Lateral far-field interference pattern of buried heterostructure lasers

Subpeaks in the lateral far-field pattern of buried-heterostructure InGaAsP/InP lasers are shown to be caused by the interference between light scattered at the lateral sidewalls out of the active region and the guided main beam. This is made clear by discriminating the scattered light and the main beam utilizing a screen at the facet. It is demonstrated that the main beam remains to be a fundamental mode and the scattered light intensity is usually 30% or less of the main beam intensity, even for a diode that exhibits a highly complicated far-field pattern.