2024年4月25日にパシフィコ横浜で開催されるレーザー加工に関する国際会議SLPC2024にて、M2峯邑康志君がポスター発表を行います。

タイトル：Investigation of fs-LIPSS on sapphire suitable for anti-reflection property

著者：Yasushi Minemura and Godai Miyaji

ポスター番号：SLPCp-23

発表日：2024年4月25日 10:30-12:00

場所：パシフィコ横浜

概要：We have investigated the reflectivity at sapphire surfaces with fs-LIPSSs by using an RCWA method. The result clearly shows that the surface with sinusoidal nanostructures of ≦250 nm in period can strongly reduce the reflectivity.

2024年3月28日に、電気学会 光・量子デバイス研究会（ミライエ長岡およびWeb、テーマ「次世代レーザプロセシング技術」）にて、宮地研が関わる研究成果を2件発表しました。

[OQD-24-003] 透明フッ素樹脂CYTOP製3次元マイクロ流体チップの作製と高解像度細胞観察

◎半澤未来（理化学研究所/東京農工大学）, 小幡孝太郎（理化学研究所）, シマフェリックス（National Institute for Laser, Plasma and Radiation Physics）, 河野弘幸, 戸島拓郎, 宮代大輔, 尾笹一成（理化学研究所）, 花田修賢（弘前大学）, 中野明彦（理化学研究所）, 宮地悟代（東京農工大学）, 宮脇敦史, 杉岡幸次（理化学研究所）

[OQD-24-006] 均一なナノ周期構造の形成に向けたフェムト秒レーザーのトップハットビームへの整形と2光束干渉

◎住本武優, 宮地悟代（東京農工大学）

2024年3月22,23日に、第71回応用物理学会春季学術講演会（東京都市大）にて、宮地研が関わる研究成果を５件発表いたしました。

3/22(金) 9:30-9:45 [22a-13M-1]

フェムト秒レーザー二光束干渉法によるZnO基板への均一LIPSSの形成

〇森本 純至1,2、白 石1、小幡 孝太郎1、中田 芳樹3、宮地 悟代2、杉岡 幸次1 (1.理研　光量 子、2.農工大、3.大阪大)

3/23(土) 11:45-12:00 [23a-13M-11]

透明フッ素樹脂材料CYTOP内への３次元ナノチャネル作製に向けた加工分解能の改善

〇半澤 未来1,2、小幡 孝太郎1、シマ フェリックス1,3、河野 弘幸1,4、尾笹 一成1、花田 修賢 5、宮地 悟代2、宮脇 敦史1,4、杉岡 幸次1 (1.理研 光量子、2.東京農工大、3.INFLPR、4.理研 CBS、5.弘前大理工)

3/23(土) 14:15-14:30 [23p-12B-4]

周期構造基板上光捕捉におけるマイクロ粒子の光軸に沿った移動現象

〇吉川 瑞紀1、涔澤 諒1、門屋 祥太郎1、道畑 正岐1、小玉 脩平2、宮地 悟代3、高橋 哲1 (1.東 京大工、2.東京都市大理工、3.東京農工大工)

3/23(土) 14:30-14:45 [23p-13M-5]

円偏光GHzバーストモードフェムト秒レーザーによるTi表面へのテトラポット様表面微細構造 の形成

〇川端 祥太1,2、白 石1、小幡 孝太郎1、尾笹 一成1、宮地 悟代2、杉岡 幸次1 (1.理研　光量 子、2.農工大)

3/23(土) 16:00-16:15 [23p-13M-10]

GHzバーストモードフェムト秒レーザーパルスを用いたLIPAAによるサファイアの高品質微細 穴加工

〇小幡 孝太郎1、川端 祥太1,2、花田 修賢3、宮地 悟代2、杉岡 幸次1 (1.理研 光量子、2.東京 農工大、3.弘前大理工)

2024年3月18日に東京都立産業貿易センターで開催されるレーザ加工学会 第100回記念講演会にて、宮地がポスター発表を行いました。

タイトル：ガラス表面に形成したフェムト秒レーザ誘起ナノ周期構造による透過光強度上昇

著者：三善武碩1,2, 高田英行2, 吉富大2, 奈良崎愛子2, 宮地悟代1*（1東京農工大，2産総研）

ポスター番号：P23

発表日：2024年3月18日

場所：東京都立産業貿易センター浜松町館

2024年5月5-10日に、ノースキャロライナ（アメリカ）で開催されるCLEO2024にて宮地が招待講演を行います。数サイクル7fsレーザーパルスによる微細構造形成とその物理過程について話します。

Session: A&T 2: Laser-based Manufacturing, Machining and Nanoprinting

Paper title: Fine-periodic nanostructure formation on solids with few-cycle femtosecond laser pulses

Paper authors: Godai Miyaji*, Yuto Iida, Seiya Nikaido, and Akihiro Ishihara

*corresponding author

下の写真は実験装置の一部。

Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXVIII および Laser-based Micro- and Nanoprocessing (LBMP) XVIII in SPIE. Photonics West 2024（サンフランシスコ、アメリカ）にて、宮地研が関わる研究成果を5件発表いたしました。

LAMOM

[12872-20] Oral presentation

Fabrication of 3D CYTOP biochip using two-photon polymerized mold towards super-resolution bioimaging

Author(s): Mirai Hanzawa, Tokyo Univ. of Agriculture and Technology (Japan), RIKEN Ctr. for Advanced Photonics (Japan); Kotaro Obata, RIKEN Ctr. for Advanced Photonics (Japan); Felix Sima, CETAL, Institutul National pentru Fizica Laserilor, Plasmei si Radiatiei (Romania), RIKEN Ctr. for Advanced Photonics (Japan); Hiroyuki Kawano, RIKEN Ctr. for Brain Science (Japan), RIKEN Ctr. for Advanced Photonics (Japan); Kazunari Ozasa, RIKEN Ctr. for Advanced Photonics (Japan); Yasutaka Hanada, Hirosaki Univ. (Japan); Godai Miyaji, Tokyo Univ. of Agriculture and Technology (Japan); Atsushi Miyawaki, RIKEN Ctr. for Brain Science (Japan), RIKEN Ctr. for Advanced Photonics (Japan); Koji Sugioka, RIKEN Ctr. for Advanced Photonics (Japan)

30 January 2024 • 2:35 PM - 2:55 PM PST | Moscone Center, Room 215 (Level 2 South)

As a platform for high resolution bioimaging, biochips with a refractive index very close to that of a culture medium (water) are highly demanded. CYTOP (AGC Corporation) is a promising material, since its refractive index (1.34) is almost similar to that of water (1.33). However, high transparency in also the ultraviolet region and high chemical resistance of CYTOP make it difficult to fabricate 3D microstructures for biochips. In this study we present fabrication method of 3D biochips based on CYTOP for cell observation by the molding process using 3D micro/nanostructures fabricated by two-photon polymerization with femtosecond laser.

[12872-35] Poster Presentation

Enhancement of transmitted light from femtosecond-laser-induced periodic nanostructure on glass

Author(s): Takemichi Miyoshi, Tokyo Univ. of Agriculture and Technology (Japan), National Institute of Advanced Industrial Science and Technology (Japan); Hideyuki Takada, Dai Yoshitomi, Aiko Narazaki, National Institute of Advanced Industrial Science and Technology (Japan); Godai Miyaji, Tokyo Univ. of Agriculture and Technology (Japan)

30 January 2024 • 6:00 PM - 8:00 PM PST | Moscone Center, Room 2003 (Level 2 West)

To identify the formation of periodic nanostructures induced by superimposed multiple shots of femtosecond laser pulses on transparent materials, we developed a novel in-process monitoring technique by observing the reflectivity and the transmittance of the surface. The transmittance at the glass surface having the line-like periodic nanostructures with a period of ~200 nm and a depth of ~1 μm achieved 200% in the center of the ablation trace. By simulating the time-dependent electromagnetic-field distribution of the illumination light passing through the nanostructured surface, the high transmittance can be attributed to anti-reflection and lens effects induced by a low refractive index with the nanostructured surface.

LBMP

[12873-12] Oral presentation

Formation and characterization of 2D-LIPSS on Ti surfaces with GHz burst mode femtosecond laser pulses

Author(s): Shota Kawabata, Tokyo Univ. of Agriculture and Technology (Japan), RIKEN Ctr. for Advanced Photonics (Japan); Felix Sima, Institutul National pentru Fizica Laserilor, Plasmei si Radiatiei (Romania), RIKEN Ctr. for Advanced Photonics (Japan); Shi Bai, Kazunari Ozasa, Kotaro Obata, RIKEN Ctr. for Advanced Photonics (Japan); Godai Miyaji, Tokyo Univ. of Agriculture and Technology (Japan); Koji Sugioka, RIKEN Ctr. for Advanced Photonics (Japan)

30 January 2024 • 11:10 AM - 11:30 AM PST | Moscone Center, Room 214 (Level 2 South)

The GHz burst mode femtosecond (fs) laser pulses have attracted considerable attention because they can perform better quality and higher efficiency ablation compared to the conventional irradiation scheme of fs pulses (single-pulse mode). Recently, we have demonstrated that the GHz burst mode fs laser pulses can create two-dimensional (2D) periodic surface structures (LIPSS) on Si surfaces. In this paper, we extend the GHz burst mode fs laser processing to form LIPSS on Ti plates. Our aim was to further investigate the more detailed mechanism and explore practical applications. Although the material characteristics of Ti are significantly different from Si, the GHz burst mode fs laser pulses can also create 2D-LIPSS. Then, mesenchymal stem cells cultured on the formed 2D-LIPSS were found to exhibit different behavior on 1D-LIPSS as compared with bare Ti surfaces.

[12873-80] Poster presentation

Formation of homogeneous LIPSS on ZnO by two-beam interference of femtosecond laser pulses

Author(s): Junji Morimoto, Tokyo Univ. of Agriculture and Technology (Japan), RIKEN Ctr. for Advanced Photonics (Japan); Shi Bai, Kotaro Obata, RIKEN Ctr. for Advanced Photonics (Japan); Godai Miyaji, Tokyo Univ. of Agriculture and Technology (Japan); Koji Sugioka, RIKEN Ctr. for Advanced Photonics (Japan)

30 January 2024 • 6:00 PM - 8:00 PM PST | Moscone Center, Room 2003 (Level 2 West)

Irradiation of femtosecond laser pulses at laser fluence near ablation threshold triggers formation of laser-induced periodic surface structures (LIPSS). The formed LIPSS is, however, usually spatially inhomogeneous. Homogeneous LIPSS are preferred for many applications. We have reported that a single nanogroove can be formed by precisely controlling the laser fluence. Based on this result, single nano grooves were able to be formed at the centers of some fringes formed by two-beam interference of femtosecond laser pulses. The formed single nanogrooves acted as a seed to create homogeneous LIPSS in a large area by scanning the laser beams.

Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXIV

[12875-25] Invited talk

Data-driven ultrashort pulse laser processing using deep neural network for shape prediction and in-process monitoring (Invited Paper)

Authors: Dai Yoshitomi, National Institute of Advanced Industrial Science and Technology (Japan), Hideyuki Takada, National Institute of Advanced Industrial Science and Technology (Japan), Takemichi Miyoshi, Tokyo Univ. of Agriculture and Technology (Japan), National Institute of Advanced Industrial Science and Technology (Japan), Daisuke Nagai, Tokyo Univ. of Agriculture and Technology (Japan), National Institute of Advanced Industrial Science and Technology (Japan), Godai Miyaji, Tokyo Univ. of Agriculture and Technology (Japan), Aiko Narazaki, National Institute of Advanced Industrial Science and Technology (Japan)

29 January 2024 • 10:30 AM - 11:00 AM PST | Moscone Center, Room 52 (Lower Mezzanine South)

We report on recent research on the development of data-driven ultrashort pulse laser processing to achieve higher productivity and quality. We are developing in-process monitoring, artificial intelligence (AI) optimization, and fast active control of the laser based on them. These key technologies are introduced for micro-drilling of metals and transparent materials and laser-induced periodic surface structure (LIPSS) formation on a silica glass. We demonstrate a fast pulse-to-pulse modulation of the fluences to control the ablation efficiency. A deep neural network was utilized to predict the 3-dimensional shapes of the ablation craters depending on the laser parameters (fluence and pulse duration). The scheme was extended to 10 sequential modulations of fluences. An in-process monitoring of the crack formation on glasses was implemented by optical transmission imaging with deep neural network. The optical reflection/transmission technique was also employed to probe the quality of the LIPSS formation on a silica glass.

2024年1月17日(水)に、レーザー学会学術講演会 第44回年次大会のシンポジウムにて、宮地が招待講演を行いました。

シンポジウムタイトル：[S07] イノベイティブなレーザー加工技術の社会実装

講演タイトル：[S07-17p-VIII-02] フェムト秒レーザー励起表面プラズモンを利用した微細加工技術の基礎

2024年1月18日に日本科学未来館で開催されるレーザー学会学術講演会 第44回年次大会にて、三善武碩（B4）がポスター発表を行います。

[P01-18p-P-16] 

フェムト秒レーザーによってガラス表面に形成した周期ナノ構造による透過光強度上昇

*三善 武碩1,2、高田 英行2、吉富 大2、奈良崎 愛子2、宮地 悟代1 (1. 東京農工大、2. 産総研)

2023年12月4日に、4th International Conference on Optics, Photonics, and Lasers (OPL-2023)にて、宮地が招待講演を行いました。

場所：Sheraton Grand Hotel Hiroshima, 広島, 日本

発表タイトル：Direct Surface Nanopatterning with Intense Femtosecond-Laser-Induced Plasmonic Near-Fields

宮地研が関連する研究成果が発表されました。

掲載論文情報

掲載誌：Frontiers in Nanotechnology

出版日：2023年11月20日付（電子版）

論文名：Formation of two-dimensional laser-induced periodic surface structures on titanium by GHz burst mode femtosecond laser pulses

著者名：Shota Kawabata, Shi Bai, Kotaro Obata, Kazunari Ozasa, Godai Miyaji, and Koji Sugioka*

DOI　：https://10.3389/fnano.2023.1267284

GHz burst mode femtosecond (fs) laser pulses, which consist of a series of pulse trains with ultra-fast intervals of several hundred picoseconds, have offered distinct features for material processing compared to conventional irradiation of laser pulses (single-pulse mode). We apply GHz burst mode processing to fabricate laser-induced periodic surface structures (LIPSS) on the material surfaces. In our previous work for silicon (Si), we have found that GHz burst mode can create unique two-dimensional (2D) LIPSS composed of both parallel and perpendicular to the laser polarization direction. We proposed that the formation of 2D-LIPSS is attributed to the synergetic contributions of electromagnetic and hydrodynamic mechanisms. To further investigate more detailed formation mechanisms and explore practical applications, we employ titanium (Ti), whose properties are significantly different from Si. We demonstrate that GHz burst mode fs laser pulses (central wavelength: 1,030 nm, intra-pulse width: 230 fs, intra-pulse repetition rate (an intra-pulse interval): 4.88 GHz (205 ps) and burst pulse repetition rate: 10 kHz) can also fabricate 2D-LIPSS on Ti surfaces. We attribute the dominant formation mechanism of 2D-LIPSS to the generation of hot spots with highly enhanced electric fields due to transient change of material properties during GHz burst pulse irradiation. Based on this speculation, properly tailoring the shapes of the burst pulse with an optimum intra-pulse number enables the creation of well-defined 2D-LIPSS. Furthermore, essentially homogeneous 2D-LIPSS can be formed in a large area by laser scanning of a focused fs laser beam with a stage scanning speed of 5 mm/s.

国立大学法人東京農工大学 大学院工学研究院の宮地 悟代 准教授は、同大学大学院生の立田実花氏（当時）、飯田悠斗氏（当時）とともに、半導体電子デバイスとして利用されるシリコン表面にフェムト秒レーザーを照射することにより、表面を金属化させた後に、もう一つのフェムト秒レーザーパルスを照射することによって表面プラズモンを効率良く励起することに初めて成功しました。これにより効率良くナノ領域をアブレーションできるため、新しいナノ加工技術への基礎物理過程として期待されています。

掲載論文情報

掲載誌：Scientific Reports

出版日：2023年10月27日付（電子版）

論文名：Enhancement of plasmonic coupling on Si metallized with intense femtosecond laser pulses

著者名：Mika Tateda , Yuto Iida* & Godai Miyaji*

DOI　：https://doi.org/10.1038/s41598-023-45968-6

Using a pump–probe technique, the reflectivity of a silicon grating surface irradiated with intense femtosecond (fs) laser pulses was measured as a function of the incidence angle and the delay time between pulses. After irradiating the surface with an intense s-polarized, 400 nm, 300 fs laser pulse, the reflectivity measured with a weak p-polarized, 800 nm, 100 fs laser pulse exhibited an abrupt decrease for an incidence angle of ~ 24°. The depth of the dip was greatest for a delay time of 0.6–10 ps, for which the reflectivity around the dip was highest. The surface was also found to be ablated most strongly for the conditions causing the deepest dip for a delay time of 5–10 ps. Surface plasmon polaritons (SPPs) on silicon metallized by the intense pulse are resonantly excited by the subsequent pulse, and the strong coherent coupling between the subsequent pulse and SPPs excited on the molten Si surface produced by high-density free electrons induces strong surface ablation due to the intense plasmonic near-field. The results clearly show that fs pulses can be used to significantly modulate the nature of nonmetallic materials and could possibly serve as a basic tool for the excitation of SPPs on nonmetallic materials using ultrafast laser–matter interactions.

国立大学法人東京農工大学 大学院工学研究院の宮地 悟代 准教授は、同大学大学院生の石原 陽大 氏（当時）とともに、波長650-1100nmの7fsレーザーをステンレス鋼およびチタン表面に集光照射したときに表面に形成されるナノ構造の周期が、これまでに観測されていた周期の1/5~1/4であることを初めて示しました。また、この形成メカニズムが短距離伝搬型の表面プラズモンであることを提案し、このモデルが実験結果の傾向とよく一致することを示しました。超短パルスレーザーをもちいたナノ加工技術に新しい展開を与えるものと期待しています。

掲載論文情報

掲載誌：Frontiers in Nanotechnology

出版日：2023年9月19日付（電子版）

論文名：Fine periodic nanostructure formation on stainless steel and gallium arsenide with few-cycle 7-fs laser pulses

著者名：Akihiro Ishihara and Godai Miyaji*

DOI　：https://10.3389/fnano.2023.1249648

We report the fine periodic nanostructure formation process on metal and semiconductor surfaces in air with few-cycle 7-fs laser pulses and its physical mechanism. Using appropriate peak power densities and scanning speeds for the laser pulses, nanostructures could be formed on stainless steel and gallium arsenide (GaAs) with periods of 60–110 nm and 130–165 nm, respectively, which are 1/5–1/4 of the period of nanostructures formed with 100-fs laser pulses. The periodicity can be explained as arising from the excitation of shortrange propagating surface plasmon polaritons, and the observed periods are in good agreement with the model calculation results.