Two-photon lasing stimulated by collective modes

Considering the resonator losses in photon pairs the coherence between the photon pairs as the function of number of bimodes is studied. Taking into account the big number of resonator bimodes in which the photon pairs with fixed energy and phase are generated, it is demonstrated that the coherence between the pairs of photons remains larger than the coherence between individual photons. It is shown that the ignition of two-photon lasing from vacuum fluctuations increases with the increase in the number of resonator modes. This effect can be regarded as a collective phenomenon between the resonator bimodes in which the pairs of entangled photons are generated.