Xiaobing Zhu has been named the first recipient of the Mansoor Sheik-Bahae Best Dissertation Award for her groundbreaking work titled Phase Nanoscopy with Correlated Frequency Combs. Zhu earned her Ph.D. in Optical Science and Engineering from The University of New Mexico's Department of Physics and Astronomy in Summer 2025.

Zhu began her academic journey at UNM in 2019 after earning a master's degree in optical engineering from Sichuan University in China. She joined the research group of Professor Jean-Claude Diels as a research assistant. Although she started with no background in lasers or electronics, she was tasked with constructing a femtosecond optical parametric oscillator (OPO) and its pump laser, a mode-locked Ti:sapphire laser-systems that require micrometer precision to align, often without visual cues.

"Despite having no prior background, I was solely responsible for constructing a femtosecond optical parametric oscillator (OPO)," Zhu said. "With no collaborators aside from my supervisor, I independently built and rebuilt the system multiple times from scratch. This experience deeply strengthened my expertise in ultrafast optics, problem-solving, and experimental design."

Her dissertation advances phase sensing to the quantum limit using intracavity phase interferometry with correlated frequency combs. By generating two synchronized ultrashort pulses in the same cavity, introducing a phase shift between them through the interaction with a physical quantity, and detecting the resulting beat note, she achieved a phase measurement resolution of 0.033 nanoradian-equivalent to 0.006 femtometers in displacement and 0.85 millihertz in frequency-comparable to the precision of LIGO.

To overcome the challenge of working with invisible infrared light (near 1200 nm), Zhu employed second harmonic generation (blue light) for system alignment. The process demanded careful pump power tuning to protect the gain crystal, further demonstrating her technical finesse.

Zhu's success was hard-earned, with many long nights and weekends spent alone in UNM's Center for High Technology Materials. Her work not only achieved state-of-the-art precision but also opens new avenues for compact, quantum-limited sensors in metrology and fundamental physics.

"Mansoor Sheik-Bahae has been an inspiring figure in my academic journey. His teachings in laser physics and nonlinear optics profoundly shaped my understanding and laid the foundation for much of my subsequent research. Being honored with the Mansoor Sheik-Bahae Best Dissertation Award was a tremendous privilege and a deeply meaningful recognition. It has further motivated me to continue pursuing research beyond graduation," said Zhu.

"The award honors Distinguished Professor Mansoor Sheik-Bahae, who passed away from lymphoma in July, 2024. He is greatly missed. We wanted to honor Mansoor's illustrious career in optics by setting up a fund to establish this prize. We are so grateful for the many generous donations that will allow us to hand out this award for decades to come. Xiaobing completed a very challenging dissertation, which required tremendous perseverance."

- Richard Rand, chair, Physics & Astronomy

Zhu is also first author on the research titled, "Simple analysis of Gaussian pulses and beams in mode-locked lasers" published in the Applied Optics. The work presents an interwoven space-time domain approach for analyzing the evolution of Gaussian beams and pulses, as well as evaluating the stability of nonlinear laser cavities. This method provides a practical framework for characterizing Gaussian beam and pulse behavior and aids in the design of stable, mode-locked laser systems.

Zhu credits her success to the mentorship and support of her advisor, colleagues, and community at UNM.

"My deepest gratitude goes to Dr. Jean-Claude Diels, whose knowledge, patience, and optimism have shaped my academic and personal growth," she said. "I'm also thankful to Dr. Matthias Lenzner for his guidance and friendship, and to my family and lab mates for their encouragement through every challenge."

Reflecting on her time at UNM, Zhu said it was transformative.

"Academically, I learned resilience, critical thinking, and developed deep expertise in ultrafast lasers and precision phase sensing. Personally, I gained confidence, patience, and a strong sense of responsibility. UNM gave me not just an academic foundation but a supportive community."

Honoring a Legacy: Professor Mansoor Sheik-Bahae

The award honors the late Distinguished Professor Mansoor Sheik-Bahae, who died away in July 2023 after a battle with lymphoma. A world-renowned physicist and Optica Fellow, Sheik-Bahae was recognized for seminal contributions to ultrafast nonlinear optics, solid-state laser cooling, and the widely adopted Z-scan technique.

At UNM, Sheik-Bahae served as general chair of the Optical Science and Engineering Program and director of the Consortium for Laser Cooling in Solids. He also held leadership roles in scientific organizations including Optica, CLEO, and SPIE, and served as a topical editor for the Journal of the Optical Society of America B.

Known for his generosity and mentorship, Sheik-Bahae left a profound legacy at UNM and in the global optics community. The award in his name ensures that his spirit of excellence and innovation will continue to inspire future generations of scientists.