Feature Story | 7-Dec-2023

Soham Saha is developing the next generation of X-ray tools

The Maria Goeppert Mayer Fellow describes his work converting laser light into small, adjustable X-ray sources

DOE/Argonne National Laboratory

Like other types of light, X-rays can take varying forms — from the camera a dentist uses to illuminate your teeth to the far more powerful rays generated at the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science user facility at DOE’s Argonne National Laboratory. Soham Saha is exploring methods to generate X-rays that would make the beams far easier to access across a range of scientific fields.

Saha received his Ph.D. in electrical engineering in 2021 from Purdue University, where he specialized in optics and materials science. Previously, he earned his bachelor's and master's degrees in electrical engineering at the National University of Singapore. He joined Argonne in the fall of 2022 as a Maria Goeppert Mayer Fellow.

The Maria Goeppert Mayer Fellowship is an international award given to outstanding doctoral scientists and engineers to help them develop their careers in Argonne’s high-impact research environment. The fellowship honors Maria Goeppert Mayer, a theoretical physicist who earned the Nobel Prize in Physics in 1963 for her work at Argonne proposing a mathematical model for the structure of nuclear shells of the atomic nucleus. The fellowship provides early-career scientists the opportunity to pursue their own research directions, with the support of a sponsor and up to three years of funding.

Here, Saha talks about his career and his experience in the program so far.

Q: What are you working on at Argonne?

A: My job is to make X-ray sources using optical lasers as a source. The idea is that we take a very intense laser beam operating at a long wavelength, and we shine it onto a specific material. When the laser light bounces off the material’s surface, it can create a high-energy (short wavelength) X-ray photon, through a process called high harmonic generation. A possible application for this technology could be shrinking X-ray machines down to the size of a computer chip.

There are other ways to generate X-rays, such as the particle accelerator at the APS. But high harmonic generation offers a way to make less powerful — though still very useful — X-ray beams with controllable optical properties such as amplitude, phase and polarization. High-harmonic generation can also produce attosecond pulses, which can be used to probe how electrons behave. If this sounds familiar, it’s because the 2023 Nobel Prize in physics just went to the team that first generated these ultrashort pulses — an attosecond is a billionth of a billionth of a second. Attosecond processes are important to many mechanisms in biology, chemistry and physics.

Q: Why are small X-ray sources desirable?

A: Making X-rays from lasers will give us a greater degree of control. We can manipulate the properties of the X-ray beam to look closely at different types of materials. You could also imagine transferring this technology to the medical sector, where you would be able to have a very local scan of a body part with just the right amount of X-ray radiation.

If we can have a high-energy, high-efficiency X-ray source, one thing it would definitely do is lower the prices of conventional X-ray technology that we use in laboratories today.

Q: Why did this fellowship appeal to you?

A: The biggest thing that appealed to me about this fellowship is the enormous freedom that it gave me to propose a project from the ground up. I also wanted to have a transition from my original field, which is making optical structures that work with traditional light, to working with high-energy optics. With this fellowship, I saw that I could leverage my experience, but work in a slightly different field, and I could have flexibility to pursue different approaches to solving this problem. And at Argonne, I have access to a lot of expertise from a lot of different areas of science. I also use Argonne's Center for Nanoscale Materials (a DOE Office of Science user facility) to fabricate the nanoscale structures for my research and to characterize them with high-power lasers.

Q: How did you become interested in this topic?

A: One of my aunts got diagnosed with cancer, and it was pretty late-stage. Her treatment involved using X-ray radiation therapy to kill the cancer cells. I thought, with high harmonic generation, maybe at some stage we can start generating X-ray beams with such precision that you can focus it down to a cellular size for medical applications. All of these ideas were playing around in my head. I had a collaboration with my current supervisor here, Rich Schaller, and I asked him, would this be a good idea to write up? He said sure, let's try.

Q: What do you like to do when you're away from work?

A: One of my hobbies is writing science fiction, and I do a lot of portrait-sketching these days. I also have two cats that take up some time. Sometimes when I don't have experiments for a few weeks, and I'll be running simulations, processing data and writing from home, I foster kittens.

Q: What advice do you have for others interested in following your career path?

A: Picking a project that you really want to do is very important. Don't decide, “Okay, I'll just do this one project and once it's done, I'll do the thing I want.” There will always be an endless stream of projects that others want you to do, but you need to find out what you really like. Once you find something, you have to latch onto it and make sure that you don't get distracted.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.