Making Lasers More Colorful

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Without the mirror, Canalias says, "you can have a very compact and nice setup, and you don't need to worry much about it."

The OPO provides fine tuning between different wavelengths of infrared light--differences of 5 to 10 nanometers should be easy to achieve--making it ideal to use in spectroscopy to identify different substances, she says. "Whatever wavelength you need, you can generate." The device maintains the same wavelength even if it heats up with use--something that traditional OPOs don't do so easily.

Franco Wong, a senior research scientist at MIT's Research Laboratory of Electronics, says that a mirrorless OPO would be very useful because it wouldn't need complicated adjustments. It might make for a portable spectrometer that could easily be carried onto public transportation to check for chemicals found in explosives. "It's almost self-aligning," he says. "You set things up, and it would just operate."

Yujie Ding, a professor of computer and electrical engineering at Lehigh University, has been working on mirrorless OPOs for years, and he says that Canalias and Pasiskevicius have confirmed experimentally a structure that he and his colleagues described 11 years ago. While he's happy to have his predictions validated, Ding is skeptical that the experimental results can translate into something practical. Right now, the researchers' device requires a large, high-power laser, he says. In order for the new OPO to work with smaller, lower-power lasers, the banded crystal would need to be more than 10 times longer than its current 0.4-millimeter length. But due to the properties of the crystal, it's difficult to make the bands uniform in a bigger piece of crystal, Ding says.

Canalias says that she has plans to try to make the crystal longer and at the same time decrease the width of the bands by at least half to gain even greater control over the quality of the output beam. She suspects that within the next 10 years this prototype could find its way into a practical commercial device.