Arrays of nanopillars can act as efficient lasers; however, one of the obstacles for the use of such structures is that they radiate energy into a doughnut-like pattern. By breaking the periodicity of the structures into a superlattice arrangement, researchers from the USA were able to reshape the radiation pattern so that almost all energy was radiated into the direction normal to the interface. Authors fabricated a periodic array of nanowires with a square unit cell arrangement, as well as their proposed quasi-aperiodic structure, with each unit cell containing four nanopillars placed asymmetrically. Each nanopillar has quantum wells built in, and the photoluminescence measurements have shown that indeed the radiation pattern of the quasi-aperiodic structure is normal to the interface. At the same time, the radiation has become more broadband as compared to the results for the original periodic structure. Authors support their findings by numerical calculations of the band-gap diagrams of the structures.
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