• Title/Summary/Keyword: ultrashort laser pulse

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Stabilization and characterization of a 10 GHz harmonically mode-locked Er-doped fiber ring laser by suppression of relaxation oscillation (완화진동억압을 이용한 10 GHz 고조모드잠금된 고리형 어븀첨가 광섬유 레이저의 출력 안정화 및 특성 측정)

  • 장지웅;이유승;전영민;임동건
    • Korean Journal of Optics and Photonics
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    • v.13 no.1
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    • pp.58-64
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    • 2002
  • Using Mach-Zehnder type intensity modulator, we stabilized a 10 GHz harmonically mode-locked dispersion-compensated fiber ring laser using a feedback controlling system, and we measured its stability. The laser was stabilized for more than 16 hours by controlling the cavity length to suppress the relaxation oscillation frequency component which had caused the laser output instability. The ms timing jitter and ms amplitude noise were measured to be 260-524 fsec and 4~11.5%, respectively, and BER test measurement showed a value of 10$^{-13}$ .

Simulation of an X-ray Fresnel Zone Plate with Nonideal Factors

  • Chen, Jie;Fan, Quanping;Wang, Junhua;Yuan, Dengpeng;Wei, Lai;Zhang, Qiangqiang;Liao, Junsheng;Xu, Min
    • Current Optics and Photonics
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    • v.4 no.1
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    • pp.9-15
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    • 2020
  • Fresnel zone plates have been widely used in many applications, such as x-ray telescopes, microfluorescence, and microimaging. To obtain an x-ray Fresnel zone plate, many fabrication methods, such as electron-beam etching, ion-beam etching and chemical etching, have been developed. Fresnel zone plates fabricated by these methods will inevitably lead to some nonideal factors, which have an impact on the focusing characteristics of the zone plate. In this paper, the influences of these nonideal factors on the focusing characteristics of the zone plate are studied systematically, by numerical simulations based on scalar diffraction theory. The influence of the thickness of a Fresnel zone plate on the absolute focusing efficiency is calculated for a given incident x-ray's wavelength. The diffraction efficiency and size of the focal spot are calculated for different incline angles of the groove. The simulations of zone plates without struts, with regular struts, and with random struts are carried out, to study the effects of struts on the focusing characteristics of a zone plate. When a Fresnel zone plate is used to focus an ultrashort x-ray pulse, the effect of zone-plate structure on the final pulse duration is also discussed.

10 GHz Multiuser Optical CDMA Based on Spectral Phase Coding of Short Pulses

  • Ruan, Wan-Yong;Won, In-Jae;Park, Jae-Hyun;Seo, Dong-Sun
    • Journal of IKEEE
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    • v.13 no.1
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    • pp.65-70
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    • 2009
  • We propose an ultrashort pulse optical code-division multiple-access (O-CDMA) scheme based on a pseudorandom binary M-sequence spectral phase encoding and decoding of coherent mode-locked laser pulses and perform a numerical simulation to analyze its feasibility. We demonstrate the ability to properly decode any of the multiple (eight) 10 Gbit/s users by the matched code selection of the spectral phase decoder. The peak power signal to noise ratio of properly and improperly decoded $8{\times}10 Gb/s$ signals could be greater than 15 for 127 M-sequence coding.

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Characteristics of Ultrashort Pulse Fiber Laser using Polarization Maintaining Fiber (편광유지 광섬유를 이용한 초단펄스 광섬유 레이저 제작 및 특성연구)

  • 김봉규
    • Proceedings of the Optical Society of Korea Conference
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    • 2000.02a
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    • pp.232-233
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    • 2000
  • 초단펄스를 생성하는 방법에는 이득 스위칭, 광 변조기, 모드록킹 레이저 등이 있다. 이중에서 모드록킹 광섬유 레이저를 이용한 초단펄스를 발생시키는 방법은 비용이 많이 들고 부피가 큰 단점을 갖고 있지만, 매우 짧은 펄스 폭 생성, 고 출력의 펄스생성, 그리고, 파장 및 주파수를 조절을 할 수 있다는 장점을 갖고 있다. 한편, 모드록킹 방법에는 수동형과 능동형이 있다. 수동형 방법은 아주 짧은 펄스 폭을 갖는 펄스를 발생할 수 있지만, 출력이 불안정하고 펄스의 발생주기를 조절하기 어려운 반면, 능동형 방법은 상대적으로 펄스폭은 넓지만, 안정된 출력과 펄스 발생주기를 짧게 할 수 있다. 따라서, 고 반복률의 안정된 펄스를 사용하는 초정밀 광 계측기나 광통신에 사용되는 광원으로 능동형 모드록킹 광섬유 레이저가 많이 사용되어지고 있다. (중략)

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Precision Length Metrology using the Optical Comb of Femtosecond Pulse Lasers (펨토초 레이저의 주파수 모드를 이용한 정밀 길이 측정)

  • Jin Jong-Han;Kim Young-Jin;Kim Seung-Woo
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.10a
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    • pp.216-219
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    • 2005
  • In precision length measurements using optical interferometry based on homodyne or heterodyne principles, it is crucial to have frequency-stabilized monochromatic light sources. To the end, we investigate the possibility of utilizing the optical comb constituted by ultrashort femtosecond pulse lasers generated from a gain medium of titanium-doped aluminium oxide $(Ti:Al_2O_3)$. The optical comb is stabilized by locking to the caesium atomic clock, which allows all the modes of the comb to maintain an extremely high level of frequency stabilization to precision of one part in $10^{16}$. Then, high precision length measurements are realized by extracting a single or group of particularly wanted optical frequency components or by adopting a third-party light source locked to the comb. Required measurement system setup will be presented in detail along with experimental results.

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Design and operational characteristics of cw and KLM Ti : sapphire lasers with a symmetric Z-type cavity configuration (Z-형태의 대칭형 레이저 공진기 구조를 갖는 연속 발진 및 Kerr-렌즈 모드-록킹되는 티타늄 사파이어 레이저의 설계와 동작 특성)

  • Choo, Han-Tae;Ahn, Bum-Soo;Kim, Gyu-Ug;Lee, Tae-Dong;Yoon, Byoung-Won
    • Korean Journal of Optics and Photonics
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    • v.13 no.4
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    • pp.347-355
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    • 2002
  • We have constructed a high efficiency and broad tunable cw Ti:sapphire laser with a four-mirror symmetric Z-type laser cavity to increase the laser usability. From theoretical analyses and experimental data for a symmetric Z-type laser cavity containing a Kerr medium, the cavity mode size and the Kerr-lens mode-locking (KLM) strength for KLM lasers can be confirmed as function of the position in the cavity, the intracavity laser power, and the stability parameter. As a result, the slope efficiency and the maximum average output power of cw Ti:sapphire laser at 5 W pumping power of Ar-ion laser were 31.3% and 1420 ㎽ respectively. The tunablility was ranged from 730 ㎚ to 908 ㎚ with average output power above 700 ㎽. We obtained the KLM operation easily by self-aperturing effect in the Kerr medium and the slope efficiency and the maximum average output power of KLM Ti:sapphire laser was 16% and 550 ㎽ respectively. The spectral bandwidth was 33 ㎚ at the center wavelength of 807 ㎚ and the pulse width was 27 fs with a repetition rate of 82 ㎒.

Radiography with Low Energy Protons Generated from Ultraintense Laser-plasma Interactions

  • Choi, Chang-Il;Lee, Dong-Hoon;Kang, Byoung-Hwi;Kim, Yong-Kyun;Choi, Il-Woo;Sung, Jae-Hee;Kim, Chul-Min;Kim, I-Jong;Yu, Tae-Jun;Lee, Seong-Ku;Pae, Ki-Hong;Hafz, Nasr;Jeong, Tae-Moon;Ko, Do-Kyeong;Lee, Jong-Min
    • Journal of the Optical Society of Korea
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    • v.13 no.1
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    • pp.28-32
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    • 2009
  • In order to obtain high quality images of thin objects, we performed an experiment of proton radiography by using low energy protons generated from the interaction of an ultrashort ultraintense laser with solid targets. The protons were produced from a thin polyimide target irradiated by the laser pulse, and their maximum energy was estimated at up to 1.8 MeV. A CR-39 nuclear track detector was used as a proton radiography screen. The proton images were obtained by using an optical microscope and the spatial resolution was evaluated by a Modulation Transfer Function (MTF). We have achieved about $10\;{\mu}m$ spatial resolution of images. The obtained spatial resolution shows about $4{\sim}5$ times better value than the conventional X-ray radiography for inspection or non-destructive test (NDT) purpose.

Laser Acceleration of Electron Beams to the GeV-class Energies in Gas Jets

  • Hafz, Nasr A.M.;Jeong, Tae-Moon;Lee, Seong-Ku;Choi, Il-Woo;Pae, Ki-Hong;Kulagin, Victor V.;Sung, Jae-Hee;Yu, Tae-Jun;Cary, John R.;Ko, Do-Kyeong;Lee, Jong-Min
    • Journal of the Optical Society of Korea
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    • v.13 no.1
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    • pp.8-14
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    • 2009
  • In a laser-plasma wakefield accelerator, the ponderomotive force of an ultrashort high intensity laser pulse excites a longitudinal wave or plasma bubble in a way similar to the excitation of a wake wave behind a boat as it propagates on the water surface. Electric fields inside the plasma bubble can be several orders of magnitude higher than those available in conventional RF-based particle accelerator facilities which are limited by material breakdown. Therefore, if an electron bunch is properly phase-locked with the bubble's acceleration field, it can gain relativistic energies within an extremely short distance. Here, in the bubble regime we show the generation of stable and reproducible sub GeV, and GeV-class electron beams. Supported by three-dimensional particle-in-cell simulations, our experimental results show the highest acceleration gradients produced so far. Simulations suggested that the plasma bubble elongation should be minimized in order to achieve higher electron beam energies.