Controlling chaos
Using the absorption line of ethylene gas as a frequency-to-amplitude converter, the scientists could measure even the slightest change in frequency as a change in amplitude. Once they could identify and measure chaos, they could also control it.
In what Chin calls a very simple technique, dubbed occasional proportional feedback, the team applied a correcting pulse to the laser current, decreasing the frequency excursions and making the laser line sharper and more useful.
"A whole range of applications is opening up because of chaos control," he said. "Because we are already using these lasers for spectroscopic work, and the application seems to be simple, we can use this technique in applications immediately."
The team also plans to use the newly tamed laser as a local oscillator, which coherent optical systems employ to generate a composite wave that results in greater receiver sensitivity.
Further testing of this chaos-control method will take place in April at a similar facility at the University of Cologne in Germany. The researchers also believe that optically pumped lasers would be ideal candidates for this technique because the frequency time scale on such lasers is slower, making chaos easier to identify and control.