Phase-coherent addition of laser beams with identical spectral properties

We coherently add two beams from separate diode lasers with identical frequencies to obtain a single coherent beam (degree of coherence equal/similar 1) with well-defined polarization. The frequencies of the two sources are simultaneously injection locked to a third laser oscillator. The laser beams are merged at a polarizing beam splitter cube with an active stabilization of the relative phase against acoustic noise and thermal drifts. Different schemes to control the relative phase are investigated. The system can easily be extended to coherently add a large number of laser sources