Lasers are double-edged swords when used as illumination sources in projection devices. They offer a superior brightness and a reduced maintenance compared with other sources. However, the image quality they enable is limited by intensity inhomogeneities resulting from speckle. Speckle is an interferential effect suffered by the light scattered at the screen surface. It becomes particularly visible when using highly coherent sources such as lasers. Current solutions to mitigate speckle in laser-based projection consist in using multiple sources or bulky and moving correction optics. Here, Ke Guo and co-workers show a path toward speckle-free projection with a single and miniaturized laser platform. They design plasmonic lasers consisting of a ~ 90 × 90 μm densely packed assembly of square patches. Each patch consists of a square array of silver nano-cylinders covered with a light-emitting material. Upon building the laser from ~ 20 × 20 μm patches with slightly different array pitches, multi-mode lasing is obtained. The lasing signal presents a good directionality and a lowered coherence that is promising for projection with mitigated speckle effects.
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