• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.1-1
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• 2000

This paper presents a holography through high scatter mediums. Femtosecond light pulses are used as object light and reference light. When light passes through a high scatter medium, there are ballistic light, snake light and difussive light in transmitting light. However, ballistic and snake light are very weak, difussive light is very stronge so that they can not be imaged directly, By using femtosecond laser electronic holographic gating method to gate ballistic light and snake light and multi-holograms processing technology, high quality images can be obtained. (omitted)

• Laser Solutions
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• v.16 no.1
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• pp.5-9
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• 2013

We have successfully formed filament inside of a transparent soda-lime glass using a Ti:sapphire based femtosecond laser. To make filament form, keeping the laser intensity higher than critical intensity is essential. Also each of the machining parameters plays an important role for the formation of filament. In this paper, we study what parameter can possibly influence for formation of filament, and we introduce an application using filamentation by femtosecond laser for transparent material.

• Current Optics and Photonics
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• v.7 no.1
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• pp.90-96
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• 2023

We numerically solve the nonlinear Schrödinger equation for pulse propagation in a passively mode-locked Yb:KGW laser. The soliton-like pulse formation as a result of balanced negative group-delay dispersion (GDD) and nonlinear self-phase modulation is analyzed. The cavity design and optical parameters of a previously reported high-power Yb:KGW laser were adopted to compare the simulation results with experimental results. The pulse duration and energy obtained by varying the small-signal gain or GDD reproduce the overall tendency observed in the experiments, demonstrating the reliability and accuracy of the model simulation and the optical parameters.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.203-206
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• 2006

Femtosecond laser-induced nano-patterning of an Al surface coated on a slide glass is reported in this paper. It was found that the period of the laser-induced nano-patterning was much dependent on the incident laser power and pulse number. Through finely adjusting the laser power and pulse number, uniform nano-patterns could be formed on the Al surface. It is based on the interference of the incident laser beam with some form of a surface scatted electromagnetic wave. It was also found that an Al oxide layer played an important role in forming the nano-patterning on the Al surface.

• Korean Journal of Materials Research
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• v.15 no.12
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• pp.796-801
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• 2005

In order to reduce the weight of glass in architecture, automobile, bottles, displays, a new technique that can strengthen glass was developed using various method. Generally, the strength achieved of glass-ceramics is higher as is 1.he fracture toughness by the formation of a crystalline phase inside glass. In this study, $70SiO_2-20Na_2O-10CaO-10TiO_2$ glasses were irradiated to strengthen by heterogeneous phase using femto-second laser pulse. Laser pulse irradiation of samples was analyzed by DTA, TMA, XRD, nano-indenter and SEM. Samples irradiated by laser had lower value$(3\~4\times10^{-3}Pa)$ of nano indentation which related with mother glass$(8\times10-3Pa)$ than values. Microcracks were occurred around laser irradiation area when femtosecond laser with the repetition rate of 1kHz was used as the light source to induced heterogeneous phase.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.184-189
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• 2005

An experimental study of the femtosecond laser machining of Si materials was carried out. Direct laser machining of the materials for the feature size of a few micron scale has the advantage of low cost and simple process comparing to the semiconductor process, E-beam lithography, ECM and other machining process. Further, the femtosecond laser is the better tool to machine the micro parts due to its characteristics of minimizing the heat affected zone(HAZ). As a result of line cutting of Si, the optimal condition had the region of the effective energy of 2mJ/mm-2.5mJ/mm with the power of 0.5mW-1.5mW. The polarization effects of the incident beam existed in the machining qualities, therefore the sample motion should be perpendicular to the projection of the electric vector. We also observed the periodic ripple patterns which come out in condition of the pulse overlap with the threshold energy. Finally, we could machined the groove with the linewidth of below $2{\mu}m$ for the application of MEMS device repairing, scribing and arbitrary patterning.

• Korean Journal of Optics and Photonics
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• v.29 no.1
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• pp.1-6
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• 2018

In this study, ray-tracing software was used to calculate the optical path length of an optical system. Using the optical path length, the optical phase, group delay (GD), group delay dispersion (GDD), and third-order dispersion (TOD) of the optical system were obtained. Pulse compressors using a prism pair or grating pair were designed to compensate the GDD of a real optical system for a femtosecond fiber laser. Also, a pulse stretcher using a grating pair with lenses or mirrors was designed. The results of this study can be used to calculate the dispersion of an optical system and optimize the performance of an ultrashort pulse laser optical system.

• 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).

• Laser Solutions
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• v.11 no.4
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• pp.13-20
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• 2008

The damage threshold measurement of gold films is carried out with ultrashort-pulse laser. An enhanced two temperature model is developed to encounter the limitation of linear modeling during ultrashort pulse laser ablation. In which the electron heat capacity is calculated using a quantum mechanical approach based on a Fermi-Dirac distribution, temperature-dependent electron thermal conductivity valid beyond the Fermi temperature is adopted, and reflectivity and absorption coefficient are estimated by applying a temperature-dependent electron relaxation time. The predicted damage threshold using the proposed enhanced modelclosely agreed with experimental results, demonstrating the importance of considering transient thermal and optical properties in the modeling of ultrashort pulse laser ablation.

• 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.