Control of the output power of a laser with an active unstable resonator

The approximation of the steady-state phase method is used to describe field formation in an unstable resonator with active mirrors and to derive expressions for the resonator transmission and the phase of the output radiation. An algorithm is suggested for active control of the unstable resonator losses. A comparison between the results of the numerical modeling and estimates using the steady-state phase approximation confirmed that the model is satisfactory. It was found that the proposed algorithm can be used to control the output power of a laser with an active unstable resonator in a wide range of parameters whilst the angular distribution of the output radiation is maintained close to the diffraction limit.