Theoretical physicist Greg Gbur shares a slice of his life -- as nano-optics researcher, teacher, science writer and skydiver.
It’s Monday morning, and Greg Gbur (pronounced “ga-burr”) likes to start off his week by hitting the ice. Skating warm-up rounds in the over-chilled air of the ice rink just south of Charlotte, N.C., he tries to focus his mind. At any given time his thoughts may be fragmented on a number of subjects, ranging from the weekend's skydives, his current research on nano-optics, the blog post he is working on for his popular science blog, or even one of his seven cats. This morning he prepares for his figure-skating session with his coach. Afterward, he will go to work as a theoretical physicist.
Although his interests seem varied, even random, they all share something in common in Gbur’s restless mind — they are all areas that challenge him and give him goals for the next level of achievement and personal growth.
By profession, Gbur is an assistant professor in the Department of Physics and Optical Science at UNC Charlotte. His work in the field of nano-optics is difficult for the layperson to understand, but Gbur explains it clearly, in a way that makes him popular in the classroom. He is one of those people who can make a subject perfectly understandable in the moment. It is not until you are trying to share his explanation later with a friend that you realize you only absorbed about one quarter of what he told you.
Nano Means Very, Very Tiny
Gbur’s focus, nano-optics, may be loosely defined as the study of light interactions with structures much smaller than the wavelength of light. Visible light has a wavelength on the order of 500 nanometers, or 0.0000005 meters. Nano-optics is, in essence, the study of how light interacts with structures between 100 nanometers to a nanometer, or a billionth of a meter. In case you have not yet figured it out, nano means very, very tiny.
The other thing you need to understand about Gbur’s work is that it is purely theoretical. When you are studying something so tiny, and trying to make light do things few have made light do before, you don’t do that kind of work in a lab, you do it with a pen and paper, working with equations, or with a computer, writing software code.
That is not to say Gbur doesn’t do his work with end applications in mind, he says.
“Reasons for such studies range from the purely scientific to the almost mundanely practical,” says Gbur of his work. “Much of what we are looking at is related to overcoming the resolution limitations of traditional optical imaging systems, such as CD players, microscopes or x-rays.”
Using the example of a CD player, Gbur explains the limitations of what he calls traditional optics versus nano-optics.
"In a CD player, the density of information that can be stored on a disc is limited by the width of the light beam used to read it, which is typically no smaller than a wavelength. Therefore there is a finite amount of information that can be stored on a disc, using traditional optics," says Gbur. "Suppose, however, I first force my light beam to pass through a tiny hole much smaller than the wavelength. When the light comes out of the other side, it will form a hole-sized spot that will quickly spread -- unless I also put the disc surface very close to the hole exit. With this configuration, I can illuminate a subwavelength section of a compact disc and in principle pack more data onto the disc as a whole. A lot of what I've been doing has been developing computational tools to study what happens to light in these nanoscale-size systems."
Unfortunately, the techniques that Gbur is researching are limited by a fundamental problem, he says. By “forcing” light through holes smaller than a wavelength, the strength of light is reduced. Gbur likens it to trying to squeeze Nerf balls through an opening smaller than the size of the ball — you can still squish the balls to get them through, but not easily. The inability to effectively force light through a small hole limits the effectiveness of all the nano-optics’ applications. And that is where another aspect of Gbur’s research interests comes into play: surface plasmons.
In 1998, a group of researchers discovered that, when they shined light through an array of subwavelength-sized holes in a thin film of silver, the strength of the light transmitted through the holes was much greater than predicted. These results were attributed to the presence of electron-density surface waves, known as surface plasmons.
According to Gbur, a surface plasmon is a traveling wave oscillation of electrons on the surface of certain metals containing the right material properties. Because a plasmon consists of oscillating electric charges, they have an electromagnetic field associated with them, which also carries energy.
“It turns out these plasmons assist in funneling more light through the holes, thus solving the problem of light throughput in nano-optics,” Gbur says.
Currently, Gbur’s research focuses on studying these surface plasmons and their effects on nano-optics and potential applications.
A Public Intellectual for the New Millennium
As his Nerf ball analogy belies, Gbur has a particular talent for illustrating complicated science lessons.
“I believe I am successful as a blogger and teacher because I personally need simple ways to visualize problems, so I’m then able to describe it to others,” he says.
Gbur maintains a popular blog (skullsinthestars.com) that covers topics in physics and optics, the history of science, classic pulp fantasy and horror fiction, and, what he refers to as “the surprising intersections between these areas.” He got his blog title from a 1929 short story by the same title which features, he says, “conflict between the [protagonist’s] fundamentalism and the realities of a world which is not always black and white.”
“Blogging give me a way to talk about science in a way that is not just geared toward specialists,” Gbur says. “Through it, I not only reach out to people in my field but in other scientific fields and to general readers, as well.”
Begun in 2007, the blog now averages between 400 and 1000 views per day, and it has had over a half-million visitors since its inception.
You may also find Gbur on the social media sharing site, Twitter, as “@drskyskull.” He “tweets” an update and a link when he has posted a new piece on his blog, but he also uses the platform for shorter back-and-forth with his colleagues and some personal fun. He now has over 800 followers.
Gbur says playing around on Twitter gives him something to do while he sits in front of the television at night, although one cannot imagine he has enough spare time for such. He adds that blogging (and “tweeting”) are also good ways for him to practice writing accessibly for a more general audience than that for his typical academic papers.
“It is also an outlet for me to investigate subjects that I otherwise have little time to pursue,” says Gbur.
The Invisibility Man
Gbur plans to write a popular science book on the history of invisibility, a subject he has been interested in since his graduate school days.
“The history of invisibility goes back over 100 years,” says Gbur. “There’s a very crude invisibility device that was written about in 1902 that I actually bought the ingredients for and want to put together.”
He was recently invited to write a guest post on the topic, “Invisibility: After several years of research, it's just gotten weirder,” on the website of the popular science magazine, Scientific American.
Gbur likely defines “invisibility” differently than the rest of us, and while he says the odds of ever developing something like Harry Potter’s invisible cloak are unlikely, there is a real chance that a “cloak” of sorts could be developed, which could shield objects, perhaps not necessarily from view, but from radar detection or from electromagnetic or sound waves.
“It could be possible to create some type of technology to protect electronic devices from MRI machines, for example,” says Gbur. “People have suggested using the same type of technology to protect buildings from earthquakes, to guide earthquake waves around a building. There are a lot of possibilities to make something, to a certain extent, invisible.”
While he is a student of the history of invisibility, it is also a field in which he has done some original research (in fact, some of his research on the subject was part of his PhD dissertation). Gbur says that the area of invisibility research is promising and one that he plans on delving into again soon.
“That is the beauty of being a theorist,” Gbur says. “I like to keep a lot of projects in the air at the same time, and if I get stumped on something, it’s easy to move back and forth.”
The Physics of Flying
Just as Gbur begins his week with a figure skating lesson (which, he would clarify, he has on Wednesdays and Fridays, as well), he typically ends his week by throwing himself from an airplane with a half dozen of his closest friends. Most weekends, Gbur joins a local group on an airstrip in upstate South Carolina for something called “formation sky diving.”
He jokes that skydiving is a way for him to experience the law of physics firsthand, but in truth Gbur started this hobby — of which his wife only grudgingly approves — in graduate school at the same time he started skating. He began them both, he said, to get himself out of a rut, to challenge himself and make him go beyond his comfort zone.
“You jump out of a plane together and make formations mid-air and see how many you can do before you have to pull your chute,” Gbur explains. “Initially people view it as just purely an adrenaline rush, but it is open-ended in terms of challenging yourself.”