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A group of researchers from Case Western Reserve University and its partners have demonstrated their ability to control the direction of a laser’s output beam by applying external voltage. It is a historic first among scientists who have been experimenting with what they call “random lasers” over the last 15 years or so. It certainly is a step forward for the already booming laser industry.

Although the research leader, Giuseppe Strangi, a professor and a Ohio Research Scholar in Surfaces of Advanced Materials at Case Western Reserve, believes there’s still a lot of work to do, but this is a clear first proof of a transistor random laser, where the laser emission can be routed and steered by applying an external voltage. Strangi, who led the research and his collaborators, recently outlined their findings in a paper published in the journal Nature Communications. The project, funded by the National Academy of Sciences of Finland, was aimed at overcoming certain physical limitations intrinsic to those second generations of lasers.

The history of laser technology has been fast-paced as the unique source of light has revolutionized virtually all areas of modern life, including telecommunications, biomedicine and measurement technology. But laser technology has also been hampered by significant shortcomings: Not only do users have to physically manipulate the device projecting the light to move a laser, but to function, they require a precise alignment of components, making them expensive to produce.

Those limitations could soon be eliminated: Strangi and his partners demonstrated a new way to both generate and manipulate random laser light, including at nanoscale. Eventually, this could lead to a medical procedure being conducted more accurately and less invasively or re-routing a fiber-optic communication line with the flip of a dial, Strangi said.

Conventional lasers consist of an optical cavity, or opening, in a given device. Inside that cavity is a photo-luminescent material which emits and amplifies light and a pair of mirrors. The mirrors force the photons, or light particles, to bounce back and forth at a specific frequency to produce the red beam we see emitting from the laser. But the real problem was, what if one wanted to miniaturize it and get rid of the mirrors and make a laser with no cavity and go down to the nanoscale? That was a problem in the real world and why the researchers could not go further until the turn of this century with random lasers.

So random lasers, which have been researched in earnest for about 15 years, differ from the original technology unveiled in 1960 mostly in that they don’t rely on that mirrored cavity. In random lasers, the photons emitted in many directions are instead wrangled by shining light into a liquid-crystal medium, guiding the resulting particles with that beam of light. Therefore, there is no need for the large, mirrored structure required in traditional applications.

The resulting wave—called a “soliton” by Strangi and the researchers—functions as a channel for the scattered photons to follow out, now in an orderly, concentrated path. One way to understand how this works: Envision a light-particle version of the “solitary waves” that surfers (and freshwater-bound fish) can ride when rivers and ocean tide collide in certain estuaries, Strangi said. Finally, the researches hit the liquid crystal with an electrical signal, which allows the user to “steer” the laser with a dial, as opposed to moving the entire structure. That’s the big development by this team.

That’s why it’s called the ‘transistor,’ because a weak signal (the soliton), controls a strong one—the laser output, according to Strangi said. Lasers and transistors have been the two leading technologies that have revolutionized the last century, and the team has discovered that they are both intertwined in the same physical system. The researchers believe their results will bring random lasers closer to practical applications in spectroscopy (used in physical and analytical chemistry as well as in astronomy and remote sensing), various forms of scanning and biomedical procedures.

Other researchers on the project includes, Sreekanth Perumbilavil, Raouf Barboza and Martti Kauranen, from the Tampere University of Technology in Tampere, Finland; Armando Piccardi, of the Non-Linear Optics and OptoElectronics Lab at the University Roma Tre in Rome; Gaetano Assanto, who co-ordinated the research at both the Finnish and Italian universities; and Oleksandr Buchnev, of the Optoelectronics Research Centre at the University of Southampton, U.K.