• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.149-150
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• 2006

We describe a novel method of scanning probe nanofabrication using a AFM(atomic force microscopy) tip with assistance of Femtosecond laser pulses to enhance fabrication capability. Illumination of the AFM tip with ultra-short light pulses induces a strong electric field between the tip and the metal surface, which allows removing metal atoms from the surface by means of field evaporation. Quantum simulation reveals that the field evaporation is triggered even en air when the induced electric field reaches the level of a few volts per angstrom, which is low enough to avoid unwanted thermal damages on most metal surfaces. For experimental validation, a Ti: sapphire Femtosecond pulse laser with 10 fs pulse duration at 800 nm center wavelength was used with a tip coated with gold to fabricate nanostructures on a thin film gold surface. Experimental results demonstrate that fine structures with critical dimensions less than ${\sim}10nm$ can be successfully made with precise control of the repetition rate of Femtosecond laser pulses.

• 한국레이저가공학회지
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• 제10권4호
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• pp.18-22
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• 2007

In this paper, we suggested the femtosecond laser processing using the mask which makes Gaussian spatial beam distribution to a normalized distribution by Fresenel diffraction. Holography pattern of the size of $320{\times}320{\mu}m^2$ on the Cr thin film on glass substrate with a pixel size of $5{\times}5{\mu}m^2$ was fabricated according to the pattern generated by the iterative Fourier transform algorithm(IFTA) algorithm. We analysed the damage threshold with an assumption the power distribution as Gaussian profile as 45 $mJ/cm^2$. The regenerated image of letters through the diffractive pattern was well recognized at the screen.

• 한국레이저가공학회지
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• 제11권1호
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• pp.25-31
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• 2008

The characteristics of femtosecond laser ablation of $Al_2O_3$ for prescision microfabrication are studied experimentally. Specifically, the process time during femtosecond laser drilling of microholes with $sub-100{\mu}m$ diameter are investigated for varying laser fluence, scan speed and beam path designs like trepanning with continuously changed start points. The accumulation of sub-micrometer size particles within the hole and the deterioration of edge clarity and roundness for decreasing hole diameter are examined and through process optimization the microdrilling with good hole quality is achieved using a femtosecond laser system (repetitionrate 1 kHz, wavelength 785 nm, pulse duration 185 fs)

• 한국레이저가공학회지
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• 제8권1호
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• pp.39-44
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• 2005

We report experimental results on the periodic patterning using a Ti:sapphire femtosecond laser (800nm, 100fs, 1kHz). Periodic structures with reproducible basic patterns are produced both on the surface and inside transparent materials. Period patterning for the application to display panel is widely investigated. Also, the submicron dot and line patterns are fabricated inside fused silica glass, which is important for the formation of diffraction grating in integrated optical circuit. finally, we demonstrate the utility of the femtosecond laser application to optical memory by fabricating the three-dimensional dot patterns.

• 한국광학회:학술대회논문집
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• 한국광학회 2005년도 하계학술발표회
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• pp.214-215
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• 2005

• 한국정밀공학회지
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• 제24권12호
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• pp.50-56
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• 2007

Femtosecond laser ablation of the Invar alloy and hole drilling for a shadow mask are studied. We used a regenerative amplified Ti-sapphire laser with a 1kHz repetition rate, 184fs pulse duration and 785nm wavelength. Femtosecond laser pulse was irradiated on the Invar alloy with air blowing at the condition of various laser peak power. An ablation characteristic of the Invar alloy was appeared non-linear at $125J/cm^2$ of energy fluence. For the application to a shadow mask, the hole drilling of the Invar alloy with the cross section of a trapezoidal shape was investigated. The ablated micro-holes were characterized using an atomic force microscopy(AFM). The optimal condition of hole pattern f3r a shadow mask was $4\;{\mu}m$ z-axis feed rate, 0.2mm/s circular velocity, $26.4{\mu}J$ laser peak power. With the optimal processing condition, the fine circular hole shape without burr and thermal damage was achieved. Using the femtoseocond laser system, it demonstrates excellent tool for the Invar alloy micro-hole drilling without heat effects and poor edge.

• 한국레이저가공학회지
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• 제14권2호
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• pp.17-23
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• 2011

Active thin films are ubiquitous in the manufacture of all forms of flat panel display (FPD). One of the most widely employed thin films is indium tin oxide (ITO) and metal films used electrically conductive materials in display industries. ITO is widely used for fabrication of LCD, OLED device, and many kinds of optical applications because of transparency in visible range and its high conductivity and metal films are also widely employed as electrodes in various electric and display industries. It is important that removing specific area of layer, such as ITO or metal film on substrate, to fabricate and repair electrode in display industries. In this work, we demonstrate efficient selective ablation process to ITO and aluminum film on glass using a femtosecond laser (${\lambda}p=1025nm$) respectively. The femtosecond laser with wavelength of 1025nm, pulse duration of 400fs, and the repetition rate of 100kHz was used for selectively removing ITO and Al on glass in the air. We can successfully remove the ITO and Al films with various pulse energies using a femtosecond laser.

• 한국레이저가공학회지
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• 제16권1호
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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.

• 한국레이저가공학회지
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• 제18권1호
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• pp.7-11
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• 2015

In this paper, micro trench structure is fabricated by femtosecond laser for inserting optical reflecting wavelength filter in planar waveguide. The width and depth of the trench is controlled by femtosecond laser machining condition. Also, large scale of single channel with 500um and 1000um on silica plate is fabricated by femtosecond laser, and roughness of the channel surface is polished by $CO_2$ laser for the insertion of the filter. Then, the characteristic of the planar waveguide inserted the filter is verified.

• 한국정밀공학회지
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• 제30권4호
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• pp.409-413
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• 2013

A polypropylene film was ablated using a $CO_2$ laser, Ti-sapphire femtosecond laser, and UV nanosecond laser. For modified atmosphere packaging, polypropylene films were ablated by laser pulse with different pulse energies and measured on an optical microscope. Also, we observed the shelf life of a banana contained within packaging of a breathable zipper bag. As a result, we have demonstrated that the breathable film can efficiently extend the shelf life of respiring foods, particularly fresh fruits and vegetables. The development of breathable film laser microfabrication system will more useful for industrial applications.