• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.33-36
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• 2009

Laser ablation with femtosecond lasers is highly promising for microfabrication of materials. Also, the high peak power of femtosecond lasers could induce a multiphoton absorption to ablate transparent materials. Similar results have also been were obtained in the case of optical fibers. In this paper, we present our experimental results of femtosecond laser microstructuring of optical fiber and its applications to microelectronic components and fiber optic devices. Finally, we directly produced micro holes with femtosecond laser pulses in a single step by moving an optical fiber in a preprogrammed structure. When water was introduced into a hole drilled from the bottom surface of the optical fiber, the effects of blocking and redeposition of ablated material were greatly reduced and the aspect ratio of the depth of the hole was increased. We have presented circular and rectangular-shaped holes in optical fiber.

• 동력기계공학회지
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• 제19권3호
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• pp.5-10
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• 2015

Femtosecond laser machining has been applied for creating a sensor function in silica glass optical fibers. Femtosecond laser pulses make it possible to fabricate micro structures in processed regions of a very thin glass fiber line because femtosecond laser pulses can extremely minimize thermal effects. With the laser machining to optical fiber using a single shot of 210-fs laser at a wavelength of 800 nm, it was observed that a processed region surrounded a thin layer which seemed to be a hollow cavity monitored by scanning electron microscopy (SEM). This study aims at a theoretical investigation for the processed region by using a numerical analysis in order to embed sensing function to optical fibers. Numerical methods based finite element method (FEM) has been used for an optical waveguide modeling. This report suggests two types modeling and describes a comparative study on optical losses obtained by the experiment and the numerical analysis.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.875-876
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• 2012

• Current Optics and Photonics
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• 제7권6호
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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.

• 한국정밀공학회지
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• 제30권10호
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• pp.1017-1022
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• 2013

Currently, various optical fiber tips are used to deliver laser beam for endoscopic surgery. In this paper, we demonstrated multidirectional (forward and side) firing optical fiber tip using a femtosecond micromachining and $CO_2$ laser polishing technology. We controlled the edge width of optical fiber tip, by modulating the condition of $CO_2$ laser, to regulate the amount of side and forward emission. The distal end of the optical fiber with core/clad diameter of $400/440{\mu}m$ was microstructured with cone shape by using a femtosecond laser. And then the microstructured optical fiber tip was polished by $CO_2$ laser beam result in smoothing and specular reflection at the surface of the cone structure. Finally, we operated the LightTools simulation and good agreement was generally found between the proposed model and experimental simulation.

• Current Optics and Photonics
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• 제7권6호
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• pp.708-713
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• 2023

A robust all-fiber nonlinear amplifying loop-mirror-based mode-locked femtosecond laser is demonstrated. Power-dependent nonlinear phase shift in a Sagnac loop enables stable and power-efficient mode-locking working as an artificial saturable absorber. The pump power is adjusted to achieve the lowest intensity noise for stable long-term operation. The minimum pump power for mode-locking is 180 mW, and the optimal pump power is 300 mW. The lowest integrated root-mean-square relative intensity noise of a free-running mode-locked laser is 0.009% [integration bandwidth: 1 Hz-10 MHz]. The long-term repetition-rate instability of a free-running mode-locked laser is 10^-7 over 1,000 s averaging time. The repetition-rate phase noise scaled at 10-GHz carrier is -122 dBc/Hz at 10 kHz Fourier frequency. The demonstrated method can be applied as a seed source in high-precision real-time mid-infrared molecular spectroscopy.

• Journal of the Optical Society of Korea
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• 제9권1호
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• pp.1-5
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• 2005

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.

• ETRI Journal
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• 제27권4호
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• pp.446-448
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• 2005

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.

• 한국정밀공학회지
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• 제29권3호
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• pp.339-345
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• 2012

Electrospun meshed poly-caprolactone PCL was patterned by femtosecond laser with linear grooves. As parametric variables, focus spot size, pulse energy, and scanning speed were varied to determine the affects on groove size and the characteristics of the electrospun fiber at the edges of these grooves. The femtosecond laser was seen to be an effective means for flexibly structuring the surface of ES PCL scaffolds and the width of the ablated grooves was well controlled by laser energy and focus spot size. The ablation threshold was measured to be $14.9J/cm^2$ which is a little higher than other polymers. These affects were attributed to optical multiple reflections inside nano-fibers. By the laser-induced plasma at higher pulse energies, some melting of fibers was observed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 추계학술대회 논문집
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• pp.143-144
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• 2008