Abstract

Y-junction laser arrays, grown by metal-organic chemical vapor deposition, have been shown to couple effectively the adjacent emitters inphase. The inphase radiation pattern emits symmetrical to the normal of the cleaved facet, and the number of radiating lobes is determined by the emitter width and separation. The index guided arrays of emitters have been fabricated using both buried heterostructure waveguides and inverted channeled substrate planar waveguides. These guiding structures minimize the evanescent coupling between the guides, which would normally tend to enhance the out-of-phase radiation mode. Stable far-field patterns characteristic of the inphase mode were observed up to 400 mW. In this case the radiation pattern contained three lobes. By flaring the waveguides prior to the facet the near-field fill factor was increased to >80% resulting in near-single-lobe emission. Theoretical analysis of the Y-junction array indicates that the lowest-order spatial mode is dominant and that the near-field radiation pattern is nearly uniform with only the outermost stripes decreased in intensity by ½. The uniform near field uses the injected charges more efficiently than an evanescently coupled array. Thus the modal discrimination is greater even at the higher-power levels.

© 1987 Optical Society of America