• Laser Solutions
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• v.4 no.2
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• pp.1-12
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• 2001

This study has been performed to evaluate basic characteristics of CW-CO$_2$ laser welding process of A5083 and A7N01 Al alloy. The effect of welding parameters, such as shielding gas, gas flow rate, laser power and welding speed on the bead shape and porosity from bead on plate welding tests have been investigated. Welds shielded by He gas had deeper penetration and better bead shape than those shielded by Ar. The penetration depth was augmented with the increase of laser Power and the decrease of welding speed. Welds of A7N01 alloy had deeper penetration than those of A5083 alloy In beads of A5083 alloy which has deeper penetration, the volume fraction of porosities was high due to the number of its was few, but size of its was larger. The case of deeper penetration beads of A7N01 alloy, the porosity reduced under relatively higher power The Volume fraction of porosities in weld of A5083 alloy was significantly higher than that in weld of A7N01 alloy.

• Korean Journal of Bronchoesophagology
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• v.4 no.2
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• pp.219-224
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• 1998

Bilateral vocal cord paralysis can result in severe airway compromise. Over the years a variety of arytenoidectomy procedures have bee described, and one or more of these have been the gold standard for many years. A widely accepted treatment is endoscopic laser total arytenoidectomy. However, vocal results are usually poor. Objective : To evaluate the effect of treatment of endoscopic laser medial partial arytenoidectorny for bilateral vocal cord paralysis Material and Methods : We performed endoscopic medial partial arytenoidceomy with $CO_2$laser for 3 patients with bilateral vocal cord paralysis. The $CO_2$laser is operated with a continuous 7-watt beam in superpulse mode. We compared degree of dyspnea and glottic area of pre-operation with those of post-operation for 3 patients. We analysed aerodynamic study pre-operatively and post-operatively for 1 patient. Results The symptom of dyspnea was improved markedly and the glottic area was widened from 34% to 50% compared with that of pre-operation. The voice quality was slightly decreased. Tracheotomy was not necessary for not-tracheotomized patient and decanulation was possible for tracheotomized patient post-operatively. Cunclusion： The endoscopic laser medial partial arytenoidectomy is a convient and effective method for opening the posterior glottic airway.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.482-485
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• 1997

A new laser Doppler velocimeter employing a $CO_2$laser has been developed by using its optogalvanic effect. A change in the electric impedance of a discharge, induced by mixing of a returned wave with an originally existing wave inside the cavity, was employed to detect the Doppler frequency shift. A Doppler frequency shift as much as 60 KHz was detected, and also a good linear relationship between the velocity and the Doppler frequency shift was obtained.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.21 no.3
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• pp.298-302
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• 1999

Currently dental laser is used at a variety of dental treatment and many favorable clinical case reports are presented. We performed this study for the presentation of the validity of dental laser which are available and supportable in the oral and maxillofacial surgery. From October, 1998 to March, 1999, dental laser was used in 70 cases. Male patients were 38, female 32. The age ranged from 5 to 77, with a mean of 45.4. Indicated cases were 18 chronic periodontitis, 11 infections, 6 atypical pain, malignant or benign tumor, precancerous lesion, abnormal frenum, TMJ disorder, mucocele, and so forth. $CO_2$ laser(Sharplan 15F, Sharplan Co.) was used in 40 cases, Ho-YAG laser(Duopulse 2000, Excel Co.) 11, Nd-YAG(Duopulse 2000, Excel Co.) 18. We present and discuss about the objectiveness, availability, and future application of laser with case reports.

• Laser Solutions
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• v.2 no.3
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• pp.11-18
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• 1999

This paper describes the weldability of carbon steel and stainless steel using 5㎾ $CO_2$ laser system with nearly multi-mode beam and a parabolic focusing mirror. In the laser welding of steels, major welding parameters are focal point, travel speed, beam power, shield gas and gap tolerance, etc.. Two kinds of gases(Ar, He) were used as a assist gas and supplied through the external nozzle. It is very important for optimum condition to remove plasma plume which absorbs laser beam and to obtain deep penetration and sound weld bead. Bead-on-plate welding tests were carried out for the experiments. Penetration data were obtained with various welding parameters and the effects of welding parameters were discussed. Butt welding tests were performed with various conditions. Only the optimum laser parameters assured good weld quality As a result of this study, We achieve the fundamental weldabilities using a high power $CO_2$ laser for carbon steel and stainless steel.

• Journal of Welding and Joining
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• v.20 no.1
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• pp.34-40
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• 2002

The laser strengthening of $35kgf/\textrm{mm}^2$ grade steel sheet is investigated by using $CO_2$ laser beam irradiation. The increase of tensile strength is dominated by the number of fully penetrated melting lines. Also, the optimal laser irradiation pattern is obtained by 3-point bending test. Local laser strengthening clay be effective for the weight reduction of automobile components where the tailored welded blank can not be applied.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.228-234
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• 2002

The CO$_2$ laser beam irradiation strengthening of 35kgf/mm$_2$ grade steel sheet is investigated to reduce the weight of bumper beam. The increase of tensile strength is dominated by the number of fully penetrated melting lines. The optimal laser irradiation pattern is obtained by 3-point bending test of hat-type specimens. Laser should be irradiated not only on the center specimen densely in the width direction, but also on the edge densely in the longitudinal direction. Local laser strengthening may be effective for the weight reduction of automobile bumper beam.

• Korean Journal of Optics and Photonics
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• v.32 no.3
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• pp.120-125
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• 2021

We have developed a linearly polarized high-power Yb-doped fiber laser in the master oscillator power amplifier (MOPA) scheme for efficient spectral beam combining. We modulated the phase of the seed laser by pseudo-random binary sequence (PRBS), with the bit length optimized to suppress stimulated Brillouin scattering (SBS), and subsequently amplified seed power in a 3-stage amplifier system. We have constructed by coiling the polarization-maintaining (PM) Yb-doped fiber, with core and cladding diameters of 20 ㎛ and 400 ㎛ respectively, to a diameter of 9-12 cm for suppression of the mode instability (MI). Finally, we obtained an output power of 1.004 kW with a slope efficiency of 83.7% in the main amplification stage. The beam quality factor M² and the polarization extinction ratio (PER) were measured to be 1.12 and 21.5 dB respectively. Furthermore, the peak-intensity difference between the Rayleigh signal and SBS signal was observed to be 2.36 dB in the backward spectra, indicating that SBS is successfully suppressed. In addition, it can be expected that the MI does not occur because not only there is no decrease in slope efficiency, but also the beam quality for each amplified output is maintained.

• Proceedings of the Korean Society of Laser Processing Conference
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• 1999.11a
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• pp.5-6
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• 1999

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.3
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• pp.295-305
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• 2018

We present a passively Q-switched monolithic Er:Yb:glass microchip laser developed in our lab. The microchip laser can produce pulses at 1535 nm of the 'eye-safe' wavelengths with the pulse energy of 50 uJ and the pulse width of 4-6 ns. Using the laser we also designed and developed a pulsed Er:Yb:glass microchip laser rangefinder. Expressions for background and signal power, noise, and signal-to-noise ratio are reviewed. A computer simulation was used to optimize laser power, receiver aperture, and preamplifier bandwidth for the efficient system design of the laser rangefinder. Experimental results are presented to compare with the theory.