Phase-Locked Dual Polarization Frequency Combs in Yb:YAG

Mode-locked lasers polarization states are typically fixed by gain dichroism in crystalline media. However, dual-polarization oscillation and pulse-to-pulse polarization control in bulk isotropic active media have attracted attention recently [1], [2]. Apart from using extra-cavity polarization devices, one can wonder whether an oscillator can generate directly adjustable polarization sequences. Here, we demonstrate how phase locking of two orthogonal polarization eigenstates can occur in a passively mode-locked Yb:YAG laser using two quarter-wave plates.