• Title/Summary/Keyword: Ultra-short pulse laser

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Theoretical Analysis on the Optimum Fluence for Copper Ablation with a 515 nm Picosecond Laser (515 nm 피코초 레이저를 이용한 구리 어블레이션 공정의 최적 에너지밀도에 대한 이론적 분석)

  • Shin, Dongsig;Cho, Yongkwon;Sohn, Hyonkee
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.10
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    • pp.1009-1015
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    • 2013
  • Ultra-short laser pulses are effective, when high requirements concerning accuracy, surface roughness and heat affected zone are demanded for surface structuring. In particular, picosecond laser systems that are suited to be operated in industrial environments are of great interest for many practical applications. This paper focused on inducing optimum process parameters for higher volume ablation rate by analyzing a relationship between crater diameter and optical spot size. In detail, the dependency of the volume ablation rate, penetration depth and threshold fluence on the pulse duration 8 ps and wavelength of 515 nm was discussed. The experimental results showed that wavelength of 515 nm resulted in less threshold fluence ($0.075J/cm^2$) on copper than IR wavelength ($0.3J/cm^2$). As a result, it was possible that optimum fluence for higher volume ablation rate was achieved with $0.28J/cm^2$.

A Study on the Improvement of Resolution of Optical Coherence Tomography System Using Femto-Second Laser (펨토초 레이저를 이용한 OCT 시스템의 분해능 향상에 관한 연구)

  • Yang, Sung-Kuk;Park, Yang-Ha;Chang, Won-Suk;Oh, Sang-Ki;Kim, Hyun-Duk
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.18 no.6
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    • pp.31-36
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    • 2004
  • Optical coherence tomography system has been extensively studied because it has some advantages such as imaging of high resolution, low cost, and compact size configuration. In order to obtain high resolution of OCT system we configured OCT system using a femto-second laser. We measure the pulse width using autocorrelator function because a femto-second laser is ultra short pulse. And we measured the practical resolution using theoretical equation and the measurement of reference sample. It is confirmed that the proposed OCT system has 1.5 times higher resolution and un distinctive cross-sectional image than OCT system with SLD as a light source.

Ultrafast Femtosecond Lasers: Fundamentals and Applications (펨토초 레이저의 원리 및 응용)

  • Kim, Young-Jin;Kim, Yun-Seok;Kim, Seung-Man;Kim, Seung-Woo
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.6
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    • pp.7-16
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    • 2010
  • Physical fundamentals of ultrashort femtosecond lasers are addressed along with emerging applications for precision manufacturing and metrology. Femtosecond lasers emit short pulses whose temporal width is in the range of less than a picosecond to a few femtoseconds, thereby enabling extremely high peak-power machining with less thermal damages. Besides, the broad spectral bandwidth of femtosecond lasers constructed in the form of frequency comb permits absolute distance measurements leading to ultraprecision positioning control and dimensional metrology.

Study of The Anisotropy of Electron Energy Distribution of Optical-Field Ionized Oxygen Plasma by Using Polarization Spectroscopy

  • Kim, Dong-Eon;Kim, Jae-Hoon;Kawachi, Tetsuya;Hasegawa, Noboru;Sukegawa, Kouta;Iwamae, Atsushi;Fujimoto, Takashi
    • Journal of the Optical Society of Korea
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    • v.7 no.3
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    • pp.145-149
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    • 2003
  • The anisotropy of electron energy distribution in oxygen plasmas produced by a high intensity laser was investigated by using polarization spectroscopy. An ultra-short pulsed laser with a pulse duration of 66.5 fs and a power density of $1 {\times} 10^17/ W/$\textrm{cm}^2$$ was used. At this power density and pulse duration, the plasma was generated predominantly by optical field ionization. The degree of polarization of OVI 1s$^2$2p$^2$p2- 1s$^2$4d$^2$D$^{0}$ (J = 1/2-3/2 and 3/2-5/2) transition line at 129.92 $\AA$ was measured. O VI 1s$^2$2p$^2$P$^2$ -1s$^2$4s$^2$S$^2$ (J = 1/2-1/2 and 3/2-1/2) transition line at 132.26 $\AA$ was used to calibrate the sensitivity of the optical system. The dependencies of the degree of polarization on the initial gas density and on the laser polarization were investigated. When the laser polarization was changed from a linear to a circular polarization, the degree of polarization was decreased. When the initial gas density was increased, the degree of polarization was decreased.

Optical pulse parameter analysis of gain switched InGaAIP FP LD at 650 nm wavelegth and its characteristic in comparison with CW operation (이득스위칭을 이용한 650nm InGaAIP FP LD의 광펄스 파라메터 분석 및 CW 발진과의 특성비교)

  • 오광환;채정혜;이용탁;백운출;김덕영
    • Korean Journal of Optics and Photonics
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    • v.12 no.2
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    • pp.135-142
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    • 2001
  • Recently, plastic optical fiber draws a lot of attention as a new transmission medium for local area network (LAN) and home network applications. As PMMA based GI-POF (Graded Index Plastic Optical Fiber) has very low loss at about 500 nm and 650 nm wavelengths, it is very important to have a compact ultra short optical pulse source at these wavelength windows. In this paper, we have investigated detailed characteristics of gain switched laser system by using a commercially available low cost RF devices and an InGaAlP Fabry Perot semiconductor laser operating at 650 nm wavelength. The shortest optical 'pulse obtained was 33 psec with 1 GHz repetition rate. Depending on the DC bias current and the modulation frequency, the FWHM and the pulse energy of the gain switched pulses show 33.3-82.8 psec and 0.97-9.69 pI respectively. Also, the spectral bandwidths for CW and gain switched operations are 0.44 nm and 1.50 nm. We believe that these results are quite useful for high bit rate optical transmission applications with PMMA based plastic optical fibers in addition to estimate properties of ultra fast optical components and electro-optic devices. vices.

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3D Printing-Based Ultrafast Mixing and Injecting Systems for Time-Resolved Serial Femtosecond Crystallography (시간 분해 직렬 펨토초 결정학을 위한 3차원 프린팅 기반의 초고속 믹싱 및 인젝팅 시스템)

  • Ji, Inseo;Kang, Jeon-Woong;Kim, Taeyung;Kang, Min Seo;Kwon, Sun Beom;Hong, Jiwoo
    • Korean Chemical Engineering Research
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    • v.60 no.2
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    • pp.300-307
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    • 2022
  • Time-resolved serial femtosecond crystallography (TR-SFX) is a powerful technique for determining temporal variations in the structural properties of biomacromolecules on ultra-short time scales without causing structure damage by employing femtosecond X-ray laser pulses generated by an X-ray free electron laser (XFEL). The mixing rate of reactants and biomolecule samples, as well as the hit rate between crystal samples and x-ray pulses, are critical factors determining TR-SFX performance, such as accurate image acquisition and efficient sample consumption. We here develop two distinct sample delivery systems that enable ultra-fast mixing and on-demand droplet injecting via pneumatic application with a square pulse signal. The first strategy relies on inertial mixing, which is caused by the high-speed collision and subsequent coalescence of droplets ejected through a double nozzle, while the second relies on on-demand pneumatic jetting embedded with a 3D-printed micromixer. First, the colliding behaviors of the droplets ejected through the double nozzle, as well as the inertial mixing within the coalesced droplets, are investigated experimentally and numerically. The mixing performance of the pneumatic jetting system with an integrated micromixer is then evaluated by using similar approaches. The sample delivery system devised in this work is very valuable for three-dimensional biomolecular structure analysis, which is critical for elucidating the mechanisms by which certain proteins cause disease, as well as searching for antibody drugs and new drug candidates.