Abstract
Due to thermally induced birefringence effects, axisymmetrical TEM01* modes with four intensity peak points are observed in the critical stable working regions of a diode-side-pumped neodymium-doped yttrium aluminum garnet (Nd:YAG) laser resonator in continuous-wave operation. Then, because of the use of a Cr4+:YAG saturable absorber, four phase-locked Gaussian beams are formed symmetrically in the resonator, and high-contrast interference fringes with a sine–cosine modulated Gaussian profile are observed in the far field due to coherent addition of the four beams. The phase locking effect is robust and stable passive Q-switched pulses are obtained simultaneously.