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Alkim Akyurtlu Pushes Research Boundaries

Metamaterials Show Novel Properties 

Alkim Akyurtlu

05/10/2006
By For more information, contact media@uml.edu or 978-934-3224

Dr. Alkim Akyurtlu is interested in research that touches the far boundaries of what’s knowable. And then she likes to incorporate that knowledge into her courses.

Research and teaching comprise the academic lifeߞ;a combination that Akyurtlu, assistant professor of electrical and computer engineering, finds especially rewarding, even in comparison to her previous work at MIT Lincoln Labs. UMass Lowell also offers many opportunities for collaborative research, leading her in new directions.

“My main expertise is in computational electromagnetics,” says Akyurtlu. “I’m more theoretical and (in my collaborations) I’m becoming involved in the experimental aspect of the research, which forces me to face the ‘real world’ challenges. It’s fun to go beyond theory to see if what we’ve predicted will happen.”

Akyurtlu is putting theory and experiment together in exploring materials that don’t exist in natureߞ;metamaterialsߞ;to understand and demonstrate their novel properties. Metamaterials invert the two fundamental properties of material, namely the permittivity (electrical response) and permeability (magnetic response). These properties are simultaneously negative and therefore show a negative index of refraction, so materials with these properties are commonly named negative index metamaterials, or NIMs.

In explaining the fascination of NIMs, Akyurtlu says, “Water exists in nature and has certain properties with which we’re familiar. Put a stick in a glass of water and the light refracts, the stick appears to bend in predictable ways. Put NIMs instead of water into a glass and a stick will appear to bend in the opposite direction.” These materials not only result in the reversal of Snell’s Law (on light refraction) but also of the Doppler Effect, which can lead to interesting military applications. 

Most exciting, conceivably one could construct a perfect lens in which a mere slab of material can focus light.

“A perfect lens can produce a sub-wavelength image,” says Akyurtlu. “It provides the possibility for high-resolution lenses that can resolve details finer than the wavelength of light. But no one has yet demonstrated a perfect lens.”

Metamaterials consist of conducting resonance structures that are embedded in or deposited on a non-conducting substrate; the size and configuration of the inclusions determines the frequency of transmission. When the largest size of the inclusions and their period is less than the wavelength of light, the material appears as a bulk medium.

Akyurtlu is working on two research projects funded by the Air Force Office of Scientific Research. The first involves improving antennas through integration of metamaterials within the antenna itself; rather than having a wire and separate electronics, the antenna itself acts as a filter. The research uses inclusions in the microwave range to increase the bandwidth and miniaturize the antenna size. These “patch” antennas are compact and often used in automobile and space applications. The mathematical theory of antennas is complex and Akyurtlu teaches a course in the subject, as well as courses in radar systems and engineering math.

The second Air Force-funded project is to develop NIMs in the area of visible light, something that has never been done. Akyurtlu and her team have developed a novel structure using nanoscale-size spherical inclusions, but the key issue is to prove the concept.

“The measurement of phase change is very difficult,” says Akyurtlu, who is working with Physics Profs. William Goodhue and Aram Karakashian on building a test bed for characterization of metamaterials. “Moreover, the equipment is very expensive: One piece I was looking into buying is around $100,000.”

Testing is critical: “The test bed is part of the proof,” she says. “We would be the first to show NIM effects in the visible regime.”

Akyurtlu supervises five doctoral candidates, two of whom will graduate this summer. She is married, lives in Arlington and has a 15-month-old daughter, whom she describes as “my inspiration!”