Method for Using Air Like Optical Fiber Developed
24 July 2014
A method for making air behave like optical fiber, sending signals over short distances, has been developed by the University of Maryland and published in Optica. In their experiment, the researchers used the so-called "air waveguides," over about 1 meter (3 feet), that served to enhance the light signal. Those waveguides were 10 Hz Ti:sapphire laser pulses at 800 nanometers fired with pulse widths between 50 and 100 femtoseconds at a power of 16 millijoules. The signal passing through the waveguides was 50% stronger compared to the one that didn't.
Researchers compared the way the system worked to the light pulse actually carrying its own lens through the air - the laser increases its reflective index at the center of the beam, making the pulse collapse into filaments. As had been demonstrated in prior experiments, such filaments of air also heat up as the beam passes through, causing the air to expand.
This leaves a hole of low density behind with a lower reflective index than the air around it; this was further broken down by the laser in the new experiment, which also created a spark. Light from that spark was conducted to a detector a meter away from the waveguide, with a strong enough reflected signal for scientists to analyze the air's chemical composition.
Using waveguides over longer distances - at least 50 meters (164 feet) - is the next big breakthrough the research team is hoping to achieve. If they are successful, the method could be used for a wide variety of purposes, from studying the chemical composition of the upper atmosphere or detecting air pollution, to long-range communications and the development of high-resolution topographical maps.