Applied Physics

Reading Speckle Patterns

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Science  17 Jan 2014:
Vol. 343, Issue 6168, pp. 231
DOI: 10.1126/science.343.6168.231-b

Intensity and pinpoint focus over long distances are probably the most familiar features of laser light. It is the spatial and temporal coherence of the light, with the photons in the laser beam marching in lockstep, that lends itself to the above features but also provides the most valuable properties for the vast applications in communication and imaging. When a laser beam hits a random medium, such as a wall or sheet of paper, the coherence of the photons results in the formation of a speckle pattern. This pattern is determined by the properties of the propagating light and the diffusing medium. Using a thin layer of alumina particles as a highly scattering medium, Mazilu et al. show that they can “read” the generated speckle pattern, and by modeling it with a number of principal components describing the propagating light beam can determine the wavelength of the light with high resolution. Because the speckle pattern is dependent on a number of parameters that can be encoded onto the propagating laser light, the relative simplicity of the technique may find application in areas such as lab-on-chip spectroscopy or security features in bank notes or sensitive documents.

Opt. Lett. 39, 96 (2014).

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