At the University of Maryland, researchers have successfully demonstrated the use of thin air as an optical fiber to continuously guide high-power laser beams over long distances. This breakthrough is significant as traditional optical fibers made of glass are not suitable for guiding high-power laser beams due to damage and scattering of laser energy. Additionally, glass fibers require physical support structures and must be laid down well in advance of signal transmission or collection.
The researchers used ultrashort laser pulses to create filaments of high-intensity light that heat the surrounding air molecules, forming a low-density heated air ring that acts as a refractive index structure for guiding light. As air is used as the fiber, it has the potential to guide very high average powers, and the air waveguide can be directed at the speed of light in any direction, making it ideal for detecting pollutants and radioactive sources over long distances. This new technology eliminates the limitations of traditional glass fibers and opens up new possibilities for high-power laser beam guiding and remote signal collection.
Researchers at the University of Maryland have developed a new method for continuously operating air waveguides that can guide high-power laser beams over long distances. Traditional glass fibers cannot handle extremely high-power laser beams, so this new technique of sculpting fiber optic waveguides in the air itself using ultrashort laser pulses is a significant breakthrough.
In a recent experiment, the researchers successfully generated 50-meter-long air waveguides that could guide megawatt average power laser beams using just one watt of average laser power. However, there was a cooling dissipation period of 30 milliseconds between pulses, which prevented continuous wave guiding.
In a new Memorandum in Optica, the researchers demonstrated that increasing the repetition rate of the waveguide-generating pulse to 1000 Hz can maintain a continuously operating air waveguide by heating and deepening it faster than the surrounding air can cool it. This allows for the guiding of an injected continuous wave laser beam, significantly improving the utility of air waveguides and increasing the maximum average laser power that can be transported.
The researchers believe that continuous air waveguiding over kilometer and longer ranges is easily achievable with existing laser technology and modest power levels. This breakthrough has significant implications for transmitting high-power continuous laser beams and detecting pollutants from miles away.