  Superfluid has been realized in Helium-4, Helium-3 and ultra-cold atoms. It
has been widely used in making high-precision devices and also in cooling
various systems. There have been extensive experimental search for possible
exciton superfluid (ESF) in semiconductor electron-hole bilayer (EHBL) systems
below liquid Helium temperature. However, exciton superfluid are meta-stable
and will eventually decay through emitting photons. Here we study quantum
nature of photons emitted from the excitonic superfluid (ESF) phase in the
semiconductor EHBL and find that the light emitted from the excitonic
superfluid has unique and unusual features not shared by any other atomic or
condensed matter systems. We show that the emitted photons along the direction
perpendicular to the layer are in a coherent state, those along all tilted
directions are in a two modes squeezed state. We determine the two mode
squeezing spectra, the angle resolved power spectrum, the line shapes of both
the momentum distribution curve (MDC) and the energy distribution curve (EDC).
  From the two photon correlation functions, we find there are photon bunching,
the photo-count statistics is super-Poissonian. We discuss how several
important parameters such as the chemical potential, the exciton decay rate,
the quasiparticle energy spectrum and the dipole-dipole interaction strength
between the excitons in our theory can be extracted from the experimental data
and comment on available experimental data on both EDC and MDC.
