Speckle-free laser imaging

Many imaging applications require increasingly bright illumination sources, motivating the replacement of conventional thermal light sources with light emitting diodes (LEDs), superluminescent diodes (SLDs) and lasers. Despite their brightness, lasers and SLDs are poorly suited for full-field imaging applications because their high spatial coherence leads to coherent artifacts known as speckle that corrupt image formation. We recently demonstrated that random lasers can be engineered to provide low spatial coherence. Here, we exploit the low spatial coherence of specifically-designed random lasers to perform speckle-free full-field imaging in the setting of significant optical scattering. We quantitatively demonstrate that images generated with random laser illumination exhibit higher resolution than images generated with spatially coherent illumination. By providing intense laser illumination without the drawback of coherent artifacts, random lasers are well suited for a host of full-field imaging applications from full-field microscopy to digital light projector systems.Comment: 5 pages, 4 figure

Lasing threshold dependence on excitation pulse duration in ZnO tetrapods

The dependence of the stimulated emission from ZnO tetrapods on the excitation pulse duration was studied. In all cases, clear lasing modes with a width of 0.5-0.8 nm were observed. However, lasing thresholds were significantly different. The thresholds observed were 57 μJ/cm2, 840 μJ/cm2, and 4.2 mJ/cm2 for 250 fs, 120 ps, and 6 ns excitation pulses, respectively. The same trends (a decrease of lasing threshold with a decrease of pulse duration) are observed in samples with different tetrapod densities, although the differences become less pronounced in higher tetrapod density samples where lasing from multiple tetrapods can occur. © 2008 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

Three-dimensional visible-light capsule enclosing perfect supersized darkness via antiresolution

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