  Pseudothermal light by scattering laser light from rotating groundglass has
been extensively employed to study optical coherence in both classical and
quantum optics ever since its invention in 1960s. In this paper, we will show
that by replacing the invariant intensity laser light in pseudothermal light
source with intensity modulated laser light, superbunching pseudothermal light
can be obtained. Two-photon interference in Feynman's path integral theory is
employed to interpret the phenomenon. Two-photon superbunching is
experimentally observed by employing common instruments in optical laboratory.
The proposed superbunching pseudothermal light is helpful to understand the
physics of two-photon bunching and superbunching, and the difference between
classical and quantum interpretations of the second- and higher-order
interference of light.
