According to Optica magazine, HUST has made a breakthrough in the field of free-form beam modulation.
Optica published online the research paper "Sculpting Optical Fields into Caustic Patterns based on Freeform Optics" by Associate Professor Ma Donglin's group at the School of Optoelectronic Information of Huazhong University of Science and Technology (HUST). " research paper.
Manipulating the energy transfer of optical fields is an important topic in optics research, and has a wide range of applications in laser micromachining, optical tweezers, optical micro-imaging, illumination engineering and other fields. Scattering phenomenon is a natural process of regulating light energy transfer that exists in nature and daily life, such as sunlight irradiation of flowing water forms a ripple-like pattern on the bottom of the water (Fig. 1a), and the formation of a spiky light spot inside a glass of water under the light (Fig. 1b), and so on. These phenomena show that common optical surfaces and media in life have a focusing effect on light, forming sharp and stable spot patterns.
Fig. (a) Bijective-mapping-based freeform optics design. (b) Design of caustic patterns enabling new functions of freeform optical elements (FOEs).
Fig. 1. Modulation of optical energy transmission based on the defocusing phenomenon
In recent years, there has been a booming research in the field of optical design on freeform optical elements, which have the advantages of high modulation accuracy and high energy efficiency, and are suitable for the problem of beam modulation at macroscopic sizes. However, the existing design mechanisms are mainly based on partial differential equations to solve the coordinates of the light target position or the free-form surface point cloud, which are unable to deal with the emergence of astigmatism, and the modulation problem of the light flux transfer in three-dimensional space is not well studied.
Ma Donglin team proposed a freeform optics (freeform optics) design scheme, breaking the traditional freeform light regulation design limitations, no longer require a single plane using a complete light beam to achieve the prescribed light distribution, and break through the incident light and target intersection between the double shot mapping relationship, through the incident light light energy to accurately focus and regulate, and to achieve any form of sharp astigmatic light spot (Fig. 1c). The method can also propagate the peak light field intensity along a prescribed spatial trajectory by focusing the light on a simple three-dimensional curve, which is expected to apply free-form surface elements to a wider range of light modulation applications.
To validate the performance of such free-form surface elements, the team performed a comparison with a design method based on bijection mapping. By projecting to a spatial light modulator, four different sizes of spot distributions were generated, respectively. The results showed that the scattering-based design was able to form sharper patterns compared to the conventional design.
Figure 2. Comparison of design results with traditional methods
The research team also verified other potentials of the defocusing-based design, such as the modulation of Lambertian point light source luminescence and beam shaping in three-dimensional space, and some of the design results are shown in Figures 3 and 4.
Figure 3. Free-form surface illumination element realizing a diffuse focus pattern
Figure 4. Extending the depth of field of light distribution
Shili Wei, a PhD student at the School of Optoelectronic Information of Huazhong University of Science and Technology, is the first author of the paper, Associate Professor Donglin Ma is the corresponding author, and PhD student Yitong Li is the co-author. The work was funded by the National Natural Science Foundation of China and the Shenzhen Natural Science Foundation.
According to the secretariat of the Yangtze River Delta G60 Laser Alliance, Donglin Ma received funding from the China Scholarship Council (CSC) in 2010 to pursue a Master of Science in Optical Engineering and a Doctor of Science in the College of Optical Science at the University of Arizona, one of the three major optical centers in the United States. During his Ph.D. period, he devoted himself to the research of illumination engineering, free-form optical design, related optical system development, and optical testing, and achieved fruitful results, accomplished a number of research projects, published or presented several academic papers and conference papers, and his related work has been publicly reported by Laser Focus World and other media, and he has developed the CGH interferometry, panorama endoscopic system, microscope, and optical test system. endoscopy system, microscope, 3D measuring instrument and many other optical systems. After obtaining his Ph.D. degree, he returned to China full-time in 2016, and is currently working as an associate professor in the School of Optics and Electronic Information of Huazhong University of Science and Technology. During this period, he served as a technical advisor to the Scientific Committee of the "Large (12-meter) Optical Infrared Telescope", a major project in China's 13th Five-Year Plan, where he was responsible for evaluating the optical design of the telescope in the preliminary work of the project on the one hand, and was the main person in charge of the conceptual design of the telescope in the competition of Huazhong University of Science and Technology (HUST) on the other hand. The design of the telescope based on large optical infrared telescope has been reported by Science, a famous American science and technology magazine, and has also attracted great attention from the domestic media, including intellectuals. My academic research work adhering to the Huazhong University of Science and Technology's academic style requirements, seriously write two "papers", one in the academic journals, has published more than 30 academic papers, applied for a number of invention patents; the other is written in the motherland, undertook a number of national and provincial level vertical projects, military vertical and civilian port He has undertaken a number of national and provincial vertical projects, military vertical and civilian horizontal projects, etc., which have achieved important social impact.
At present, he is mainly responsible for three aspects of scientific research work: first, to promote the establishment and construction of the major scientific device "Nantian Spectroscopic Survey Telescope", as well as the core key technology research work, the total construction budget of the project is expected to reach about 1.2 billion; second, to take the lead in undertaking the research work of the military 863 project of the laser special sub-topics, including membrane system stability, new types of lasers, and the research work of the laser project. Secondly, he is mainly responsible for the research of a series of sub-topics of the 863 project on laser, including membrane system stability, new laser lighting system, sodium guide star laser transmitter, etc. Thirdly, he is mainly responsible for the research and development of Tianqin telescope, which is the core device of the Tianqin Project.
