Λ-scheme feedback spectroscopy

We investigate probe-pump spectroscopy of a Λ-system, with one of the fields' phase being controlled by a feedback loop. The feedback is trigged by modified photo-detection events organized by means of a special unravelling of master equations. The steady-state of the system is obtained and analyzed, and works of the fields per unit time are evaluated. It is shown that the properties of dark resonances can effectively be controlled by the choice of the events that trig feedback action and by the fields' amplitudes. There revealed surprising peculiarities of the fields' work as a function of their amplitudes.