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Researchers at Penn State have found a way to use ultrasonic and acoustic guided waves to alter how light bounces off of objects, a phenomenon called optical reflection. Image: iStock/@Meindert van der Haven

By Tessa M. Pick

From navigating ships and submarines using sonar to imaging organs in the human body using ultrasound technology, scientists and engineers have studied the numerous applications of sound waves for decades. Now, researchers at Penn State have found a way to use ultrasonic and acoustic guided waves to alter how light bounces off of objects, a phenomenon called optical reflection. Their technology received a patent on Feb. 2. 

Inventors Joseph Rose, Paul Morrow Professor Emeritus in Engineering Design and Manufacturing, and Akhlesh Lakhtakia, Evan Pugh University Professor and Charles Godfrey Binder Professor of Engineering Science and Mechanics, have been colleagues and friends for more than 30 years. This relationship — along with Rose’s expertise in ultrasonics and acoustics and Lakhtakia’s expertise in the field of optics — made the logistics for this patented technology come together naturally, according to the researchers.

“We have been friends for years, and we have always talked technically,” Rose said. “All of a sudden, we got this idea. We already know that ultrasonic waves can alter the flight of optical waves — it can bend waves, etc. — so we realized we could use this to alter optical reflection. We could combine our expertise to create this technology.” 

When light reflects off of a smooth or corrugated surface, the reflection, although less intense than the original light, bounces symmetrically directly from the point of contact with the surface. This may cause problems in some applications. For example, in fiberoptics, reflections can cause back-scattering noise, creating instabilities in optical communication networks. This reflection can also cause a “blinded” effect on microscope and tomograph images, obscuring important details.

To control these reflections, the researchers found they could apply sound waves to a system that splits and diffracts light to control the direction of the reflection. The system consists of conductors arranged on a glass plate, onto which researchers can launch controlled sound waves to change how the light diffracts, achieving an asymmetric reflection.

“Before we achieved the advances in modern technology, solutions were need-driven,” Rose said. “There would be a certain problem, and an engineer would try to solve that problem. Today, research is technology-driven, and that’s why we have made tremendous advances as engineers. We don’t know all the applications that might occur from our invention at this point, but it’s a physical concept that we feel will work well.”

Rose and Lakhtakia plan to apply for funding to further explore their technology and its potential applications. 

“This is the kind of research that comes out of the question, ‘What if?’” Lakhtakia said. “This research is curiosity-driven. We now know the capabilities of this technology, so now we will start to find what we can apply it to.”

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