  In this study, we examine the phenomenon of photon axion conversion occurring
in the spacetime surrounding a black hole. Specifically, we focus on the
potential existence of a magnetic field around the supermassive black hole
M87*, which could facilitate the conversion of photons into axions in close
proximity to the photon sphere. While photons traverse through the curved
spacetime, they spend time near the photon sphere, where conversion of these
photons into axions takes place. Consequently, this process leads to a decrease
in the intensity of the black hole's photon ring. To explore the possibilities
of detecting these hypothetical axion particles, we propose observing the
photon sphere using higher resolution telescopes. By doing so, we can gain
valuable insights into the conversion mechanism as well as the nature of the
spherically symmetric black hole geometry. Moreover, we also investigate how
the photon ring luminosities are affected if the black hole possesses a charge
parameter. For instance apart from U(1) electric charge, the presence of extra
dimension may induce a {\em tidal charge} with a characteristic signature. It
is important to note that the success of the conversion mechanism relies on the
axion-photon coupling and mass. As a result, the modified luminosity of the
black hole's photon ring offers a valuable means of constraining the axion's
mass and coupling parameter within a certain range. Thus our findings
contribute to a better understanding of photon axion conversion in the
environment of a black hole spacetime and helps us explore the possible
existence of extra spatial dimension.
