  We have investigated theoretically the tuning characteristics of a Josephson
junction within a microcavity for one-photon spontaneous emission and for
one-photon and two-photon stimulated emission. For spontaneous emission, we
have established the linear relationship between the magnetic induction and the
voltage needed to tune the system to emit at resonant frequencies. For
stimulated emission, we have found an oscillatory dependence of the emission
rate on the initial Cooper pair phase difference and the phase of the applied
field. Under specific conditions, we have also calculated the values of the
applied radiation amplitude for the first few emission maxima of the system and
for the first five junction-cavity resonances for each process. Since the
emission of photons can be controlled, it may be possible to use such a system
to produce photons on demand. Such sources will have applications in the fields
of quantum cryptography, communications and computation.
