Prof. Ooi seeks new applications for photonic integrated circuits

Across the world, only three companies - one in Scotland, one in Singapore and one in California - have made photonic integrated circuits (PICs) for optoelectronic devices by using a new technique called quantum well intermixing.

Boon-Siew Ooi, associate professor of electrical and computer engineering, is proud to have been associated with each one.

Ooi, who joined the faculty in July, was a member of the research group in Scotland that pioneered quantum well intermixing, a technique that creates multiple-wavelength, multiple-channel PICs on a single chip.

"Quantum well intermixing can be used to integrate devices such as low-loss waveguides, optical splitters, lasers, semiconductor optical amplifiers, photodetectors and modulators onto a single chip," Ooi recently told a reporter at FiberSystems International, a widely circulated trade journal in photonics.

A native of Malaysia, Ooi earned his bachelor's degree and Ph.D. from the University of Glasgow in Scotland and spent two additional years there as a research fellow.

As a starting Ph.D. student at Glasgow, Ooi knew little of photonics, which was then an emerging field. He credits his interest and success in the field to advice he received from John H. Marsh, his thesis adviser and future research collaborator. Marsh sits on the board of governors of IEEE (the Institute of Electrical and Electronic Engineers) and runs Intense Photonics Ltd., one of the three companies making PICs with quantum well intermixing.

From 1996 to 2000, Ooi served as an assistant professor at Nanyang Technological University in Singapore, where he led a team of eight working on III-V photonic integration, and collaborated with researchers in Canada, Australia and the United Kingdom.

Four of Ooi's Ph.D. students at Nanyang went on to work with DenseLight Semiconductor, the second company making PICs with quantum well intermixing. Ooi has contributed a number of quantum well intermixing patents to DenseLight, helping the company make and sell broad-luminescent spectrum LEDs and other photonic integrated devices to optoelectronic firms all over the world.

In 2000, Ooi co-founded Phosistor Technologies in California's Silicon Valley. He served as Phosistor's vice president for technology, managing an $8-million budget and supervising 12 engineers.

In addition to his numerous patents and patent applications, Ooi has authored more than 70 papers, which have been published in Applied Physics Letters, IEEE's Photonic Technology Letters and Journal of Quantum Electronics, and other journals.

Until now, says Ooi, PICs have found application mainly in telecommunications. Ooi says his work will remain based on quantum well intermixing while his focus will shift to the development of integration process technology for sensor-based applications. For one of his first projects at Lehigh, Ooi wants to develop a new intermixing technique using quantum-dot structures that measure angstroms in width. He hopes to find uses for PICs in biosensors and biometrics, in which areas, Ooi says, optical and photonic devices are being developed that could be used to "diagnose" skin and tissue profiles to ensure that computers and even guns can be used only by those with screened and authorized fingerprints, that is, by their rightful owners.

Ooi's role in this endeavor will be to try to make a broader-band light source for biometric, gyroscope and optical coherent tomography (OCT) applications. A sensor becomes more sensitive as the luminescent linewidth becomes broader. Ooi, who once achieved the feat of fabricating 10 lasers with varying wavelengths on a single chip, is confident he can increase bandwidth by a few folds and thus improve a sensor's sensitivity.