  Virtual gain refers to the simulation of real light amplification using
radiation with exponentially decaying amplitude, so that its complex frequency
corresponds to the scattering pole. We theoretically study virtual gain in a
two-level resonant medium for different regimes of light-matter interaction
depending on the radiation intensity. We show that virtual gain at the pole can
be most clearly observed for low intensities, when the medium is absorbing, in
contrast to the saturated medium at high intensities. The efficiency of virtual
gain can be tuned with the light intensity and can be controlled dynamically
through the population inversion of the medium. Our results show that
resonantly absorbing media paradoxically mimics gain-like response, which admit
a number of related phenomena and methods to mold both optical signals and
material properties without relying on instability-prone gain media.
