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Research Highlight

Laser speckle analysis resolves mesoscale transitions

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In the experiment to collect speckle patterns depicted in this diagram, polarized laser light is focused onto a sample and reflected from the VO2 surface. Green and blue represent regions of different dielectric values. The reflected speckle pattern is sampled using a standard detector. The image gives an example of a typical speckle pattern. This technique only requires simple and widely available equipment.
An elegant experimental approach, which requires only simple and widely available equipment,  provides previously inaccessible spatial and temporal resolution on coexisting electronic domains in a technologically promising transition-metal oxide.

Self-organization of mesoscopic domains that arise from underlying microscopic interactions is ubiquitous in condensed matter physics and is tied to some of the most intriguing yet least understood phenomena, i.e. high-temperature superconductivity, colossal magnetoresistance, and metal–insulator transitions. Thus, understanding the configuration and evolution of these domains is a critical step toward creating novel functionality for next-generation devices.

Laser speckle intensity statistics arising from self-organized mesoscopic domain configurations can signal the onset of resistive switching well before the phase transition can be observed macroscopically. The probing laser can be wavelength-selected to isolate a range of domain sizes near the transition temperature. An analysis of speckle statistics can be performed in real time and offers a straightforward method to investigate dynamics at time scales orders of magnitude faster than state-of-the-art scanning probe techniques.  

 

K. Seal, A. Sharoni, J. M. Messman, B. S. Lokitz, R. W. Shaw, I. K. Schuller, P. C. Snijders, and T. Z. Ward, “Resolving transitions in the mesoscale domain configuration in VO2 using laser speckle pattern analysis,” Scientific Reports 4, 6259 (2014).

 

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