• Korean Journal of Optics and Photonics
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• v.21 no.6
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• pp.254-258
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• 2010

We investigate an optical technique for beam shaping and optical amplification of a pulsed laser diode without variation of its original properties, such as repetition rate and pulse duration. The horizontal and longitudinal sizes of the pulsed laser diode are 300 and $2{\mu}m$, respectively, and its output power is $1.1mW/cm^2$. The multimodal and elliptical pulse shape of the laser diode is converted to the single-modal and Gaussian pulse shape by using a lensed optical fiber. Since the single-modal lensed fiber coupling from the multimodal pulsed laser diode degrades the output power severely, the output power of the pulsed laser diode is dramatically enhanced by using an optical amplification method based on master oscillated power amplification (MOPA). The pulse qualities of the laser diode are not changed after amplifying the pulse power and the output power was finally measured to be $29mW/cm^2$.

• Korean Journal of Optics and Photonics
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• v.32 no.2
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• pp.62-67
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• 2021

We have experimentally demonstrated sum-frequency generation (SFG) in a periodically poled lithium niobate (PPLN) crystal, using a mode-locked picosecond-pulsed fiber laser and a continuous-wave (CW) diode laser with a narrow linewidth. The mode-locked fiber laser had a center wavelength of 1560.7 nm and a spectral width of 1.1 nm, and the CW diode laser had a center wavelength of 1551.0 nm and a spectral width of 6 MHz. To effectively realize SFG, both of the spatial modes of the two lasers were made to overlap in the PPLN crystal by using a single-mode optical fiber. The pulse-mode SFG with pulsed- and CW-mode lasers was successfully observed in the spectral and time domains. These results are expected to be applicable in various ways, such as optical frequency measurement and high-resolution laser spectroscopy studies using optical frequency combs.

• Laser Solutions
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• v.12 no.4
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• pp.6-11
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• 2009

The LDS(Laser Direct Structuring) process uses thermoplastic polymers with a additive compound that serves as plating seed after the activation by laser. It can realize industry requirement such as miniaturization of electrical component, design flexibility and reduction of production steps. The purpose of this study is to introduce LDS, and to investigate the fundamental mechanism. Also the characteristics of conductive patterns were investigated with respect to laser fluence and intensity. We have used a pulsed fiber laser (wavelength : 1064nm) and copper electroless plating to fabricate conductive patterns. The result showed that laser induced metal-organic complex was caused metalization by electroless copper plating, the critical laser fluence was $1.41\;J/cm^2$ at a scan speed of 1 m/s.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.27 no.1
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• pp.51-53
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• 2016

Surgical fires require an ignition source, oxidizer, and fuel. The pulsed dye laser (PDL) has been shown to be effective in the treatment of hypertrophic scars and keloids in dermatology. With the increasing number of applications of $CO_2$, laser as ignition source has been associated with operating room fires in the otorhinolaryngologic field. There have been many case reports on PDL-induced fires in dermatology, but until now, there were no reports in the larynx. We describe a 57-year-old patient diagnosed with laryngeal hyperkeratosis treated by PDL-assisted laryngomicrosurgery. In this case, we experienced incidental PDL tip flaring during pulsed dye laser vaporization.

• Journal of Oral Medicine and Pain
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• v.24 no.4
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• pp.397-410
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• 1999

In order to obtain the basic data concerning the optimal parameters in using Nd:YAG laser as a therapeutic modality to dentinal hypersensitivity, the author prepared 3 sections of sound dentin and 10 sections of sclerotic dentin with thickness of $0.5mm{\pm}0.1mm$ from human extracted teeth of anteriors and premolars, and applied the laser energy from a fiberoptic delivered, free running, pulsed Nd:YAG laser (wavelength 1064nm, pulse duration $120{\mu}sec$, fiber diameter $320{\mu}m$) to surfaces of sound and sclerotic dentin sections for 1 second with contact/unidirectional moving mode of the fiber under speed of 3mm~4mm/sec and parameters of 0.5W/10Hz, 1.0W/10Hz, 1.5W/10Hz, 2.0W/10Hz: $62J/cm^2$, $124J/cm^2$, $187J/cm^2$, $249J/cm^2$. The author comparatively evaluated the characteristics of ultrastructural changes on surfaces of sound and sclerotic dentin sections irradiated by the pulsed Nd:YAG laser using the scanning electron microscopy. A fairly ill-defined bordered surface of partially closed and melted dentinal tubules can be seen on the scanning electron microscopic feature of the sound dentin surface irradiated by the pulsed Nd:YAG laser with energy density of $62J/cm^2$. The physical modification of sound dentin surface extensively occurred depended on the increase of energy density from $62J/cm^2$ to $124J/cm^2$, $187J/cm^2$, $249J/cm^2$. While, a fairly well-defined bordered surface of partially closed and melted dentinal tubules with thickened peritubular dentin can be seen on the scanning electron microscopic feature of the sclerotic dentin surface irradiated by the pulsed Nd:YAG laser with energy density of $62J/cm^2$. The physical modification of sclerotic dentin surface of a fairly rough, shallow depression with many cracks, thickened peritubular dentin and structureless dentinal tubules extensively occurred depended on the increase of energy density from $62J/cm^2$ to $124J/cm^2$, $187J/cm^2$, $249J/cm^2$ compared to those of sound dentin surface irradiated by the pulsed Nd:YAG laser under the same parameters. Therefore, it is recommended that the pulsed Nd:YAG laser as a therapeutic modality to dentinal hypersensitivity should be applied with the less energy density than $62J/cm^2$ on the sound dentin surface, and its energy density on the partially sclerotic dentin surface should be lower than that on the sound dentin surface to preserve tooth from unnecessary excessive structural destruction.

• Journal of Oral Medicine and Pain
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• v.22 no.2
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• pp.309-325
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• 1997

In order to set the lasing variables and evaluate, clinically, the therapeutic effects of a pulsed Nd:YAG laser on oral lesion, the author applied the laser energy from a fiberoptic delivered, free running, pulsed Nd:YAG laser (wavelength 1064nm, Pulse duration 120$\mu$sec, fiber diameter 200$\mu$m/320$\mu$m) to 22 cases of oral soft tissue lesions and 6 cases of oral hard tissue lesions. The obtained results were as follows : 1. The effective excision with contact mode and the effective hemostasis of accompanied bleeding with noncontact mode were occurred by lasing on oral soft tissue lesions with fiber diameter of 320$\mu$m under the variables of 2.0~4.0W and 20~50Hz which were controlled into high power/low pulses for excision, low power/high pulses for hemostasis, low power in granulation tissue and high power in fibrous tissue according to therapeutic goals and tissue conditions. 2. About 50% of decreasing effect on hypersensitivity was occurred by lasing with non-contact and contact mode on cervical abrasion which caused dentinal hypersensitivity with fiber diameter of 320$\mu$m under the variables of 0.7 - 1.0W and 10Hz which were applied 2~3 times with 1 week interval. 3. The effective sterilization of infected root canal and lesion of periapical abscess was occurred by lasing with contact and spiral modes on wall of root canal and periapical abscess with fiber diameter of 200$\mu$m of which the tip was placed about 1mm shorter than root canal length under the variables of 1.OW and 10Hz.

• Rapid Communication in Photoscience
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• v.4 no.3
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• pp.50-53
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• 2015

$SnO_2$ thin films were deposited on fused silica substrate by pulsed laser deposition under transverse magnetic field. We have explored the effects of magnetic field and ablation laser wavelength on the optical properties of laser-induced plasma plume and structural characteristics of the deposited $SnO_2$ films. Optical emission from the plume was monitored using an optical fiber to examine the influence of magnetic field on the population of the excited neutral and ionic species and their decay with times after laser ablation. Also, we employed photoluminescence, x-ray diffraction, and UV-Vis absorption to characterize $SnO_2$ films.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.643-651
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• 2013

This study applied a laser cleaning method (dry cleaning) that is used for cleaning semiconductor elements to dental implant cleaning. The lasers used in this study were pulsed fiber lasers with wavelengths of 1,064 and 532 nm. The peak output, energy per pulse, energy density per pulse, time of pulse experiment, and number of pulse experiments served as process variables for this study, and the variables were changed for each experiment. As a result, a laser with a wavelength of 532 nm showed much higher cleaning efficiency than its 1,064 nm counterpart. As the wavelength range decreased, the quantized energy increased and the reflection rate of the titanium used for the implant decreased; consequently, the energy absorption rate increased. Therefore, it is proposed that the energy density by wavelength has a greater influence on cleaning than does the output size.

• Journal of the Optical Society of Korea
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• v.19 no.2
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• pp.130-135
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• 2015

Based on the extended nonlinear Schr$\ddot{o}$dinger equation, the influences of the filter effect on pulse splitting in a passively mode-locked erbium-doped fiber laser with positive dispersion cavity are investigated theoretically. Numerical results show that, as the bandwidth of the spectral filter decreases, the nonlinear chirp appended to the pulse increases under the combined action of the filter effect of the super-Gaussian spectral filter and the self-phase modulation effect. On further decreasing the bandwidth, the wave breaking of the pulse takes place. In addition, by varying the pump power of the laser or the profile of the spectral filter, the influences of the filter effect on pulse splitting also change accordingly.

• Nuclear Engineering and Technology
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• v.33 no.2
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• pp.175-183
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• 2001

Various welding processes are now available for end cap closure of nuclear fuel element such as TG(Tungsten Inert Gas) welding, magnetic resistance welding and laser welding. Even though the resistance and TIG welding processes are widely used for manufacturing commercial fuel elements, they can not be recommended for the remote seal welding of a fuel element at a hot cell facility due to the complexity of electrode alignment, difficulity in the replacement of parts in the remote manner and a large heat input for a thin sheath. Therefore, the Nd:YAG laser system using optical fiber transmission was selected for Zircaloy-4 end cap welding inside hot cell. The laser welding apparatus was developed using a pulsed Nd:YAG laser of 500 watt average power with optical fiber transmission. The weldability of laser welding was satisfactory with respect to the microstructures and mechanical properties comparing with TIG and resistance welding. The optimum operation processes of laser welding and the optical fiber transmission system for hot cell operation in a remote manner have been developed The effects of irradiation on the properties of the laser apparatus were also being studied.