• Proceedings of the KWS Conference
• /
• 2004.05a
• /
• pp.106-108
• /
• 2004

레이저용접은 대부분의 소재를 고품질로 접합하는 것이 가능하지만, 단위 용접길이당 비용이 매우 높은 고비용 용접공정이다. 따라서 레이저용접에서는 고비용의 단점을 상쇄시킬 수 있을 정도의 우수한 용접품질이 유지되어야 하므로 용접부 품질의 관리가 무엇보다도 중요하다. (중략)

• Laser Solutions
• /
• v.3 no.2
• /
• pp.13-24
• /
• 2000

The weldability of dissimilar materials between sintered materials which are consisted of Co, Co＋Ni and carbon steel has been investigated using CO$_2$ laser. Autogeneous CO$_2$ laser welding were run along the butt between two alloys using sets of parameters variation-power and travel speed. In order to study weldability, mechanical tests (bending strength test, microhardness test) and metallurgical analyses (microstructure, phase transformation, fracture mode) were carried out. From the results obtained, it was found that the porosity which exists in a weld metal greatly affects the soundness of the weld. The optimum energy input to have a proper strength over than the requirement by a specification, found to be around 0.3-0.35kJ/m. There are two kinds of fracture mode in the weld metal, depending upon alloy combination, brittle fracture in the case of Co-carbon steel and a ductile fracture in the case of Co＋Ni-carbon steel. In general, Co＋Ni sintered material showed a better weld properties as compared to the Co sintered material.

• Korean Journal of Optics and Photonics
• /
• v.15 no.4
• /
• pp.343-348
• /
• 2004

We report the design and basic operating characteristics of an radio frequency excited waveguide $CO_2$ laser. Four picecs of waveguide channels are placed in one laser cavity to increase a power per unit length with the form of a 2 ${\times}$ 2 matrix. Four independent optical outputs are measured from the front of output coupler, and these beams are combined to a Gaussian mode beam far from the output coupler. A 12 W output power has been obtained with $CO_2$ : $N_2$ : He : Xe = 1 : 1 : 3 : 0.2 of the gas mixture and 200 W of radio frequency.

• Laser Solutions
• /
• v.18 no.3
• /
• pp.14-19
• /
• 2015

A helical fabricating method using $CO_2$ laser was utilized for producing cone-shaped structure on a silica substrate. Output power and the number of scanning radiation were modified in order to control the structure. The experiment shows that the depth and width of cone-shape were increased with higher output power of the laser and the number of scanning. We demonstrate fabrication of multidirectional side-firing optical fiber with diameter of 440 um using the $CO_2$ laser fabrication technique.

• The Journal of Korean Academy of Prosthodontics
• /
• v.57 no.1
• /
• pp.1-7
• /
• 2019

Purpose: The laser processability of dental prosthesis is investigated using two ceramic composites, including 3M, Lava Ultimate and Ivoclar vivadent, IPS e.max. Materials and methods: The $CO_2$ laser, picosecond laser and femtosecond laser are used to assess the processing power of dental prosthetic materials Lava Ultimate and IPS e.max and the line processing shape was measured using a confocal microscope. Results: The brittleness, carbonization and micro crack of the ceramic composite were influenced by heat accumulation of the material and could be controlled by the laser power and pulse time. Conclusion: In the case of $CO_2$ lasers, micro crack and carbonation occurred immediately, and in the picosecond laser processing, the micro cracks are partially improved, but the carbonization occurs continuously. Finally, we confirmed the high efficiency of laser processing with femtosecond laser. In particular, Lava Ultimate, a ceramic resin composite material, showed the best processability when processed using a femtosecond laser.

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

• Journal of Oral Medicine and Pain
• /
• v.34 no.3
• /
• pp.257-260
• /
• 2009

Gingival hyperpigmentation may cause esthetic problems, especially in patients with a gummy smile. This report presents the use of the $CO_2$ laser for gingival depigmentation. Two cases presented with the same chief complaint of unesthetic gingiva caused by melanin hyperpigmentation. The $CO_2$ laser was setted at 0.8 watt, 40Hz, 0.01sec. The procedure were performed with non-contact mode in all pigmented areas. Ablation of the gingival hyperpigmentation areas were accomplished without any bleeding complications or postoperative pain. After 2 weeks and 4 weeks later, healing is completed and hyperpigmented gingiva appeared pink and firm.

• Korean Journal of Optics and Photonics
• /
• v.6 no.1
• /
• pp.21-25
• /
• 1995

Q-switched Waveguide $CO_{2}$ laser using polygon mirror were constructed and their output characteristics were measured. Waveguide was made of the beryllium oxide tube of inner diameter of 2 mm, outer diameter of 20 mm, and length of 200 mm. A flat ZnSe output coupler of 80% reflectivity was placed on the 9 mm distance from the end of the waveguide. Convex lens was used to reduce the coupling loss between the polygon mirror and the waveguide. The polygon mirror was located behind of convex lens. With this condition, continuous output of the laser were measured as 1.2 W. In the Q-switched mode. pulse width 120 ns were measured with rotational speed 7,559 RPM. and peak power of up to 250 W. 250 W.

• Korean Journal of Optics and Photonics
• /
• v.15 no.4
• /
• pp.337-342
• /
• 2004

Laser optical power stabilization of a radio frequency excited $CO_2$ slab laser using the opto-Hertzian effect generated from the laser itself is achieved on the peak of the Doppler broadened gain curve. The opto-Hertzian signal was generated by a modulation of the optical flux circulating inside the laser cavity from a variation in the cavity length caused by the vibrations of the PZT. The opto-Hertzian signal is directly coupled from a RE discharge chamber via a loop antenna into a detector and applied to a lock-in stabilizer as an reference signal. The power stability of an RF excited slab laser is estimated to be better then 0.2%.

• Korean Journal of Optics and Photonics
• /
• v.33 no.1
• /
• pp.22-27
• /
• 2022

We fabricate a polarization-independent dielectric multilayer thin-film diffraction grating for a spectral-beam-combining (SBC) system with a simple grating structure and low aspect ratio. Due to the refractive index and thickness error of the manufactured thin films, the diffraction efficiency of the fabricated diffraction grating was lower than that of the design. The causes of the errors were analyzed, and it was confirmed through simulation that diffraction efficiency could be compensated through an additional coating on the manufactured diffraction grating. As a result of sputtering an additional Ta₂O₅ layer on a fabricated diffraction grating, the diffraction efficiency was corrected and a maximum 91.7% of polarization-independent diffraction efficiency was obtained.