Analytically characterizing far field pattern of super-modes from external cavity phase locked diode array

Analytical studies have been made on multi-lobed far field patterns of super-modes (SMs) from a broad stripe laser diode array (LDA) phase locked with an external cavity. Irrespecting the order of an SM, the far field pattern of the SM is multi-lobed. The far field pattern of the highest super-mode (HSM) or the lowest super-mode (LSM) is composed of evenly-separated single lobes, and that of other SMs contains repeated pairs of lobes. It is difficult to distinguish the far field patterns of the HSM and the LSM unless the normal direction is accurately determined. Similar difficulty is also encountered when trying to discriminate the jth and (M−j + 1)th SMs of the LDA containing M emitters.