Theoretical modelling of superradiant lasers and other open quantum resonant systems

An approach for solving the stationary nonlinear quantum Langevin equations for micro-lasers and other small resonant optical devices (for nonlinear optics, plasmonics etc.) is presented. The method uses frequency dependent operators and calculates the mean fluctuation power spectra and photon number. Various approximations for finding analytical expressions are shown. Results for thresholdless lasing, collective Rabi splitting, super-thermal photon statistics and the power increase by the population fluctuations for the superradiant lasers are discussed.