Effects of Polariton Energy Renormalisation in the Microcavity Optical   Parametric Oscillator
  The CW microcavity optical parametric oscillator (OPO) state is investigated using a theoretical treatment which includes the contributions of the pump, signal and idler populations to the renormalisation of the polariton energies (the `blue-shift'). The theory predicts the pumping conditions under which the OPO switches on, showing that a pump angle > 10 degrees is required, but there is no particular significance to the `magic-angle' where pump, signal and idler are all on resonance. The signal and idler renormalisation contributions also causes the signal emission to be driven towards the normal direction as the pump power increases above threshold. 
D. M. Whittaker