  We investigate a semiconductor $p$-$n$ junction in contact with
superconducting leads that is operated under forward bias as a light-emitting
diode. The presence of superconductivity results in a significant increase of
the electroluminescence in a certain frequency window. We demonstrate that the
tunneling of Cooper pairs induces an additional luminescence peak on resonance.
There is a transfer of superconducting to photonic coherence which results in
the emission of entangled photon pairs and squeezing of the fluctuations in the
quadrature amplitudes of the emitted light. The squeezing angle can be
electrically manipulated by changing the relative phase of the order parameters
in the superconductors. We finally derive the conditions for lasing in the
system and show that the laser threshold is reduced due to superconductivity.
This shows how macroscopic coherence of a superconductor can be used to control
the properties of light.
