Quantum synchronization in a cavity

[Danny Boy]

I am currently studying quantum synchronization. I am reviewing a https://www.researchgate.net/publication/251232415_Quantum_Synchronization_of_Two_Ensembles_of_Atoms which describes quantum synchronization of two ensembles in a cavity. As such, I have a query regarding a cavity physics related concept. At the bottom of page 2 it states the following:

With this system we naturally provide the three necessary ingredients for quantum synchronization: a controllable difference between the oscillation frequencies of two mesoscopic ensembles, a dissipative coupling generated by the emission of photons into the same cavity mode, and a driving force produced by optical pumping

I am particular interested in understanding what exactly is meant by "dissipative coupling generated by emission of photons into the same cavity mode". I'm having difficulty sourcing a basic description of this cavity process. Can anyone provide some insight into this or a good basic reference in literature? Thanks for your time and assistance.

 

[DrClaude]

Since the cavity is not perfect, it has a natural decay as photons can escape the cavity. Therefore, an excited atom also has a decay channel through its coupling to the cavity modes.