摘要
艾里光因其自加速、无衍射和自修复的特性,在多个领域中得到了广泛应用。飞秒激光双光子加工技术以其灵活的三维高精度加工能力,常用于各类微器件的高精密制备。将飞秒激光双光子聚合技术与自加速光场相结合,有助于推动此技术的发展并拓宽其应用范围。从艾里光的生成与应用需求出发,利用空间光调制器直接生成对称的艾里光束。通过结合动态全息加工技术,实现了三维多瓣“花朵”结构的快速加工。同时,通过引入自组装技术,实现了“张闭可控”的三维微型花朵阵列的高效制备。最后,将动态全息与三维移动台的运动相结合,实现了多参数灵活调控的复合运动加工。在保证加工精度的同时,进一步提升了设计和加工的灵活性。
Objective The femtosecond laser twophoton processing technology,known for its flexible threedimensional(3D)highprecision machining capabilities,is commonly employed for the highprecision fabrication of various microdevices.However,existing singlepoint scanning strategies exhibit low processing efficiency,which significantly limits further development of this technology.To address this issue,researchers have proposed several parallel processing techniques,including those based on microlens arrays,diffractive optical elements,and multibeam interference methods.Although these methods demonstrate certain advantages in improving the processing efficiency,they still possess some significant limitations.Liquid crystal on silicon spatial light modulators(LCoSSLMs)can freely modulate the wavefront of a beam,enabling the generation of multifoci arrays and various structured lights.The combination of spatial lightshaping technology with femtosecond laser twophoton polymerization can effectively enhance both the processing efficiency and flexibility.Airy beams have been widely applied across multiple fields owing to their selfaccelerating,nondiffraction,and selfhealing characteristics.In a previous study,two symmetric Airy beams were directly generated using LCoSSLM,achieving the efficient fabrication of 3D microgripper structures via a single exposure.Building upon this foundation,this study integrates dynamic holographic processing technology with femtosecond laser twophoton polymerization to further enhance the processing efficiency and flexibility,advance the development of twophoton processing technology,and broaden its application scope.Methods The femtosecond laser source used in this study is a modelocked Ti∶sapphire ultrafast oscillator with key parameters,including a central wavelength of 800 nm,pulse width of 75 fs,and repetition frequency of 80 MHz.After passing through the expansion system,the laser beam is directed onto the LCoSSLM using a grazing incidence technique with mirrors.Mechanical shutters and power attenuators are employed to control the on/off states and power levels of the laser,respectively.Computergenerated dynamic holograms are loaded onto the LCoSSLM to modulate the wavefront distribution of the laser light.The modulated laser then sequentially passes through two lenses with focal lengths of 600 mm and 200 mm.The conjugate focal planes of the two lenses form a 4f system for spatial filtering and beam reduction.Finally,a microscope objective lens focuses the laser for processing.The 3D piezoelectric stage supports the sample and offers highprecision motion control,with a coaxial charge coupled device(CCD)employed for realtime imaging and monitoring of the entire processing procedure.The reflective LCoSSLM used has a resolution of 1920 pixel×1080 pixel with a pixel pitch of 8μm.Each pixel can independently modulate the wavefront of the beam within its area,with a modulation grayscale range from 0 to 255,corresponding to a phase range from 0 to 2π.MATLAB software is used to generate computergenerated holograms,which are then compiled into graphic interchange format(GIF)dynamic images.The 3D piezoelectric stage has a movement range of 200μm×200μm×200μm,with a positioning accuracy of less than 1 nm and repeatability of less than 5 nm,ensuring the precision and stability of micronano processing.The objective lens employed in the experiments is a 60×oil immersion lens,with a numerical aperture(NA)of 1.35.A commercially available negative photoresist is used.Results and Discussions The directly generated symmetric Airy beam holograms are rotated to create a GIF dynamic image,which is then loaded onto the LCoSSLM.With the laser power set to 70 mW,the rotation angle can be controlled by adjusting the exposure time,resulting in bowlshaped structures with varying aperture sizes(Fig.5).By dynamically and holographically processing multiple symmetric Airy beams with different parameters,microflowers are rapidly fabricated by adjusting the exposure time,with an eightpetal flower requiring only 1.4 s for processing.The advantage of dynamic holographic processing is its ability to rapidly realize complex 3D structures without relying on the motion conditions of the 3D moving stage,thereby effectively reducing the equipment costs of the experimental system.Furthermore,“openclose controllable”3D microflower fabrication is achieved by integrating selfassembly techniques and appropriately controlling processing parameters(Fig.6).Finally,a composite motion processing technology that combines dynamic holography with a 3D moving stage is proposed.By utilizing the dynamic holographic technique of Airy beams,along with the horizontal movement of the stage,microspring structures with varying numbers of turns are rapidly processed.Annular structures with different petal counts are fabricated by altering the motion of the moving stage to a circular motion and adjusting the radius of this motion(Fig.8).The combination of 3D optical field dynamic holography and moving stage motion methods provides various options for designing 3D structures,thereby enhancing both design flexibility and processing diversity.Conclusions This paper presents a composite processing technology that integrates dynamic holography with the motion of a 3D moving platform.By rotating the hologram,dynamic holography enables the rapid fabrication of 3D multipetal“flower”structures.Furthermore,by incorporating capillary selfassembly techniques,the“opening”and“closing”of these flowers can be controlled.Through the dynamic variation of the hologram and realtime motion of the 3D moving platform,3D microspring structures are efficiently fabricated.This technology offers a high processing efficiency and fabrication flexibility,supporting the precise manufacturing of complex structures over large areas.In the future,the possibility of singleexposure fabrication of arbitrary 3D structures can be explored based on dynamic femtosecond laser holographic processing technology.In addition,combining 3D structured light fields with iterative computational holography has the potential to enhance femtosecond laser processing technology,effectively improving both processing efficiency and flexibility.
作者
桂新煜
蔡泽
汪超炜
张乐然
胡衍雷
吴东**
Gui Xinyu;Cai Ze;Wang Chaowei;Zhang Leran;Hu Yanlei;Wu Dong(School of Engineering Science,University of Science and Technology of China,Hefei 230026,Anhui,China)
出处
《中国激光》
北大核心
2025年第8期233-241,共9页
Chinese Journal of Lasers
基金
科技部国家重点研发计划(2021YFF0502700,2024YFB4610700)
国家自然科学基金(52375582,62475252)。
关键词
飞秒激光
艾里光束
动态全息加工
双光子聚合
三维多瓣结构
femtosecond laser
Airy beams
dynamic holographic processing
twophoton polymerization
3D multipetal structures
