At the same power, the shorter the laser pulse duration, the higher the instantaneous power. When the laser pulse duration is as short as the trillionth of a second level, the instantaneous peak power can exceed a trillion watts, more than hundreds of times the combined installed power of all the world's power plants. This is the femtosecond laser.
By adjusting the nature of the femtosecond laser pulse in the time, space and frequency domains, the femtosecond laser will become a shape, nature of the adjustable, indestructible flexible tool, in the micron, nano-scale to complete high-precision cutting, punching, leveling and so on, and even be able to realize the electronic level of the regulation of the ...... more than 20 years ago, Jiang Lan saw the femtosecond laser The application of femtosecond lasers has great potential.
Now, in the School of Mechanical and Vehicle Engineering of Beijing Institute of Technology, Jiang Lan and his team are the first to predict the shape of femtosecond laser processing in the international arena, the first to put forward a new principle of femtosecond laser electronic dynamic control manufacturing, the first to realize the electronic level of laser manufacturing active control, the first to develop the first set of quasi-three-dimensional ultra-fast continuous observation system across the scales, the first to achieve the observation of the electronic level of laser manufacturing, the first to achieve a major engineering applications of femtosecond laser manufacturing, and the first to realize the femtosecond laser manufacturing, the first to realize major engineering applications of femtosecond laser manufacturing, and the first to realize large-scale industrial applications of femtosecond laser manufacturing.
Jiang Lan (third from left) guides students to carry out experiments on femtosecond laser electron dynamic modulation processing.
Since the birth of mankind's first ruby laser in 1960, scientists have continued to push the performance of lasers to be faster and stronger. In the 1980s, researchers found that when the laser pulse duration is as short as one-trillionth of a second level, the intensity of more than one trillion watts in the ultrafast, ultra-intense interval, the classical theoretical model has not been able to explain this ultra-fast and ultra-intense electromagnetic field and matter interaction mechanism, which has become a bottleneck restricting the development of femtosecond laser. At the beginning of this century, Jiang Lan entered the field of femtosecond laser manufacturing research.
Undergraduate, Jiang Lan has a strong interest in physics, "'relativity', 'quantum mechanics' are then the direction of my research, represented by laser high-energy beam manufacturing is essentially the interaction of energy and matter, is the direction I am very interested in! The high energy beam manufacturing represented by lasers is essentially the interaction between energy and matter, which is the direction I am very interested in".
Without a team, without a project, focusing on just a research branch of the third-level disciplinary field, recalling the situation more than 20 years ago when he was alone in the bureau, Jiang Lan's mouth was flushed with a trace of happiness, reminiscent of the smile. "It was a wonderful time to dive into research alone without being disturbed."
Six years later, Jiang Lan made a breakthrough in the theoretical study of femtosecond laser fabrication. He proposed an improved dual-temperature model, which extended the scope of application of the classical dual-temperature equation from the electron low-temperature region to an arbitrary electron temperature range, improving the accuracy of threshold prediction for femtosecond laser processing. He established a plasma quantum model to predict the shape of femtosecond laser processing for the first time, and successfully predicted a series of important anomalous effects, which received extensive international experimental validation and positive evaluations, including Nobel Prize winners.
In 2006, Jiang Lan set up the first domestic scientific research team of femtosecond laser manufacturing and its application in BeiJing.
At that time, what stood in front of the team was another obstacle. The "inherent defects" of femtosecond laser processing, such as low efficiency, accuracy worse than the diffraction limit, and low depth-to-diameter ratio, are the reasons why femtosecond laser processing has not been applied in practice for more than 20 years.
Jiang Lan applied the model he established to reveal that to solve the above problems, the core is "whether it is possible to regulate the local transient electron dynamics". According to his theoretical model prediction, Jiang Lan proposed that the femtosecond laser space-time shaping can be realized through the laser manufacturing of local transient electronic dynamics of the active control, and then control the processing results of the technical route. This technical route significantly expands the limit capabilities of laser fabrication. Under the support of this theoretical model, Jiang Lan's team improved the efficiency of femtosecond laser processing by 56 times, repeatable processing accuracy of 1/14 of the wavelength, and the limit of depth-to-diameter ratio from 20:1 to more than 5000:1.
Later, Jiang Lan proposed and led his team to develop a cross-scale quasi-3D ultrafast continuous observation system. "Across 15 time orders of magnitude, the peak frame rate of trillions of frames per second of the observation system to verify the femtosecond laser electron dynamics modulation manufacturing new principles." Jiang Lan said.
In the national "13th Five-Year" scientific and technological innovation exhibition, Jiang Lan team's femtosecond laser electron dynamic control manufacturing results selected. 11 academicians composed of the appraisal committee commented that: "the first to achieve the laser manufacturing of the electronic level of active control and femtosecond laser processing of industrialization and major engineering Application ...... overall reached the international leading level."
A layman walking into the femtosecond laser micro-nano manufacturing research room, it is difficult to connect the large-scale experimental equipment in front of you as well as the hundreds of optical lenses lined up on the workbench with real life. But the researchers who have broken through the basic scientific research have seen the extremely broad application prospects.
Cell phone screen shaped cutting is a key technology for cell phone manufacturing. "The structure of a cell phone screen is like a multi-layer cake, in different layers were distributed with glass, polymer, metal, insulator, and glue." Jiang Lan said, "the traditional tool can not do anything about the place, it is the femtosecond laser show their hands." At present, the application of Jiang Lan proposed electronic dynamic control cutting process, and the large laser research and development of femtosecond laser manufacturing equipment in the global market share of 60%.
Three-dimensional complex microstructure processing of difficult-to-process materials is a world-class problem in the field of cutting-edge manufacturing. Jiang Lan invented the electronic dynamic adjustment control hole, cutting, leveling, engraving and other new technologies, led his team to develop a series of major indicators significantly better than the international level of new equipment, for the 37 national major scientific and technological projects and major national equipment to lay the cornerstone.
Jiang Lan said: "A strong manufacturing industry is the cornerstone of the construction of a strong country, and a strong manufacturing industry is often ahead of the establishment of the status of a strong country for 20 years."
During the "12th Five-Year Plan" period, high-energy beam manufacturing has become a key support direction of the National Natural Science Foundation of China (NSFC), and Jiang Lan served as the person in charge of the field of high-energy beams and special energy field manufacturing, and led the writing of a series of planning for the field of high-energy beams and special energy fields in the NSFC since the "12th Five-Year Plan". Planning.
During the "13th Five-Year Plan" and "14th Five-Year Plan" period, Mr. Jiang Lan served as the head of the expert group for the preparation of the implementation plan of the "Additive Manufacturing and Laser Manufacturing" key special project of the National Key Research and Development Program (NKRDP), as well as the head of the expert group and the general expert group for the preparation of the guidebook. Jiang Lan served as the head of the expert group for the preparation of the implementation plan, guidelines and overall expert group of the National Key R&D Program "Additive Manufacturing and Laser Manufacturing". He invested a lot of time in the first national key project in advanced manufacturing. At present, the special project has deployed 112 related R & D projects, which has strongly promoted China's additive manufacturing and laser manufacturing among the first echelon of the international community.
Zhang Xueqiang, who has been working at the institute for two years, still remembers listening to Jiang Lan's lecture at the University of California, Berkeley. "He talked about the technological progress of femtosecond laser manufacturing, and also the potential application prospects of femtosecond laser manufacturing." Xueqiang Zhang said, "After the lecture, when we exchanged ideas, he asked me 'if I would like to do some real scientific research together,' and that one sentence called me back."
Students in Jiang Lan's technical team know that Mr. Jiang is against publishing "water articles". Lian Yiling, a doctoral student, explained, "The experiments done by other people, come back to reproduce, and then adjust the parameters; or other people's experiments, change a kind of material and do it again, are 'water articles'."
What is the real scientific research? Jiang Lan said, "Either make breakthroughs in the academic frontier to go to the top of the sky, expanding the field of human cognition; or in the major national needs and the main battlefield of the national economy to realize the application to go to the ground, to overcome the key technical problems."
Strict requirements have brought out a tough scientific research echelon. Jiang Lan has trained 33 PhDs and postdoctoral fellows, 40% of whom are teaching in "double first-class" universities and 57% of whom are working in national key industry-related research institutes. The doctoral students under his supervision have won the "Shangyin Excellent Mechanical Doctoral Dissertation Award" of the Chinese Mechanical Engineering Society for six times, including silver, bronze, excellent and best work awards, and the grand prize of the "Challenge Cup" national competition, etc., and two of them have been approved as the European Union's "Marie Curie" and "Marie Curie" researchers. Two of them have been recognized as "Marie Curie" scholars of the European Union. So far, Jiang Lan has trained 9 national high-level talents.
In the Institute of Femtosecond Laser Micro-Nano Manufacturing of BeiJing, there are still breakthroughs in the application field of femtosecond laser. Prof. Li Xiaowei is working on a series of major applications of femtosecond laser manufacturing. Prof. Jie Hu is focusing on medical-industrial fusion, and femtosecond laser technology can provide antibacterial, anticoagulant and drug-carrying medical devices for bone tumor treatment. Prof. Li Xin is focusing on the application of composite processing in aerospace.
In Jiang Lan's opinion, the invulnerability of femtosecond lasers should also be a characteristic of a team that aspires to real scientific research. "Aiming at the frontiers of science and technology and serving the needs of the country, this is the mission of the times for our generation of scientific researchers, and also the secret of the breakthroughs we continue to make in our work." Jiang Lan said.
