• Title/Summary/Keyword: Flat-top beam

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A study of fabrication of LIPSS using flat-top beam with various materials (다양한 재질에서의 flat-top 빔을 이용한 LIPSS 형성에 관한 연구)

  • Choi, Jun-Ha;Choi, Won-Suk;Shin, Young-Gwan;Cho, Sung-Hak;Choi, Doo-Sun
    • Design & Manufacturing
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    • v.15 no.3
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    • pp.26-31
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    • 2021
  • In this study, laser-induced periodic surface structure (LIPSS) was fabricated on Ni, Si, and GaAs samples using a flat-top beam with a uniform energy distribution that was fabricated using a Gaussian femtosecond laser with a mechanical slit and tube lens. Unlike the Gaussian beam, the flat-top beam has a uniform beam profile, therefore the center and the periphery of the fabricated LIPSS have similar line periodicity. In addition, LIPSS was obtained not only in metals but also in metalloids and metals and metalloid compounds by using the narrow pulse width characteristic of a femtosecond laser.

Wide-fan-angle Flat-top Linear Laser Beam Generated by Long-pitch Diffraction Gratings

  • Lee, Mu Hyeon;Ryu, Taesu;Kim, Young-Hoon;Yang, Jin-Kyu
    • Current Optics and Photonics
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    • v.5 no.5
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    • pp.500-505
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    • 2021
  • We demonstrated a wide-fan-angle flat-top irradiance pattern with a very narrow linewidth by using an aspheric lens and a long-pitch reflective diffraction grating. First, we numerically designed a diffraction-based linear beam homogenizer. The structure of the Al diffraction grating with an isosceles triangular shape was optimized with 0.1-mm pitch, 35.5° slope angle, and 0.02-mm radius of the rounding top. According to the numerical results, the linear uniformity of the irradiance was more sensitive to the working distance than to the shape of the Al grating. The designed Al grating reflector was fabricated by using a conventional mold injection and an Al coating process. A uniform linear irradiance of 405-nm laser diode with a 100-mm flat-top length and 0.176-mm linewidth was experimentally demonstrated at 140-mm working distance. We believe that our proposed linear beam homogenizer can be used in various potential applications at a precise inspection system such as three-dimensional morphology scanner with line lasers.

Control of Intensity Distribution Profile of Laser Beam using Beam Shaping Mask with Random Array Slits (빔셰이퍼 마스크를 이용한 레이저 빔의 강도 분포 제어)

  • Oh, Jae-Yong;Park, Deog-Su;Shin, Bo-Sung
    • Laser Solutions
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    • v.15 no.2
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    • pp.11-14
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    • 2012
  • In this paper, we have made a proposal concerning the beam shaping mask(BSM) using random-array slits to control intensity distribution profile of laser beam and demonstrated its proprieties experimentally. When a lot of slits are set out irregularly, diffraction patterns of light does not appear but granularity patterns as a bundle of fibers appear. Intensity distribution profile is controlled by densities distribution of circular slits arrayed randomly because the number of slits and its area means amount of light energy through BSM. Namely as the number of slits in high intensity area is increased and that in low intensity area decreased, amount of light energy is same over all local parts. So gaussian intensity distribution could be changed to flat-top.

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Research on BTU and Short-axis Geometry of Line-beam Optics for LLO Applications (레이저 박리용 선형 빔 광학계의 빔 변환 모듈과 단축 형상에 대한 연구)

  • Lee, Seungmin;Lee, Gwangjin;Kim, Daeyong;Lee, Sanghyun;Jung, Jinho
    • Korean Journal of Optics and Photonics
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    • v.32 no.6
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    • pp.276-285
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    • 2021
  • This paper reports the study of the line-beam optical system of the laser lift-off (LLO) equipment used in the OLED manufacturing process. To obtain both a long process depth and a narrow width of the line beam, even with the poor M2 value of the laser source, the research is focused on the optical system, including the beam transformation unit (BTU). We also propose optical configurations for the super-Gaussian distribution and the fiber-based BTU for the flat-top distribution.

Reduced ion mass effects and parametric study of electron flat-top distribution formation

  • Hong, Jinhy;Lee, Ensang;Parks, George K.;Min, Kyoungwook
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.118.2-118.2
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    • 2012
  • In particle-in-cell (PIC) simulation studies related to ion-ion two-stream instability, a reduced ion-to-electron mass ratio is often employed to save computation time. But it was not clearly verified how electrons dynamics are coupled with the slower evolution of ion-ion interactions under the external electric field. We have studied the ion beam driven instability using a 1D electrostatic PIC code by comparing different rescaling of parameter with real ion mass from the reference simulation with reduced ion mass. As the external electric field is stronger, the excited unstable mode range was more sensitively affected by the system size with the real mass ratio than the reduced ion mass. The results show that the reduced mass ratio should be used cautiously in PIC code as the electron dynamics can modify the ion instabilities. Additionally we found the formation of electron flat-top distribution in the final saturation stage. Simulation results show that in the early phase electrostatic solitary waves are quasi-periodically formed, but later they are fully dissipated resulting in heated, flat-top distributions. New electron beam components are occasionally formed. These are a consequence of the interaction with solitary wave structures. We parametrically investigate the development of electron phase space distributions for various drift speeds of ion beams and temperature ratios between ions and electrons

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Lyot-Type High-Order Fiber Comb Filter Based on Polarization-Diversity Loop Structure (편광 상이 루프 구조 기반 Lyot형 고차 광섬유 빗살 필터)

  • Jo, Song-Hyun;Kim, Young-Ho;Lee, Yong-Wook
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.12
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    • pp.10-15
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    • 2013
  • In this paper, we propose a Lyot-type optical fiber comb filter based on a polarization-diversity loop structure (PDLS), which has flat-top pass bands and multiwavelength switching capability. Generally, the PDLS can remove the dependency of the filter on input polarization. The proposed filter is composed of a polarization beam splitter, two half-wave plates (HWPs), and two polarization-maintaining fiber loops concatenated with a $60^{\circ}$ offset between their principal axes. By controlling two HWPs, it can operate in a flat-top band mode or a lossy flat-top band mode with an inherent insertion loss of ~3.49dB. In particular, flat-top bands can be interleaved in both modes, which cannot be realized in a Lyot-Sagnac comb filter based on a fiber coupler. Compared with Solc-type high-order comb filters with the same order, the proposed filter shows sharper transition between pass and stop bands.

Direct UV laser projection ablation to engrave 6㎛-wide patterns in a buildup film (빌드업 필름의 선폭 6㎛급 패턴 가공을 위한 직접식 UV 레이저 프로젝션 애블레이션)

  • Sohn, Hyonkee;Park, Jong-Sig;Jeong, Jeong-Su;Shin, Dong-Sig;Choi, Jiyeon
    • Laser Solutions
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    • v.17 no.3
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    • pp.19-23
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    • 2014
  • To directly engrave circuit-line patterns as wide as $6{\mu}m$ in a buildup film to be used as an IC substrate, we applied a projection ablation technique in which an 8 inch dielectric ($ZrO_2/SiO_2$) mask, a DPSS 355nm laser instead of an excimer laser, a ${\pi}$-shaper and a galvo scanner are used. With the ${\pi}$-shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam. The galvo scanner before the $f-{\theta}$ lens moves the flat-top beam ($115{\mu}m{\times}105{\mu}m$) across the 8 inch dielectric mask whose patterned area is $120mm{\times}120mm$. Based on the results of the previous research by the authors, the projection ratio was set at 3:1. Experiments showed that the average width and depth of the engraved patterns are $5.41{\mu}m$ and $7.30{\mu}m$, respectively.

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Development Process for High Power Diode Laser for Metal Surface Hardening (금속 표면경화용 고출력 다이오드 레이저 개발 프로세스)

  • Jang, Dong-Hwan
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.21 no.2
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    • pp.11-22
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    • 2022
  • This paper presents the development process for a high-power diode laser for metal surface hardening. To combine the emissions from several laser bars, it is necessary to collimate the emitted light using an optical lens. Thus, to achieve a suitable power density and uniform beam profile, several optical layouts were proposed. To estimate the laser beam for a flat-top distribution, a numerical analysis was performed using the ZEMAX software, and the results were compared with the experimental results. With a focal lens assembled in a serial diode stack source, the design can utilize the advantage of compacting the overall beam size. Experimental results for a robotic system demonstrated the processing ability of this diode laser module in industrial laser hardening.

DPSS UV laser projection ablation of 10μm-wide patterns in a buildup film using a dielectric mask (Dielectric 마스크 적용 UV 레이저 프로젝션 가공을 이용한 빌드업 필름 내 선폭 10μm급 패턴 가공 연구)

  • Sohn, Hyonkee;Park, Jong-Sig;Jeong, Su-Jeong;Shin, Dong-Sig;Choi, Jiyeon
    • Laser Solutions
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    • v.16 no.3
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    • pp.27-31
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    • 2013
  • To engrave high-density circuit-line patterns in IC substrates, we applied a projection ablation technique in which a dielectric ($ZrO_2/SiO_2$) mask, a DPSS UV laser instead of an excimer laser, a refractive beam shaping optics and a galvo scanner are used. The line/space dimension of line patterns of the dielectric mask is $10{\mu}m/10{\mu}m$. Using a ${\pi}$ -shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam; and a telecentric f-${\theta}$ lens focuses it to a $115{\mu}m{\times}105{\mu}m$ flat-top beam on the mask. The galvo scanner before the f-${\theta}$ lens moves the beam across the scan area of $40mm{\times}40mm$. An 1:1 projection lens was used. Experiments showed that the widths of the engraved patterns in a buildup film ranges from $8.1{\mu}m$ to $10.2{\mu}m$ and the depths from $8.8{\mu}m$ to $11.7{\mu}m$. Results indicates that it is required to increase the projection ratio to enhance profiles of the engraved patterns.

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KICKER MAGNET MODULATOR IN PLS (포항방사광가속기 킼커 대출력 펄스전원장치)

  • Nam, S.H.;Jeong, S.H.;Han, S.H.;Suh, J.H.;Ha, K.M.
    • Proceedings of the KIEE Conference
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    • 1997.07e
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    • pp.1779-1781
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    • 1997
  • The 2.0 GeV Pohang Light Source (PLS) is consisted of a full energy Linac and a storage ring. Four kicker magnets are installed in the storage ring tunnel to move the stored beam orbit in the storage ring closer to the injected beam from the beam transfer line. The injected beam then falls into the storage ring beam dynamic aperture. A kicker magnet modulator drives all four kicker magnets to maintain field balance and also synchronized kick of the beam. The kicker modulator can handle 2 GeV full energy beam. The kicker magnet modulator is installed in the storage ring tunnel and under stable operation. Specification of the kicker magnet modulator is ${\sim}6.0{\mu}s$ pulse-width, 200 ns flat-top width with ${\pm}0.2%$ regulation, ${\sim}24\;kA$ peak current, and 10 Hz repetition rate. Two thyratron switches (EEV CX-1536AX) are used in the system. In this article, design, and experimental results of the kicker magnet modulator are discussed.

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