November 17, 2003

Two Scientists Named Best Inventors of 2003 by 'R&D Magazine'

Two researchers at the University of Rochester have received this year's R&D100 Award, which honors the most innovative inventions of the year and is often called "the Nobel Prize for technology." The contest, sponsored by R&D Magazine, recognized the work of Roman Sobolewski, professor of electrical and computer engineering, and David Williams, professor of brain and cognitive sciences. Coincidentally, both pieces of down-to-Earth technology began life as advancements in astronomy.

Sobolewski created the superconducting single photon detector--an extremely sensitive and accurate infrared detector that can ferret out a misfiring transistor from the billions on today's Pentium and PowerPC chips. The new device can detect single photons, making it sensitive enough to meet the demands of new chip makers who need to test billions of transistors on each chip as quickly and efficiently as possible. The key is to exploit a quirk of physics; when transistors switch, they sometimes emit a very brief flash of infrared light. This flash can reveal much about how the transistor is behaving--but only if a detector catches it. Conventional semiconductor detectors either can't see in the infrared or can't see such brief flashes, or they report flashes when there aren't any.

The breakthrough for Sobolewski came in a meeting with Russian astronomers.

"We were working on the photoresponse of superconductors and we contacted this group at Moscow State Pedagogical University that was using superconductors for radio astronomy," says Sobolewski. "The upper radio bands are essentially far infrared bands, so we got together with the Moscow team and worked on putting their materials into our detector."

With the Russian astronomy group, led by physics professor Grigory Gol'tsman, the team showed that ultrathin strips of a metallic compound called niobium nitrite a millionth of a meter wide and only several atoms thick could detect single visible and infrared photons. Inside a kind of thermos of liquid helium at temperatures near absolute zero, the strips, fabricated in Moscow, become a superconductor and are able to conduct electricity without any of the resistance found in normal conductors like copper wires. This lack of resistance is essential because it makes the superconductor like a calm pond--toss in the smallest stone and you'll notice the ripples. A single photon of infrared light plunking into the material could be detected, unlike the case with conventional types of detectors that are full of noise, like a storm on the pond obscuring all but the largest perturbations.

Such precision is crucial because when a clock pulse passes through a chip and the transistors emit just a photon or two of infrared light, most conventional semiconductor single-photon detectors will miss the flash or misinterpret their own stormy perturbations as an incoming photon. The flash can divulge quite a bit about the way a chip is working; for instance, whether or not the transistor is switching at the correct time, a vital consideration for today's incredibly high-speed chips.

Williams' work also hails from astronomical research. Adapting technology originally developed by astronomers to obtain better images of the heavens, Williams developed an optical system that has given research subjects an unprecedented quality of eyesight. The research dramatically improves the sight even of people who have 20/20 vision.

The technology is known as adaptive optics, originally developed by astronomers to sharpen images from telescopes by correcting for aberrations in the atmosphere. Williams, who is Allyn Professor of Medical Optics and director of the University's Center for Visual Science, has led a decade-long effort to apply the technology to improve ordinary human vision.

The system based on Williams' research is called MEMS-based Adaptive Optics Phoropter (MAOP) and it allows doctors to treat patients with visual aberrations that were difficult to measure and correct in the past.

His researchers direct a harmless, highly focused spot of light into the eye of a research subject and measure the light that is reflected outward. That light provides a glimpse or snapshot of the topography of the eye in exquisite detail. The light is broken up into 217 laser beams that are sent into a sophisticated device known as a wavefront sensor. The sensor analyzes deviations in each beam's path, revealing tiny imperfections or aberrations that exist in the person's cornea and lens.

These precise measurements are sent to a sensitive "deformable" mirror--a mirror that can bend and customize its shape according to the measurements of a person's eye. Such flexible mirrors form the heart of traditional adaptive-optics systems used in astronomy. The mirror in Williams' laboratory is a two-inch-wide device that bends as little as one or two micrometers (just one-fiftieth the width of a human hair) thanks to 37 tiny computer-controlled pistons. This subtle shaping, done in response to the customized measurements of a person's optical system, alters the light in such a way that it exactly counters the specific distortions in a person's eye.

MAOP also enables clinicians to more successfully detect, diagnose, and treat retinal diseases, such as retinitis pigmentosa, glaucoma, diabetic retinopathy, and macular degeneration.

The MAOP was developed in a collaboration led by the Lawrence Livermore National Laboratory and included the University of Rochester, Bausch & Lomb, Boston Micromachines Corp., Sandia National Laboratories, and Wavefront Sciences. Sponsorship for the MAOP comes from the multi-institutional Center for Adaptive Optics. Underlying technology for the MAOP is available for license.