Electrons dynamics control micro-hole drilling using temporally/spatially shaped femtosecond laser

Zhang Chao; Li Min; Ye Baichen; Wu Jianying; Wang Zhi; Li Xiaowei

doi:10.12086/oee.2022.210389

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Zhang C, Li M, Ye B C, et al. Electrons dynamics control micro-hole drilling using temporally/spatially shaped femtosecond laser[J]. Opto-Electron Eng, 2022, 49(2): 210389. doi: 10.12086/oee.2022.210389

Citation:

Zhang C, Li M, Ye B C, et al. Electrons dynamics control micro-hole drilling using temporally/spatially shaped femtosecond laser[J]. Opto-Electron Eng, 2022, 49(2): 210389. doi: 10.12086/oee.2022.210389

Electrons dynamics control micro-hole drilling using temporally/spatially shaped femtosecond laser

Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China

Fund Project: National Natural Science Foundation of China (NSFC) (52075041), Beijing Municipal Natural Science Foundation (JQ20015), and Beijing Outstanding Young Scientist Program (BJJWZYJH01201910007022)

More Information

^*Corresponding author: lixiaowei@bit.edu.cn

Received Date 03 December 2021

Revised Date 09 February 2022

Published Date 25 February 2022

Abstract

Abstract

As a common structure, microholes are widely used in various fields, including biomedical, aerospace, 3D packaging and so on. Femtosecond laser has unique advantages in drilling high-quality microhole due to its ultra-short pulse duration and ultra-high peak power. This review covers temporally/spatially shaped femtosecond laser microhole drilling methods and their applications over the past decade, including femtosecond laser temporally/spatially shaped methods, temporally/spatially shaped femtosecond laser microhole drilling based on electrons dynamics control, and the applications of microhole in transmittance enhancement and anti-reflection, material cutting, oil/water separation, fog collection and gas collection. Furthermore, present challenges and future research opportunities in this field are analyzed.
- femtosecond laser /
- electrons dynamic control /
- micro-hole drilling /
- temporally/spatially shaping /
- micro-hole applications

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References

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Overview

Overview

As a common structure, microholes are widely used in biomedical, microfluidic devices, aerospace and 3D packaging fields. As the performance requirements of various functional devices are more and more strict in practical applications, the requirements for the quality and depth-diameter ratio of microhole processing also become much higher, which makes the microhole processing in manufacturing extremely challenging. In view of the increasingly strict requirements of microhole indicators, selecting a suitable microhole processing method is the key.

At present, the commonly used microhole drilling methods are mechanical drilling, electric spark drilling, electron beam drilling, focused ion beam drilling, laser drilling and electro discharge machining (EDM). Mechanical drilling is easy to operate, but it is difficult to process microholes with small diameters and high depth-diameter ratios. EDM drilling is only suitable for conductive materials and is difficult to process. Electron beam and focused ion beam drilling can achieve micro holes with nanometer to submicron precision, but the conditions are harsh. The equipment is expensive, and the processing efficiency is slow. Laser drilling has the characteristics of non-contact, wide material adaptability and high processing efficiency, but the microholes processed by continuous laser and long pulse laser have a certain heat affected zone.

Femtosecond laser is different from the continuous laser and long pulse laser. It has characteristics of ultra-short pulse duration and ultra-high peak power, enabling high-quality processing capacity and wide material adaptability. Compared with traditional processing methods, femtosecond laser has the following three significant advantages: (1) Small thermal effect and high processing quality; (2) Strong nonlinear effect, wide range of material processing and higher processing resolution; (3) The "true" 3D processing. When the femtosecond laser is focused inside the transparent medium, only the material near the focal point can be modified or removed, so the "true" 3D machining of arbitrary complex structures can be achieved with femtosecond laser. Therefore, femtosecond laser provides a new possibility for high-quality microhole drilling. Unshaped Gaussian laser microhole drilling has the contradiction between small diameters and high depth-diameter ratios. Due to the precise and adjustable properties of femtosecond laser, its light field distribution can be controlled in terms of transient local electronic dynamic and subsequent phase transitions by temporally/spatially shaping. In this way, the microhole can be drilled to satisfy the requirements of both small diameter and high depth-diameter ratio.

In this paper, the processing methods regarding electrons dynamics control micro-hole drilling using temporally/spatially shaped femtosecond laser and the applications of microholes in transmittance enhancement and anti-reflection, material cutting, oil and water separation, fog collection and gas transportation are reviewed.