What happens when physicists decide their lab is too small? Someone starts shooting powerful lasers down the corridor in the middle of the night.
This wasn’t just a bunch of students playing laser skirmish when they were bored.
The American researchers had been investigating “optical guiding”: a method of guiding light through air, which could be used for long-distance laser communication.
They had shown that this works over distances of less than a meter, but they couldn’t extend the range because their lab was too small and the extremely powerful laser they used couldn’t be easily moved.
Their solution? Make a hole in the wall and shoot the laser into the 50 meter long corridor.
“There were big challenges: the huge scale up to 50 meters forced us to rethink the fundamental physics of air waveguide generation, plus the desire to send a high-power laser down a 50-meter public corridor naturally raises big safety concerns,” says Professor Howard Milchberg , a physicist at the University of Maryland, USA.
“Fortunately, we had excellent cooperation from both the physics (department) and from the Maryland Environmental Safety Office!”
This is important, because the laser is powerful enough to burn paper and skin.
The researchers did their work at night so they could block off the corridor with minimal inconvenience to their fellow residents.
“It was a really unique experience,” says Andrew Goffin, an electrical and computer engineering student at the University of Maryland.
“There’s a lot of work that goes into shooting lasers outside the lab that you don’t have to deal with when you’re in the lab – like putting up curtains for eye safety. It was definitely tiring.”
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After several nights of testing, the researchers found that their waveguide technique could preserve about 20% of the light that would normally be scattered through the air. With more testing, they believe they can make the guide more effective.
“If we had a longer corridor, our results show that we could have tuned the laser for a longer waveguide,” says physics graduate student Andrew Tartaro.
“Based on new lasers we’re getting soon, we have the recipe to extend our guides to one kilometer and beyond,” says Milchberg.
A paper describing their experiment has been accepted by Physical examination X.