Bubbles and "Champagne"

For a woman once accused of lacking the requisite "math gene," Julie Fouquet '80 has done pretty well. After graduation, she earned a doctorate in applied physics from Stanford, then took a research post at Hewlett-Packard. Over the years, her work there has included designing lasers and studying "time-resolved photolumin-escence of compound semiconductors." Last year, she unveiled a new invention: a patented all-optical switch. The tiny device is poised to unleash the long-awaited, full power of fiber-optic cables, and chase a market estimated at billions of dollars.

Julie Fouquet with her ground-breaking all-optical switch--the diamond-shaped object in the center of the circuit board where the cables meet.

Photograph by Glenn Matsumura

In the race for ever-greater bandwidth and faster Internet access, fiber-optic cables, when operated at full capacity, can carry huge amounts of data at virtually the speed of light. Fiber-optics are especially important in communicating "rich media": video, audio, interactive software, and high-resolution graphics. "They will change our lives in many ways," says Fouquet, who now works at one of Hewlett-Packard's spin-off companies, Agilent Technologies in Palo Alto. "You could have full-motion video on your home computer screen. Grandparents who live far away could enjoy watching their grandchildren grow."

Fiber-optic cables are already in use, of course, but their potential for creating an information "ultra-super highway" has not yet been fully realized. Problems arise when the light signals get backed up at the ca-bles' connectors--like bumper-to-bumper holiday traffic at the toll booth. The light- ray signals must be converted from optical (or photonic) to electrical impulses, and back again, to pass through to the next cable. That slows the network, risks losing data, and also requires massive amounts of unwieldy equipment, Fouquet notes.

The key question is how to enable the light signals to travel entirely as photons. "This was one of the biggest problems with fiber-optic cables," she says, "and our switch is solving that problem. It is a very important enabling technology."

The device, she explains, "is really very simple." Picture a diamond-shaped matrix the length of two dimes and nearly as thin, made of glass and silicon. Each switch has 1,024 crosspoints through which light is directed to microscopic trenches filled with a secret liquid. Most of the time the light travels straight--passing through the liquid in the trenches unimpeded, and on to Timbuktu. If a shift is required, a bubble forms in the trench and the light is reflected off the interface between the glass walls and the bubble in a new direction, she says. The connection takes less than five milliseconds, and the switch can make up to 32 transfers at once, making it especially useful in metropolitan communications markets.

"Uncomplicated" is a good way to describe Fouquet. When explaining the switch, she rattles off components more like a neighbor sharing a recipe for meatloaf, than like a groundbreaking optical-communications scientist. Outside the lab, she has a husband, two sons, a house they took years to remodel, and a vacation home on the northern California coast.

In high school, she was called "brain"--much to her embarrassment. Teachers asked her to help other children with homework, and there is a family story of a very young Fouquet calculating the number of cups available for a party. "My mother says I was interested in numbers from before I can even remember," she says. As a teenager, she liked math and earth science, and was one of only a few girls at her school to take a college-level calculus class. A girlfriend whose father was a successful electrical engineer prompted her to stay on for a second year: "She saw no reason not to excel, and persuaded me to keep her company," Fouquet remembers. "It was a good thing, because I challenged myself."

At Harvard, she discovered a love of light. "My laser lab sophomore year was great fun; we made holograms," says the Dunster House alumna. So was measuring astronomical masers around stars and using the big telescopes at the Smithsonian Astrophysical Observatory. In an electrical-engineering class, she built "a little optical communications link" using a junky old amplifier. "I sent a message out over it, but then suddenly it burned up from all the old padding and dust inside and smoke started coming out," she laughs. "It worked. But it didn't work for very long."

She was one of three women in her class to concentrate in physics, and one of two to work in the field after graduation. She remembers one particularly unenlightened professor, but is quick to say that her adviser, the late Gade University Professor Edward M. Purcell, among others, was very supportive. At Stanford, she was surprised to find some of her peers particularly close-minded. "I hit a bunch of students who didn't seem to like the idea of a woman there. When I was assigned a seat in my office, there were comments like 'Oh good, now we have a secretary,'" she says. "Some guys tried to convince me to drop out because I didn't have the 'math gene.'" In fact, her scores on quantum-mechanics problems more than once topped theirs. Since then, Fouquet has worked in various ways to encourage girls and women to enter science. She ran the Women in Science and Engineering Lecture Series at Stanford, and has subsequently mentored women and hired female graduate students. But even at Agilent, there are not that many female researchers, she says. "From what I see, the number of women in the sciences is still not improving too much over time."

Being a woman, in fact, has nothing to do with her actual work, and nothing to do with her first major career decision: to choose laboratory-based laser research over astrophysics. "I am an experimentalist, more than a theorist: I like to twiddle knobs," she explains. "When you study astrophysics, things happen far, far away and there is nothing you can do to change that. It's not like when you work in a lab--where you can control the laser. This field also has many more commercial applications, which appealed to me."

In 1995, Hewlett-Packard asked Fouquet to look into making an all-optical switch. Dozens of companies, she says, are also trying to build such a switch; Agere Systems, for example, has a competing device. Most of these firms, including Agere, are using micromirrors on silicon chips to redirect the light, or liquid crystal technology (molecules that flow like liquid and can manipulate properties of light). Fouquet investigated these options, and found them lacking--or just too complex. For starters, directing the mirrors is a difficult, mechanical problem. "It's like trying to aim a laser at a person who is running six miles ahead of you while you're in a truck that is bouncing around on the road," she says. There was no existing technology that could change and block light as well and as fast as it should be done, she continues, "so it was either give up or develop something new."

In the end, Fouquet was inspired by methods that could not have been closer to Hewlett-Packard's core: thermal ink-jet printers. Considered one of the clumsier technologies around, the printers make the ink boil, a bubble forms, and the ink is forced to the tip of a pen, where it shoots (or "jets") onto the paper. "The bubble shoves the ink out of the orifice. It's all very fast and explosive," she says. "We don't do things as fast, but we use similar actuators" to heat the liquid and form bubbles in the switch's trenches. "We had a lot of the ideas and intellectual property in-house," she notes, "and we took advantage of that."

Using partially constructed inkjet pens, she began to experiment. In the switch, the bubble is critical to reflecting the light onto a new path; when it forms, the bubble displaces the fluid from the trench, which makes the space more like air. "It is the interface between the glass and the bubble that shifts the light," Fouquet reports. The physics principle at play is called "total internal reflection." Think of a still swimming pool on a sunny day, she says. "If you're in the pool, under the water, and if you look straight up, you can see the sky. But if you try and look at someone standing by the side of the pool, you might not see that person at all. This happens when you're in a dense medium trying to look into a less dense medium, like air."

One of the biggest challenges turned out to be controlling the bubbles themselves--thus, the effervescent technology was dubbed "champagne" in the lab. Looking to this silly-sounding idea to solve an optical problem was so unorthodox, she recounts, that early on, "the lab director had a meeting in which he told everyone to throw tomatoes at me--'Is this really going to work? This idea sounds so crazy.' The result of that meeting was 'This idea is worth a try.'"

Within a year, demonstrations of the new "champagne" succeeded; last March Agilent publicly introduced the product. The switch is now being used by Alcatel, the giant French communications equipment company, and other customers, Fouquet says--"We are selling everything we can make." She now spends much of her time "on manufacturing the switch and getting it out the door. People want to make money off the technology, and I like to make sure that something real comes out of all this thinking and experimenting. It's exciting."

Of course, Fouquet has also begun to work on new projects. "It has to do with optical switching," she says discreetly. "Let's just say it's more research."