1 3 DOI 10.1007/s00340-015-6011-6 Appl. Phys. B Holographic laser sweeper for in-process debris removal Kazuki Sakuma · Satoshi Hasegawa · Hidetomo Takahashi · Michiharu Ota · Yoshio Hayasaki Received: 11 September 2014 / Accepted: 9 January 2015 © Springer-Verlag Berlin Heidelberg 2015 processing. In particular, there are increasing demands for reducing the amount debris in high-precision ultrashort- pulse laser processing. To reduce the amount of debris and the size of the region in which the debris is scattered, laser processing has been performed in a special gas [1] and liq- uid [2], and also with a transparent material coating [3]. Electrostatic collection of debris has also been reported [4]. The general method for reducing the amount of debris is to wash it away with water or a special solvent. These meth- ods have been successfully used in a number of studies. However, in order to achieve high throughput and reduced costs, it is desirable to perform material processing in a dry process without the need for additional special processes. Laser cleaning without any additional special equipment or special treatment of the target material has been studied with a variety of lasers and a variety of materials. Laser cleaning has been performed as a post-processing step after laser fabrication using short-pulse lasers [5, 6], excimer lasers [7–9], CO 2 lasers [10, 11], an ultraviolet nanosec- ond pulse laser [12], and a frequency-doubled Q-switched Nd:YAG laser [13, 14]. Laser cleaning has also been dem- onstrated using a liquid-assisted technique [15] and acous- tic waves induced by focused pulsed laser irradiation [16, 17]. Here, we propose a laser cleaning method whose novelty is the use of a shaped beam generated with a holographic laser processing technique [18–20] as a cleaning beam. In addition, the cleaning beam is radiated onto the target material together with a processing beam; in other words, the laser cleaning is performed during laser processing. A line-focused beam was radiated onto a laser process- ing target material to sweep away the debris generated by laser ablation. The laser processing setup for debris sweep- ing had a simple and practical configuration composed of beam transmission optics from a laser source to the target Abstract Debris deposited around laser-processed struc- tures is a critical issue in high-precision laser processing and should be removed. We demonstrated a new debris removal method that is performed during laser processing. A line-focused beam that is radiated onto a target material simultaneously with a processing beam sweeps away the debris generated by laser ablation. Two physical processes are involved: One is direct photon excitation of the attached debris, similar to laser ablation, due to a smaller ablation threshold of the debris, and the other is blowing away the debris with a laser-induced pressure wave. The laser pro- cessing setup for debris sweeping has a simple and prac- tical configuration composed of beam transmission optics from a laser source to the target and a spatial light modu- lator that displays a computer-generated hologram. This in-process debris removal method has the advantages of needing no additional equipment other than the optics, no additional operations, no special materials, and no specific operating environment. 1 Introduction Control of debris in micro- and nano-laser material pro- cessing, which is performed to remove scattered materi- als from an ablation point before they become attached to the target surface, as well as to remove already attached debris, is very important for achieving high-quality laser K. Sakuma · S. Hasegawa · Y. Hayasaki (*) Center for Optical Research and Education (CORE), Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585, Japan e-mail: hayasaki@opt.utsunomiya-u.ac.jp H. Takahashi · M. Ota Aisin Seiki Co., Ltd, 2-1 Asahi-machi, Kariya 448-8650, Japan