Highly efficient phase locking and extracavity coherent combination of two diode-pumped Nd:YAG laser beams

Intracavity phase locking and extracavity combination of the two emitted beams generated by a Nd:YAG laser longitudinally pumped by two fiber-coupled diode lasers are investigated. Phase locking is performed by a diffractive component located inside a confocal Fabry-Perot resonator. The coherent addition of the two synchronized beams in a single TEM(00) wave is made by a birefringent interferometer, with 96.8% energy yield. 610-mW output power was obtained in a single-lobed beam profile with 30.5% optical-to-optical conversion efficiency in the continuous-wave regime.