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Value of silver lining is priceless to Simin Zhang


Some of the most gratifying moments in life greet us during the rockiest of circumstances. Simin Zhang just celebrated her first year in the United States (and as a Buckeye), and her academic timeline approached an abrupt curve as U.S. Immigration and Customs Enforcement issued a rule requiring all international students whose classes were only online to vacate the country. Computational research like hers allowed Simin to work remotely while Columbus and most of the country adjusted to safety measures and distanced operations. In what had been a rollercoaster of a month ended up being a gift to the young and driven student pursuing her dreams.

photo of Simin Zhang, Ohio State
Simin Zhang

She had arrived in Columbus last July to begin her PhD research in materials science and engineering. Under the direction of MSE Professor Enam Chowdhury, Simin has spent the past year developing a computational framework for the damage threshold of optical coatings as part of a Department of Energy grant (Phase I) that included a Small Business Technology Transfer (STTR) component. It’s a design that allowed Ms. Zhang to work with industry and academia to solve real-world problems. The reward for each stakeholder would be the granting of Phase II by the Department of Energy.

Most cannot attribute their academic focus to confusion, but Simin was smitten with straightening things out – complex things that combined engineering, physics, math, critical thinking.

“Engineering has been fascinating to me since high school, because engineers are those who invent and design amazing things, like bridges, rockets, lasers, etc. However, mysteries increased as I spent years learning physics and math, solving questions for exams, but never had a chance to practice the knowledge in solving real-world problems, so I chose engineering for my undergraduate major because of the confusion.

As I became a graduate student, I was fascinated by high intensity laser systems larger than a tennis court. A seed pulse is generated, amplified, stretched, compressed, shaped in a journey of light path, where tons of physics play their roles. And the development of high-powered lasers can help deepen our understanding of astrophysics and search for solutions with clean energy. But as a laser pulse must go through thousands of optics before the final output, failure of any single one can stop us from achieving higher power. Therefore, my motivation is that if a problem on the materials science side can be solved first, numerous possibilities on the physics side will be


Simin Zhang young girl, Ohio State
A younger Simin Zhang dreamed of being an engineer. Credit: S. Zhang

Simin was attracted to Ohio State because of the SCARLET laser, one of a handful of ultra-high intensity laser facilities in the world. SCARLET laser is capable of producing a peak power of about 400 TW, which is eighty times higher than the total power consumption of the entire United States. This capacity provides a great platform for a wide variety of studies associated with high-energy density physics.

Professor Enam Chowdhury, who has a special interest in ultraintense and high-energy density laser matter interaction, led the design and construction of SCARLET laser. “I watched a presentation given by Enam at an academic conference in 2018, and the study of ultrafast laser and solid interaction by his group interested me very much," says Zhang, adding that Ohio State “is definitely a wonderful place for students who want to study science and engineering of high power lasers”.

The recent events concerning the future of international students studying at our nation’s colleges and universities were a harbinger of confusion not anticipated by Simin or the other 1.1 million international students in America. With educational norms offset by a global pandemic, most educational programs are going virtual. This transition resulted in a climate of uncertainty that set the nerves of international student on edge until the issue was overruled on July 14.

“It’s absolutely a huge relief for me,” shares Simin. “It had been a tough month of real confusion and anxiety. I am really grateful that the Ohio State community responded very swiftly with all the supportive messages and effective actions. It is also very uplifting for me to see so many university communities standing up for international students’ well-being in such a difficult time.”

Professor Chowdhury shares Simin’s sentiments, having been an international student himself. Almost immediately after the overruling, both had something else to celebrate when the Department of Energy announced the project would progress to Phase II with the help of a $1.1M grant. Dr. Chowdhury praises Simin’s contributions over the past year, “Simin's work in developing a computational framework for solving this problem was crucial for this $1.1 million renewal.”

The goal of Phase I was to improve the damage threshold of the coatings through a computational approach. The damage threshold of coatings of critical components is a bottleneck of high-intensity, high-power lasers, which will become the tools for next generation particle accelerators, cancer therapy, medical isotope production and exploration of non-linear quantum vacuum, as charted by the 2018 National Academy of Science Report and the recent national Brightest Light Initiative report, for which Dr Chowdhury serves as a member.

Optical materials and coatings that can withstand a billion intense laser shots while manipulating light at nanometer spatial and femtosecond temporal scale are essential for the development of this technology. However, the coatings are subject to laser-induced damage, especially in the regime of ultrashort pulses, via non-thermal melting and ablation processes.

Ms. Zhang’s work focused on developing a computational framework that simulates the dynamics of laser solid interaction in a multilayer, dielectric thin-film stack. The simulation results would qualitatively and quantitatively determine the damage threshold of the input designs. As a result, the design can be improved before fabrication.

While Simin’s academic timeline will culminate with a Doctor of Philosophy degree in 2024, a monumental month has etched its place on her journey. The apprehension that opened the month of July was eclipsed by joy. “It is certainly a silver lining for me in a month full of disappointing news. I am very grateful that the Department of Energy valued our work in Phase I and granted us Phase II in such a difficult time. This refreshing start motivates me a lot, and I am very excited to get to work on a broader extent of research in Phase II,” says Zhang.

The future Dr. Simin Zhang hopes to work as a faculty member in a university or a researcher in a lab in the field of optical engineering.


About the project:

Title: Interference coatings for high energy and average power femtosecond-class lasers in the 0.8-2mm wavelength range

The STTR work is in collaboration with XUV Lasers of Fort Collins, CO. Other academic partners are Colorado State University and University of New Mexico.

Dr. Enam Chowdhury is the PI of Phase II. Company co-PI is Dr. Carmen S. Menoni.

Term for Phase II: 2 years

Grant amount: $1.1M

by Libby Culley, Communications for the Department of Materials Science & Engineering ׀