Working of 'random' Lasers Explained

Scientists have explained in a new research how random lasers occur.

Scientists have explained in a new research how "random lasers" occur. A decade ago, University of Utah scientists had discovered a new kind of laser that was generated by an electrically conducting plastic or polymer, no one could explain how it worked and some doubted it was real.

Now, the Utah researchers have found that these "random lasers" occur because of natural, mirror-like cavities in the polymers, and they say such lasers may prove useful for diagnosing cancer.

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"Nobody knew how it worked until now," said Z. Valy Vardeny, a distinguished professor of physics and senior author of the new study.

"We succeeded in imaging the cavities. This is a big step in our understanding of this bizarre phenomenon, which not many people believed," he added.

In the new study, Vardeny and colleagues created images to reveal the natural cavities within a "pi-conjugated polymer film," which is a thin film of an organic polymer - named DOO-PPV - that conducts electricity even though it is a plastic-like material.

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The microscopic cavities - natural irregularities within the plastic - act together like the mirrors in regular resonators that help amplify the light in a conventional laser.

Lasers "are carefully designed and constructed to produce laser emission," said study coauthor Randy Polson, a senior optical engineer at the University of Utah's Dixon Laser Institute.

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"Surprisingly, there is a class of lasers where laser emission happens from materials that are literally shaken together," he said.

"These are called random lasers since the emission happens from an uncontrolled configuration - a disordered rather than crystal structure within the "lasing medium" - the material used to generate the laser," he added.

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"There has been some disagreement how random lasers operate. For an analogy, imagine you are outside a sports stadium and hear the roar of the crowd. Is the noise initiated throughout the stadium at the same time, or are people yelling on their own?" he pondered.

"Our work has shown that the emission from random lasers happens with one emitter at a time, like individuals in the crowd yelling unconnected shouts," Polson said.

Vardeny and his colleagues now are conducting more research aimed at developing and commercializing random lasers to distinguish cancerous from noncancerous human tissue.

Source-ANI
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