Making airfield assessments automatic, remote, and safe

U.S. Air Force engineer and PhD student Randall Pietersen is using AI and next-generation imaging technology to detect pavement damage and unexploded munitions.

In 2022, Randall Pietersen, a civil engineer in the U.S. Air Force, set out on a training mission to assess damage at an airfield runway, practicing “base recovery” protocol after a simulated attack. For hours, his team walked over the area in chemical protection gear, radioing in geocoordinates as they documented damage and looked for threats like unexploded munitions.

The work is standard for all Air Force engineers before they deploy, but it held special significance for Pietersen, who has spent the last five years developing faster, safer approaches for assessing airfields as a master’s student and now a PhD candidate and MathWorks Fellow at MIT. For Pietersen, the time-intensive, painstaking, and potentially dangerous work underscored the potential for his research to enable remote airfield assessments.

“That experience was really eye-opening,” Pietersen says. “We’ve been told for almost a decade that a new, drone-based system is in the works, but it is still limited by an inability to identify unexploded ordnances; from the air, they look too much like rocks or debris. Even ultra-high-resolution cameras just don’t perform well enough. Rapid and remote airfield assessment is not the standard practice yet. We’re still only prepared to do this on foot, and

that’s where my research comes in.”

Pietersen’s goal is to create drone-based automated systems for assessing airfield damage and detecting unexploded munitions. This has taken him down a number of research paths, from deep learning to small uncrewed aerial systems to “hyperspectral” imaging, which captures passive electromagnetic radiation across a broad spectrum of wavelengths. Hyperspectral imaging is getting cheaper, faster, and more durable, which could make Pietersen’s research increasingly useful in a range of applications including agriculture, emergency response, mining, and building assessments.

Military students innovate technology solutions for US Special Operations Command

Working with mentors and military operators, cadets are addressing challenges in such areas as autonomy, data analytics, communications, and blood delivery.

All eyes were on the robot-dog pacing the hangar on Hanscom Air Force Base. The robot was just one technology, among small drones, autonomous mapping vehicles, and virtual-environment simulators, set up for military cadets to interact with. The goal was to open cadets' minds to possibilities. Over the next year, they will be applying such technologies to challenges facing the U.S. Special Operations Command (USSOCOM) for a program called SOCOM Ignite.

SOCOM Ignite connects military students with research scientists and special operations forces to address SOCOM’s pressing technology challenges, while ushering in new generations of technology-savvy officers and operators. Now in its fourth year, the program invites cadets from across the nation’s military academies and Reserve Officers' Training Corps (ROTC) programs to participate. 

"We started as just a two-day hackathon having less than 10 cadets, and now we are a year-long program with more than 80 cadets from more than 19 different universities, representing the Army, Navy, and Air Force. We hope to extend to the Marines and any other group out there," says Raoul Ouedraogo, who helped establish the program and is a leader within MIT Lincoln Laboratory’s Homeland Sensors and Analytics Group.

incoln Laboratory researchers serve as the technical mentors in the program. To start the program this year, they offered new "innovation incubators," or crash courses on the basics of machine learning and autonomy, two topics of high interest to SOCOM. Following those sessions, a formal kick-off ceremony brought in SOCOM leaders to explain the impact of the program for the command’s mission. SOCOM is the nation’s only unified combatant command that oversees special operations forces across all branches of the armed services. 

"What makes SOCOM so important to the Department of Defense is that we are pathfinders. We look at advanced concepts, take those visions and dreams, and make them real," says SOCOM Senior Enlisted Leader (Retired) Greg Smith. 

"We have a mix of academy cadets and ROTC students, providing diverse perspectives. We have access to users in the SOCOM community, whose time is precious, and to technology mentors, who do this for a living. Those three things make this a unique program," Lisa Sanders, the director of science and technology for Special Technology, and Logistics, USSOCOM, said at the ceremony. "SOCOM also has acquisition authority — people who get ideas on the market. The ideas that you come up with will make a meaningful difference."Operations Forces, Acquisition,

A dive into the “almost magical” potential of photonic crystals

In MIT’s 2025 Killian Lecture, physicist John Joannopoulos recounts highlights from a career at the vanguard of photonics research and innovation.

When you’re challenging a century-old assumption, you’re bound to meet a bit of resistance. That’s exactly what John Joannopoulos and his group at MIT faced in 1998, when they put forth a new theory on how materials can be made to bend light in entirely new ways.

“Because it was such a big difference in what people expected, we wrote down the theory for this, but it was very difficult to get it published,” Joannopoulos told a capacity crowd in MIT’s Huntington Hall on Friday, as he delivered MIT’s James R. Killian, Jr. Faculty Achievement Award Lecture.

Joannopoulos’ theory offered a new take on a type of material known as a one-dimensional photonic crystal. Photonic crystals are made from alternating layers of refractive structures whose arrangement can influence how incoming light is reflected or absorbed.

In 1887, the English physicist John William Strutt, better known as the Lord Rayleigh, established a theory for how light should bend through a similar structure composed of multiple refractive layers. Rayleigh predicted that such a structure could reflect light, but only if that light is coming from a very specific angle. In other words, such a structure could act as a mirror for light

shining from a specific direction only.

More than a century later, Joannopoulos and his group found that, in fact, quite the opposite was true. They proved in theoretical terms that, if a one-dimensional photonic crystal were made from layers of materials with certain “refractive indices,” bending light to different degrees, then the crystal as a whole should be able to reflect light coming from any and all directions. Such an arrangement could act as a “perfect mirror.”

The idea was a huge departure from what scientists had long assumed, and as such, when Joannopoulos submitted the research for peer review, it took some time for the journal, and the community, to come around. But he and his students kept at it, ultimately verifying the theory with experiments.

That work led to a high-profile publication, which helped the group focus the idea into a device: Using the principles that they laid out, they effectively fabricated a perfect mirror and folded it into a tube to form a hollow-core fiber. When they shone light through, the inside of the fiber reflected all the light, trapping it entirely in the core as the light pinged through the fiber. In 2000, the team launched a startup to further develop the fiber into a flexible, highly precise and minimally invasive “photonics scalpel,” which has since been used in hundreds of thousands of medical procedures including a surgeries of the brain and spine.

“And get this: We have estimated more than 500,000 procedures across hospitals in the U.S. and abroad,” Joannopoulos proudly stated, to appreciative applause.

Joannopoulos is the recipient of the 2024-2025 James R. Killian, Jr. Faculty Achievement Award, and is the Francis Wright Davis Professor of Physics and director of the Institute for Soldier Nanotechnologies at MIT. In response to an audience member who asked what motivated him in the face of initial skepticism, he replied, “You have to persevere if you believe what you have is correct.”

Bending light

In his lecture, which he titled “Working at the Speed of Light,” Joannopoulos took the audience through the basic concepts underlying photonic crystals, and the ways in which he and others have shown that these materials can bend and twist incoming light in a controlled way.

As he described it, photonic crystals are “artificial materials” that can be designed to influence the properties of photons in a way that’s similar to how physical features in semiconductors affect the flow of electrons. In the case of semiconductors, such materials have a specific “band gap,” or a range of energies in which electrons cannot exist.

In the 1990s, Joannopoulos and others wondered whether the same effects could be realized for optical materials, to intentionally reflect, or keep out, some kinds of light while letting others through. And even more intriguing: Could a single material be designed such that incoming light pinballs away from certain regions in a material in predesigned paths?

“The answer was a resounding yes,” he said.

Joannopoulos described the excitement within the emerging field by quoting an editor from the journal Nature, who wrote at the time: “If only it were possible to make materials in which electromagnetic waves cannot propagate at certain frequencies, all kinds of almost-magical things would be possible.”

Joannopoulos and his group at MIT began in earnest to elucidate the ways in which light interacts with matter and air. The team worked first with two-dimensional photonic crystals made from a horizontal matrix-like pattern of silicon dots surrounded by air. Silicon has a high refractive index, meaning it can greatly bend or reflect light, while air has a much lower index. Joannopoulos predicted that the silicon could be patterned to ping light away, forcing it to travel through the air in predetermined paths.

In multiple works, he and his students showed through theory and

In multiple works, he and his students showed through theory and experiments that they could design photonic crystals to, for instance, bend incoming light by 90 degrees and force light to circulate only at the edges of a crystal under an applied magnetic field.

“Over the years there have been quite a few examples we’ve discovered of very anomalous, strange behavior of light that cannot exist in normal objects,” he said.

In 1998, after showing that light can be reflected from all directions from a stacked, one-dimensional photonic crystal, he and his students rolled the crystal structure into a fiber, which they tested in a lab. In a video that Joannopoulos played for the audience, a student carefully aimed the end of the long, flexible fiber at a sheet of material made from the same material as the fiber’s casing. As light pumped through the multilayered photonic lining of the fiber and out the other end, the student used the light to slowly etch a smiley face design in the sheet, drawing laughter from the crowd.

As the video demonstrated, although the light was intense enough to melt the material of the fiber’s coating, it was nevertheless entirely contained within the fiber’s core, thanks to the multilayered design of its photonic lining. What’s more, the light was focused enough to make precise patterns when it shone out of the fiber.

“We had originally developed this [optical fiber] as a military device,” Joannopoulos said. “But then the obvious choice to use it for the civilian population was quite clear.”

“Believing in the goodness of people and what they can do”

He and others co-founded Omniguide in 2000, which has since grown into a medical device company that develops and commercializes minimally invasive surgical tools such as the fiber-based “photonics scalpel.” In illustrating the fiber’s impact, Joannopoulos played a news video, highlighting the fiber’s use in performing precise and effective neurosurgery. The optical scalpel has also been used to perform procedures in larynology, head and neck surgery, and gynecology, along with brain and spinal surgeries.

Omniguide is one of several startups that Joannopoulos has helped found, along with Luminus Devices, Inc., WiTricity Corporation, Typhoon HIL, Inc., and Lightelligence. He is author or co-author of over 750 refereed journal articles, four textbooks, and 126 issued U.S. patents. He has earned numerous recognitions and awards, including his election to the National Academy of Sciences and the American Academy of Arts and Sciences.

The Killian Award citation states: “Professor Joannopoulos has been a consistent role model not just in what he does, but in how he does it. … Through all these individuals he has impacted — not to mention their academic descendants — Professor Joannopoulos has had a vast influence on the development of science in recent decades.”

At the end of the talk, Yoel Fink, Joannopoulos’ former student and frequent collaborator, who is now professor of materials science, asked Joannopoulos how, particularly in current times, he has been able to “maintain such a positive and optimistic outlook, of humans and human nature.”

“It’s a matter of believing in the goodness of people and what they can do, what they accomplish, and giving an environment where they’re working in, where they feel extermely comfortable,” Joannopoulos offered. “That includes creating a sense of trust between the faculty and the students, which is key. That helps enormously.”