• Laser Solutions
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• v.17 no.4
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• pp.7-13
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• 2014

In this work, the application of laser induced breakdown spectroscopy (LIBS) for the composition analysis of thin $Cu(In,Ga)Se_2$ (CIGS) solar cell films ($1-2{\mu}m$ thickness) is reported. For the ablation of CIGS films, femtosecond (fs) laser (wavelength = 343nm, pulse width = 500fs) and nanosecond (ns) laser (wavelength = 266nm, pulse width = 5ns) were used under atmospheric environment. The emission spectra were detected with an intensified charge coupled device (ICCD) spectrometer and multichannel CCD spectrometer for fs-LIBS and ns-LIBS, respectively. The calibration curves for fs-LIBS and ns-LIBS intensity ratios of Ga/Cu, In/Cu, and Ga/In were generated with respect to the concentration ratios measured by inductively coupled plasma optical emission spectrometry (ICP-OES).

• Korean Journal of Optics and Photonics
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• v.1 no.2
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• pp.185-190
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• 1990

Balanced CPM ring dye laser was fabricated. Pulses as short as 62 fs were measured using noncollinear second harmonic generation autocorrelator. The optimum conditions were studied by changing the concentration of staturable absorber, pumping power of Ar+ laser and alignments of the intracavity four-prism sequence.

• Korean Journal of Optics and Photonics
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• v.10 no.5
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• pp.430-438
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• 1999

We have utilized soft-aperturing by gain media to develop a high-power tunable Ti:Sapphire laser with sub-40-fs and broad tuning range. The tunable spectral range was only limited by the bandwidth of mirrors. We made use of knife-edge slits near an intra-cavity prism controlled by micro-stepping-motors to tune the center wavelength continuously. The tunability of the center wavelength was ranged from 770 nm to 870 nm, and the measured pulsewidth was sub-40 fs throughout the above spectral range. The shortest pulsewidth was about 17 fs at the center wavelength of 820 nm and the spectral bandwidth was 72 nm. At 5 W pumping power of the Ar-ion laser we obtained average output power of 440 mW~580 mW. For the cw and Kerr-lens mode-lodking conditions, we have evaluated the value of an amplitude modulation to be ${\gamma}=2.5{\times}10^{-8}/W$ from the calculated waists of a Gaussian beam on the Ti:sapphire crystal surface. Using this result we demonstrate that the generation of sub-40-fs Kerr-lens mode-locked pulse can be described by the Ginzberg-Landau model which is a weak pulse shaping model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.1-7
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• 2014

A stretchable polymeric membrane shaped diffuser was used to homogenize the coherent laser beam. The developed RGB module was used to focus and defocus test by beam combiners. Average oscillation frequency was set at 180Hz~300Hz and it resulted in the best homogenization effect in visual range. The blue laser module turned out to be the worst case for the transmission and primary reason is believed to be the short length of irradiated laser beam. The developed system removed the speckling and the brightness was decreased by 10 ~ 20% for the RGB laser. Overall the brightness was decreased by 13% and homogenity with respect to the temporal axis was improved from 30fs to 110fs.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.238-239
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• 2001

sub-30fs 펄스폭의 상용 Ti：sapphire 레이저시스템에 대한 펄스압축기 및 2차 조화파 발생기를 제작하여 특성을 평가하였다. 그림la에서 82MHz의 주파수로 모드록되는 상용 Ti：sapphire 레이저 (Spectra-Physics Millennia/Tsunami laser)의 출력이 반사경 Ml, M2를 거쳐 펄스압축기에 입사되고 압축되어 나온 펄스가 다시 M6, M7를 거쳐 2차 조화파발생기로 입사되는 2단구조로 설계되었다. 압축기에 입사되기전 평균파워는 파장 800nm에서 520mW로 측정되었으며, 측정된 스펙트럼 반치폭 47nm에 (그림 2a)에 대해 chirp-free sech$^2$t 펄스로 가정할 경우 본 레이저시스템의 변환한계 펄스폭은 14.5fs로 계산된다. (중략)

• Korean Journal of Optics and Photonics
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• v.11 no.1
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• pp.43-46
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• 2000

We generated 9-fs pulses from a Kerr-lens mode-locked Ti:sapphire laser only using commercial optical components. Two sets of prisms pair made of fused silica were used to compensate group delay dispersion inside and outside the laser oscillator respectively, and broadband mirrors were used to obtain a broad spectrum. By comparison between reflectance curves of the broadband mirrors and those of previous ones, broadband mirrors which have high reflectance bandwidth of over 180 nm were found to be essential to produce sub-IO-fs pulses. ulses.

• Proceedings of the Optical Society of Korea Conference
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• 1995.06a
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• pp.190-194
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• 1995

Additive-pulse modelocking 시법을 이용하여 레이저 다이오드에 의해 펌핑된 Nb:YLF 레이저에서 1.5 ps의 펄스폭을 갖는 펄스를 얻었으며, Kerr-lens modelocking 기법에 의해 Ti:S 레이저에서 27fs의 펄스를 얻었다. 이러한 극초단 레이저의 구성과 모드록팅 원리를 설명하며, 이들을 효울적을 증폭하여 극초단 고출력 레이저로 구성하는 Chirped pulse amplification 기법에 대해 설명한다.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.29-33
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• 2010

We have investigated fs-laser ablation as well as optoperforation threshold of PDMS (Polydimethylsiloxane) thin lid cover on ${\mu}$-channel with changing the flow medium from water to hemoglobin. The ablation threshold is found to be independent of both PDMS thin film thickness and flow medium, but the optoperforation threshold is dependent on the films thickness. The observation that the ablation process is well described with simple two-temperature model supposed that the cover lid PDMS of $\mu$-channel be processed with minimized thermal effects by fs-laser with low laser fluence.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.711-713
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• 2017

Fiber Brag grating sensors were written in standard Ge-doped telecom optical fiber (Corning SMF-28) using an 800nm femtosecond laser and a phase mask. It were exposed to gamma-radiation up to a dose of 100 kGy to evaluate the radiation effect. The fs-FBG-2 sensor showed incomplete optical characteristics during irradiation, but the fs-FBG-1 sensor showed excellent radiation resistance with Bragg wavelength shift(BWS) of less than 10pm at a dose of 100 kGy.

• Proceedings of the Optical Society of Korea Conference
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• 1999.08a
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• pp.72-73
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• 1999