  The nonclassical feature of photons in the open finite-size Dicke model is
investigated via the two-photon correlation function. The quantum dressed
master equation combined with the extended coherent photonic states is applied
to analyze the dissipative dynamics of both the photons and qubits. The
anti-bunching to bunching transition of photons is clearly observed by tuning
the qubit-photon coupling strength. The optimal qubits number is unraveled to
enhance the two-photon correlation function. Moreover, the temperature bias of
thermal baths induces significant two-photon bunching signature with deep
strong qubit-photon interaction.
