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손익부,고명진,김영섭,노영철 한국레이저가공학회 2009 한국레이저가공학회지 Vol.12 No.1
Ripple formation of femtosecond laser in stainless steel is investigated using 184 fs pulses with a center wavelength of 785 nm. The effect of the laser polarization relative to the translation direction is observed. For drilling with a certain aspect ratio, reflections at the hole walls take place, leading to a non-uniform intensity distribution deep inside the formed hole. Finally, it is shown that a circular polarization during the drilling process significantly improves the quality of the produced holes.
Direct Writing of a 1-to-4 Optical Splitter and Packaging Technology Using a Femtosecond Laser
Ik-Bu Sohn Sohn,Hyoung-Jong Lee,Hyoung-Ju Park,이만섭 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.4
A 1-to-N optical splitter was fabricated using a focused 785-nm femtosecond laser to directly write a series of 1-to-2 Y-junction splitters in fused silica. The femtosecond laser direct writing technique has the potential to generate not only channel waveguide, but also three-dimensional optical devices. In this paper, a 1-to-4 optical splitter and U-grooves, which are used for fiber alignment, are simultaneously fabricated in fused silica glass by using near-IR femtosecond laser pulses. The obtained splitter was characterized in terms of its optical properties at a wavelength of 1550 nm. The fiber-aligned optical splitter has a low insertion loss, less than 9 dB, including an intrinsic splitting loss of 6 dB and an excess loss due to passive alignment of a single-mode fiber. A 1-to-N optical splitter was fabricated using a focused 785-nm femtosecond laser to directly write a series of 1-to-2 Y-junction splitters in fused silica. The femtosecond laser direct writing technique has the potential to generate not only channel waveguide, but also three-dimensional optical devices. In this paper, a 1-to-4 optical splitter and U-grooves, which are used for fiber alignment, are simultaneously fabricated in fused silica glass by using near-IR femtosecond laser pulses. The obtained splitter was characterized in terms of its optical properties at a wavelength of 1550 nm. The fiber-aligned optical splitter has a low insertion loss, less than 9 dB, including an intrinsic splitting loss of 6 dB and an excess loss due to passive alignment of a single-mode fiber.
Femtosecond Laser Application to PLC Optical Devices and Packaging
Ik-Bu Sohn,이만섭,Sang-Man Lee 한국전자통신연구원 2005 ETRI Journal Vol.27 No.4
Using tightly focused femtosecond laser pulses, we produce an optical waveguide and devices in transparent materials. This technique has the potential to generate not only channel waveguides, but also three-dimensional optical devices. In this paper, an optical splitter and U-grooves, which are used for fiber alignment, are simultaneously fabricated in a fused silica glass using near-IR femtosecond laser pulses. The fiber- aligned optical splitter has a low insertion loss, less than 4 dB, including an intrinsic splitting loss of 3 dB and excess loss due to the passive alignment of a single-mode fiber. Finally, we present an output field pattern, demonstrating that the splitting ratio of the optical splitter becomes approximately 1:1.
Sohn, Ik-Bu,Kim, Youngseop,Noh, Young-Chul,Won Lee, In,Kim, Jun Ki,Lee, Ho The Optical Society 2010 Optics express Vol.18 No.19
<P>Most optical fibers are designed for forward firing i.e. the light is emitted at the distal end along the optical axis of the fiber. In some applications such as the laser surgery and laser scanners, side firing of the optical fiber is required. In this paper, we present the microstructuring of an optical fiber tip using the femtosecond laser and an arc discharging process for the multidirectional firing of the beam. The distal end of the optical fiber with diameter of 125 관m was machined into a conical structure using a femtosecond laser. The surface of the machined tip was exposed to the arc discharge using a fiber splicer. The arc discharge leads to the melting and re-solidification of the fiber tip. This results in a smoothing of laser-induced conical microstructure at the tip of the fiber. We were able to demonstrate the multidirectional (circumferential) emission of the light from the developed fiber tip.</P>
Ik-Bu Sohn,Dongyoon Yoo,Young-Chul Noh,Jae-Hee Sung,Seong-Ku Lee,최훈국,Md. Shamim Ahsan 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.3
We report on fabricating high-fill-factor plano-convex spherical and square micro-lens arrays on fused silica glass surface by using a CO2 laser-assisted reshaping technique. Initially, periodic micro-pillars are encoded on glass surfaces by means of a femtosecond laser beam, afterwards, the micro-pillars are polished several times by irradiating a CO2 laser beam on top of the micro-pillars. Consequently, a spherical micro-lens array with micro-lens size of 50 μm × 50 μm and a square micro-lens array with micro-lens size of 100 μm × 100 μm are formed on the surface of the fused silica glass. We also study the intensity distribution of light passing through the glass sample engraved with a spherical micro-lens array. The simulation result shows that the focal length of the spherical micro-lens array is 35 μm. Furthermore, we investigate the optical properties of glass samples with engraved micro-lens arrays. The proposed CO2-laser-based reshaping technique is simple and fast and shows promises for fabricating arrays of smooth micro-lenses in various transparent materials.
Femtosecond laser application to optical memory and microfluidics
Ik-Bu Sohn,Man-Seop Lee,Jeong-Sik Woo,Sang-Man Lee,Jeong-Yong Chung 한국광학회 2005 Current Optics and Photonics Vol.9 No.3
We present a novel method for three-dimensional optical memory and microchannel embedded in fused silica glass. Three-dimensional dot patterning with a femtosecond laser pulse and observation with optical microscope are performed. Dot patterns are created by use of a 0.42 N.A. objective to focus 100 fs laser pulses inside the material. We demonstrate data storage with 2 μm dot pitch and 7 μm layer spacing (36 Gbit/cm3). A three-dimensional microchannel acting as microfluidic and microoptical components is directly fabricated inside a silica glass. The optical micrographs of the microchannel are obtained by a digital camera of a microscope.
Ablation of Polypropylene for Breathable Packaging Films
Sohn, Ik-Bu,Noh, Young-Chul,Choi, Sung-Chul,Ko, Do-Kyeong,Lee, Jong-Min,Choi, Young-Jin Korean Society of Laser Processing 2006 한국레이저가공학회지 Vol.9 No.3
A Polypropylene (PP) film was ablated using a femtosecond laser with a center wavelength of 785 nm, a pulse width of 184 fs and a repetition rate of 1 kHz. Increments of both pulse energy and the shot number of pulses lead to co-occurrence of photochemical and thermal effect, demonstrated by the spatial expansion of rim on the surface of PP. The shapes of the laser-ablated PP films were imaged by a scanning electron microscope (SEM) and measured a 3D optical measurement system (NanoFocus). And, the oxygen transmission rate (ORT) of periodically laser-ablated PP film were characterized by oxygen permeability tester for modified atmosphere packaging (MAP) of fresh fruit and vegetable. Our results demonstrate that femtosecond pulsed laser is efficient tools for breathable packaging films in modifying the flow of air and gas into and out of a fresh produce container, where the micropatterns are specifically tailored in size, location and number which are easily controlled by laser pulse energy and pulse patterning system.
Nano-structuring of Transparent Materials by Femtosecond Laser Pulses
Sohn, Ik-Bu,Lee, Man-Seop,Chung, Jung-Yong,Cho, Sung-Hak Optical Society of Korea 2005 Current Optics and Photonics Vol.9 No.1
Using tightly focused femtosecond laser pulses, we produce an optical waveguide and optical devices in transparent materials. This technique has the potential to generate not only channel waveguides, but also three-dimensional optical devices. In this paper, an optical splitter and U-grooves, which are used for fiber alignment, are simultaneously fabricated in a fused silica glass using near-IR femtosecond laser pulses. The fiber aligned optical splitter has a low insertion loss, less than 4㏈, including an intrinsic splitting loss of 3㏈ and excess loss due to the passive alignment of a single-mode fiber. Finally, we demonstrate the utility of the femtosecond laser writing technique by fabricating gratings at the surface and inside the silica glass.
Ablation of Polypropylene for Breathable Packaging Films
Ik-Bu Sohn,Young-Chul Noh,Sung-Chul Choi,Do-Kyeong Ko,Jongmin Lee,Young-Jin Choi 한국레이저가공학회 2006 한국레이저가공학회지 Vol.9 No.3
A Polypropylene (PP) film was ablated using a femtosecond laser with a center wavelength of 785 ㎚, a pulse width of 184 fs and a repetition rate of 1 ㎑. Increments of both pulse energy and the shot number of pulses lead to co-occurrence of photochemical and thermal effect, demonstrated by the spatial expansion of rim on the surface of PP. The shapes of the laser-ablated PP films were imaged by a scanning electron microscope (SEM) and measured a 3D optical measurement system (NanoFocus). And, the oxygen transmission rate (ORT) of periodically laser-ablated PP film were characterized by oxygen permeability tester for modified atmosphere packaging (MAP) of fresh fruit and vegetable. Our results demonstrate that femtosecond pulsed laser is efficient tools for breathable packaging films in modifying the flow of air and gas into and out of a fresh produce container, where the micropatterns are specifically tailored in size, location and number which are easily controlled by laser pulse energy and pulse patterning system.