations. Here we demonstrate
this physically different kind of exceptional point, by engineering
degeneracies in the absorption spectrum of optical microcavities with
dissipation. We experimentally distinguish the conditions to realize a resonant
EP and an absorbing EP. Furthermore, when the optical loss is optimized to
achieve perfect absorption at such an EP, we observe an anomalously broadened
lineshape in the absorption spectra, as predicted by theory. The distinct
scattering properties enabled by this type of EP creates new opportunities for
both the fundamental study and applications of non-Hermitian singularities.
