Radiation characteristics analysis of broad area laser diodes and the proposal of improvement methods

Abstract

SUMMARYIn a broad-area laser diode (LD) having a wide stripe width, a Gaussian pattern is not obtained in the near field (NFP) and the far field pattern (FFP) has multiple peaks, which is known as filamentation. Thus, when used in communications, the losses in the side lobes are large, and antenna directivity problems develop. In this paper, we solve the wave motion equation and the dispersion equation to explain the radiation characteristics during filamentation. In particular, we explain the relationship between the phase distribution at the LD facets and the NFP and FFP. We also investigate the improvements in the radiation characteristics by examining the phase distribution at the facets and the injected current distribution in the direction perpendicular to the wave propagation direction. The results showed that the FFP can be a single peak with a side lobe suppression ratio of 13.4 dB when phase correction having two peaks was performed at the facets. The results also showed effective narrowing of the current distribution.