his system exhibits a wide range of behaviour and is potentially an easily tunable source of single-mode squeezing, entangled states and states which exhibit the EPR paradox. The spatial separation of the output modes means that they do not have to be separated by optical devices before measurements can be made, along with the unavoidable losses which would result from this procedure. The entangled beams produced can be degenerate in both frequency and polarisation, unlike those of the nondegenerate OPO, and would exit the cavity at spatially separated locations. Th