A research team from the State Key Laboratory of Intelligent Manufacturing Equipment and Technology, Huazhong University of Science and Technology, and Optics Valley Laboratory, China, has developed a comprehensive femtosecond laser-acoustic modeling and simulation framework to advance nondestructive testing (NDT) of metal nanofilms.
The study, titled “Femtosecond Laser-Acoustic Modeling and Simulation for AlCu Nanofilm Nondestructive Testing”, was authored by Zhongyu Wang, Jing Min, Jing Hu, Zehan Wang, Xiuguo Chen, Zirong Tang, and Shiyuan Liu, and presents a major leap in photoacoustic detection technology—a technique vital for assessing the thickness, integrity, and defects in nanostructured materials used in electronics, optics, and material science.
Revolutionizing Ultrasonic Inspection at the Nanoscale
Photoacoustic detection has long been recognized for its precision in evaluating nanomaterials, yet most existing research has focused on picosecond and nanosecond laser systems. In contrast, femtosecond lasers, with their ultrashort pulse durations, offer unprecedented temporal and spatial resolution, enabling detailed insight into material behavior at the nanoscale.
However, the theoretical understanding of femtosecond laser-based photoacoustic NDT has been limited, with no complete physical model linking laser excitation to acoustic signal measurement. This gap has traditionally forced researchers to rely on empirical adjustments of laser parameters, resulting in lower efficiency and accuracy.
The team’s newly developed comprehensive physical model changes that. By combining the two-temperature model (TTM)—which differentiates between electron and lattice temperatures—with an acoustic wave generation and detection model, the researchers provide a holistic understanding of laser-induced acoustic dynamics in nanofilms.
Simulation and Experimental Validation
The simulation model, developed using finite difference and finite element methods, visualizes the complete ultrafast laser-material interaction process during femtosecond photoacoustic testing of AlCu nanofilms. It enables precise calculations of temperature fields, stress, and strain distributions, while also determining the damage threshold of the laser for AlCu materials.
By systematically varying key parameters—laser fluence, pulse duration, and wavelength—the team demonstrated how these factors influence detection performance. Experiments conducted on 500 nm-thick AlCu nanofilms validated the numerical predictions, with the results showing excellent agreement between simulation and experiment.
Implications for the Future of Nondestructive Testing
The research offers critical insights into optimizing laser parameters for improved photoacoustic signal quality and detection accuracy. The developed model provides a scientific foundation that eliminates the need for trial-and-error parameter tuning, thus improving efficiency, repeatability, and reliability in nanoscale nondestructive testing.
By bridging the gap between laser physics, thermal dynamics, and acoustic signal modeling, the study represents an important step toward next-generation NDT technologies that are capable of detecting minute defects and variations in advanced thin-film materials.
The findings have significant engineering and industrial implications, particularly in fields where precision and reliability are critical — such as semiconductor manufacturing, microelectronics, and advanced materials research.
