Quasi-instantaneous (<20ps) phase locking in single-lobe y-coupled laser diode arrays

The time evolution of the far-field radiation pattern of an in-phase locked Y-coupled diode laser array has been observed with a streak camera. A strong central lobe 2.3° wide with faint secondary sidelobes separated by 15° forms in a time less than 20 ps. This indicates that the elements of the array are instantaneously locked in-phase.