Polymers Improve Electro-Optics

Alan Elliott

Larry Dalton runs short treks into the future. It's a world of unlimited bandwidth, a place with steerable microwaves where aircraft and ships are all wired with fiber optic cable.

And Dalton is convinced that such a future isn't too distant. It will be riddled, the chemist says, with plastic polymeric materials that he has developed with research teams at the University of Southern California and the University of Washington. The materials allow chips to translate electrical into optical signals at rates of 100 GB/s: 10 times the current lithium niobate standard.

"This is not obscure scientific laboratory technology," Dalton said. "It's actually being prototyped, so it is just a matter of translating prototype devices into commercialization."

The material relies on organic molecular groups called chromophores, which possess distinct optical characteristics caused by mobile electrons interacting with light.

It can be laminated directly onto a semiconductor wafer, creating as much as 300 GHz of bandwidth from a 1-µm modulator. The kicker is that it all happens on less than 1 V of electricity.

Tailoring the chromophore/polymer combination to electro-optic applications was a 10-year process funded largely by grants from the National Science Foundation, the US Air Force and the Office of Naval Research. Dalton said the top 40 companies in the US are exploring the technology.

"The good news is that this is a fairly broad-ranging technology," he said. "It's sort of like a silicon diode -- you can configure it to do many, many different functions."

One obvious market is in enabling high-speed electro-optic modulators to send data and communications traffic via fiber optic channels. Other applications include phased-array radar that steers beams between ground-based antenna systems and communications satellites, and sensors able to detect land mines or to monitor home, shipboard and aircraft electrical systems.

The new era of electro-optic modulation won't begin overnight, although the polymeric modulators are already available commercially, Dalton noted. Production-level quantities may be available within two years.