Electrons Dynamics Control in Femtosecond Laser Micro/Nanofabrication: Russell Severance Springer Colloquium

Seminar | January 29 | 4-5 p.m. | 3110 Etcheverry Hall

 Professor Lan Jiang, Changjiang Distinguished Professor; Beijing Institute of Technology

 Department of Mechanical Engineering (ME)

Abstract: During femtosecond laser fabrication, photons are mainly absorbed by electrons, and the subsequent energy transfer from electrons to ions is of picosecond order. Hence, lattice motion is negligible within the femtosecond pulse duration, whereas femtosecond photon-electron interactions dominate the entire fabrication process. Therefore, femtosecond laser fabrication must be improved by controlling localized transient electron dynamics, which poses a challenge for measuring and controlling at the electron level during fabrication processes. Pump-probe spectroscopy presents a viable solution, which can be used to observe electron dynamics during a chemical reaction. In fact, femtosecond pulse durations are shorter than many physical/chemical characteristic times, which permits manipulating, adjusting, or interfering with electron dynamics. Hence, we proposed to control localized transient electron dynamics by temporally or spatially shaping femtosecond pulses, and further to modify localized transient materials properties, and then to adjust material phase change, and eventually to implement a novel fabrication method. This talk covers our progresses over the 11 years regarding electrons dynamics control (EDC) by shaping femtosecond laserpulses in micro/nanomanufacturing: (1) Theoretical models were developed to prove EDC feasibility and reveal its mechanisms; (2) on the basis of the theoretical predictions, many experiments are conducted to validate our EDC-based femtosecond laser fabrication method. Some examples are presented, which proves that the proposed method can significantly improve fabrication precision, quality, throughput and repeatability and effectively control micro/nanoscale structures; and (3) As examples of practical applications, our method was employed to fabricate some key structures, for which commercialized equipment has been developed and sold for broad applications in industry.

Biography: Dr. Lan Jiang, the Changjiang Distinguished Professor at the Beijing Institute of Technology, received the Second Award of National Natural Sciences (Central Government of China), Ho Leung Ho Lee Innovation Award, the First Award of Natural Sciences (Ministry of Education of China), the First Award of Innovation (Ministry of Education of China), and National Outstanding Young-Scientist Award (National Natural Science Foundation of China). Over the past twelve years, as the Principal Investigator, he has received 25 grants totaling RMB181 million (approximately $26 million including facilities). He was elected as the National Leading Researcher for S&T Innovations and the Leader of Innovation Group of Ministry of Education of China. Dr. Jiang serves as Chief Scientist of National Basic Research Program of China, Director of National Innovation Center for High-Precision Micro-Fabrication, and Dean of the School of Mechanical Engineering at the Beijing Institute of Technology. He is an ASME Fellow, OSA Fellow, and ISNM Fellow. Dr. Jiang has authored 247 journal papers and 60 patents. He has delivered 19 plenary/keynote presentations and 50 invited talks in mainstream international conferences.

 cgrigoro@berkeley.edu, 510-642-2525