  We study the evolution of photon injections with a power-law type spectrum
inserted at various epochs of the universe, and obtain constraints on their
parameter space from multiple different cosmological probes. Our work is
motivated by the realistic possibility of having extended photon spectra from
astrophysical and exotic sources. Going beyond a $\delta$-function like
approximation, the physics becomes richer and the constraining power of
cosmological probes starts to depend on the photon injection history in a
complex way. As a toy model, we first consider a decaying particle scenario,
and then generalize to a more model independent power law type injection in
redshift. Different combinations of our parameters can be mapped to a wide
variety of realistic astrophysical and exotic sources, providing useful
benchmarks for study in future work.
