• Laser Solutions
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• v.11 no.4
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• pp.1-6
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• 2008

This paper describes microscale laser structuring of electrospun(ES) PCL and PET nanofiber meshes. Electrospinning produces non-woven meshes of synthetic or natural materials fibers with diameters ranging from micron down to the nanometer scales that are advantageous for the supporting the growth of the small scale structures. Ultrashort laser found to be effective on the fabrication of engineeredtissue scaffold with minimum heat affect and ultra precision ablation patterns. The affect of energy range for ablation quality was analyzed and ablation characteristics of PCL and PET were compared.

• Journal of the Optical Society of Korea
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• v.7 no.3
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• pp.160-164
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• 2003

Materials processing by ultrashort pulsed laser is actively being applied to micromachining technology due to its advantages with regard to non-thermal machining. In this study, materials processing with ultrashort pulses was studied by using the high repetition rate of a 800 nm Ti:sapphire regenerative amplifier. This revealed that the highly precise micromachining of metallic thin film and bulk glass with a minimal heat affected zone (HAZ) could be obtained by using near damage threshold energy. Grooves with diffraction limited sub-micrometer width were obtained with widths of 620 nm on Cr thin film and 800 nm on a soda-lime glass substrate. The machined patterns were investigated through SEM images. We also phenomenologically examined the influence of variations of parameters and proposed the optimal process conditions for microfabrication.

• Current Optics and Photonics
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• v.7 no.6
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• pp.732-737
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• 2023

A high-power Yb-doped femtosecond (fs) fiber laser at a repetition rate of 1.83 GHz is reported. By employing a 5-stage repetition rate multiplier, the repetition rate of the mode-locked master oscillator was multiplied from 57.1 MHz to 1.83 GHz. The ultrashort pulse output at 1.83 GHz was amplified in a two-stage Yb-doped fiber amplifier, leading to >100 W of fs laser output with a pulse duration of 290 fs. The theoretical pulse width along the fiber was simulated, showing that it was in good agreement with experimental results. Further improvement in power scaling is discussed.

• Optical Science and Technology
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• v.7 no.2
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• pp.27-33
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• 2003

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.80-85
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• 2009

An experimental study of energy absorption and x-ray emission from ultrashort laser pulse irradiation of in-situ produced solid clusters has been performed. Silver clusters produced by a 30 mJ, 300 ps laser pulse were irradiated up to an intensity of $3{\times}10^{17}\;W/cm^2$ by a 70 mJ, 45 fs compressed laser pulse from the same Ti:sapphire laser. Absorption of the laser light exceeding 70% was observed, resulting in an x-ray yield (>1 keV) of ${\sim}60{\mu}J$ pulse. This may constitute a much simpler means of intense x-ray generation using ultrashort laser pulses as compared to the irradiation of structured / pre-deposited cluster targets, and it offers higher x-ray conversion efficiency than that from gas clusters and planar solid targets.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.891-894
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• 2014

The ultrashort electron pulse, laser-emitted from the metal tip apex has been characterized and used as a probing source for a new electron microscope to visualize the morphology of the gold-mesh in the nanometric resolution. As the gap between the tungsten tip and Au-surface is approached within a few nm, the large electromagnetic field enhancement for the incident P-polarized laser pulse with respect to the tip-sample axis is strongly observed. Here, we demonstrate that the time-resolved tip-enhanced electron emission microscope (TEEM) can be implemented on the laboratory table top to give the two-dimensional image, opening lots of challenges and opportunities in the near future.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.986-993
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• 2000

In this paper, we analyze transmission characteristics of ultrashort laser pulses using the properties of high-order pulses which are systematically obtained following their orders. The high-order pulses are easily derived from a modified PRS system model. But we make clear they are very useful to cover wider area and to show more accurate transmission characteristics of ultrashort pulses than Gaussian or Sech pulse approximations used conventionally. These are based on the fact that the spectra and bandwidths of the high-order pulses are geautifully related to their orders. First modifying the generalized PRS system model, we propose a new model for deriving any type of high-order pulse. And we offer a novel analysis method of ultrashort pulse transmission varying the order of the pulse from n=1 to n=100, we obtain spectra of ultrashort pulses with 1(ps)∼150(fs) FWHM's, which are widely used in optical pulse communications. One-step further, we derive PSD's of their pulse-tr ins when they are applied to Unipolar signaling scheme. These PSD's are decided in the range of possible pulse intervals. All of these results are not only coincided with some conventional experimental works but will be applied to any pioneering ultrashort pulse in the future.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.185-186
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• 2009

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.13-22
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• 2006

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.833-837
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• 2003

The spectral and temporal characteristics of a V-groove AIGaAs-GaAs quantum wire (QWR) laser were investigated with varying the cavity length. At cavity lengths shorter than 300 ${\mu}{\textrm}{m}$, a discrete shift in tile wavelength occurred from the n=1 to the n=2 subband due to the increased cavity losses. Utilizing this characteristic, ultrafast lasing characteristics at each subband were investigated by tile gain switching method.