Professorship aids Knezevic’s quantum mechanics research

// Electrical & Computer Engineering

Tags: ECE, Knezevic, quantum mechanics, Splinter professorship

Photo of Irena Knezevic
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Smartphones, smartwatches, laptops, Fitbits—all consumer electronics rely on the physics of things you cannot see.

And Irena Knezevic, a professor of electrical and computer engineering at the University of Wisconsin-Madison, seeks to better understand this nanoscale physics to improve our lives.

She recently received the Patricia and Michael Splinter Professorship in Electrical and Computer Engineering to support her in that endeavor.

The Splinter professorship, created by electrical and computer engineering alumnus Michael Splinter (BS ’72, MS ’74) and his wife Patricia, supports Knezevic as she studies quantum mechanics, the physics of things at atomic and subatomic scales. Specifically, she works to understand how charge, light and heat interact in nanoscale systems. To do so, she makes mathematical models to explain the physics in these systems and writes computer code to solve the models. “Quantum mechanics is the physics of things you can’t see,” says Knezevic. “And the best way to deal with the things you can’t see is with math.”

Knezevic focuses on the behavior of electrons. What makes small objects like electrons differ from large objects is that they behave more like waves than like particles. Knezevic works to understand what happens when you confine the dynamic wavelike behavior of electrons to nanoscale dimensions.

One area of her research focuses on quantum cascade lasers, which can emit more energy in the form of light than more standard lasers. Knezevic simulates the physics of these devices and shares her findings with collaborators who then apply her work to build improved quantum cascade lasers that eventually can be used in imaging, telecommunications, trace gas analysis—anything with a sensor that has a light emitter.

Worldwide, few researchers are doing similar microscopic quantum cascade laser modelling. Although some other groups are researching the lasers, what sets Knezevic’s work apart is that her models are multiscale and multiphysics models. Multiscale means she studies the lasers from the atomic level of photon and electron behavior all the way up to the micron level of the whole laser; multiphysics means she investigates the interplay between charge, light and heat within the entire system. Since other groups studying quantum cascade lasers often look primarily at electron transport, Knezevic’s holistic inquiry is state-of-the-art.

While quantum cascade lasers are practical devices, Knezevic also studies nanomaterials such as graphene and carbon nanotubes. Graphene, a nanomaterial comprising a single layer of carbon atoms. This thinness makes graphene behave differently on different surfaces. “One of the coolest things about graphene is understanding how it behaves when you put it on different materials,” says Knezevic.

When you take graphene and roll it up like cannoli, you create a carbon nanotube. Knezevic studies how carbon nanotubes capture light energy by temporarily binding it into ephemeral particles known as excitons. She explores the physics of excitons in disordered nanotube systems to better understand how light energy moves from nanotube to nanotube on the way from where it was absorbed to where it is being collected. Currently, carbon nanotube films are an inexpensive way to harvest solar energy, but they are also inefficient. Knezevic hopes that her research will lead to more efficient solar cells that can be implemented on a global scale.

In addition to these ongoing research projects, the Splinter professorship provides Knezevic with support to venture into new research areas, like nanoscale antennas. Nanoscale antennas are just like typical radio antennas, but much smaller. This makes them behave unexpectedly. “When you make antennas small, there is physics that arises that wasn’t there when the antenna was bigger,” says Knezevic.

By marrying her knowledge of light emission at the nanoscale with her knowledge of quantum transport, Knezevic aims to better understand the physics of nanoscale antennas. This research will help to shape the future of telecommunications and sensing.

To assist with Knezevic’s diverse research, the Splinter professorship also allows her to fund a graduate research assistant and share her passion for the beauty of quantum mechanics. And, at the end of the day, she aims to share that passion not only with her students, but with us all. “Beautiful math and physics underlie all of engineering,” says Knezevic.

Author: Pat DeFlorin