• Medical Lasers
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• 제8권2호
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• pp.74-79
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• 2019

Periorbital melasma is often refractory to treatment and highly associated with rebound hyperpigmentation or mottled hypopigmentation after laser treatment in Asian patients. In this report, we describe 2 patients with cluster-1 periorbital melasma and 1 patient with cluster-2 periorbital melasma who experienced remarkable clinical improvements after microwave-generated, atmospheric-pressure, non-thermal nitrogen plasma treatments. All patients exhibited limited clinical responses after combination treatments with topical bleaching agents, systemic oral tranexamic acid, and low-fluenced Q-switched neodymium (Nd):yttrium-aluminum-garnet (YAG) lasers. Low-energy nitrogen plasma treatment at 0.75 J elicited remarkable clinical improvement in the periorbital melasma lesions without post-laser therapy rebound hyperpigmentation and mottled hypopigmentation. We deemed that a single pass of nitrogen plasma treatment at 0.75 J induces mild microscopic thermal tissue coagulation and modification within the epidermis while preserving the integrity of the basement membrane in patients with periorbital melasma. Accordingly, nitrogen plasma-induced dermal tissue regeneration could play a role in the treatment of melasma lesions.

• 한국광학회지
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• 제18권4호
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• pp.270-273
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• 2007

광섬유가 연결된 레이저 다이오드로 펌핑하는 Nd:YAG 레이저의 공진기 길이를 14 mm로 구성하고 펌핑광의 세기에 따른 946 nm Nd:YAC 레이저의 출력 특성을 조사하였다. 이때 이득 매질의 온도는 열전 냉각기를 이용하여 일정하게 유지시켰다. 그 결과 이득 매질의 온도를 낮게 유지할수록 더 강한 출력을 얻을 수 있었으며, $5^{\circ}C$에서 9.95 W로 펌핑할 때 최고 870 mW의 출력을 확인하였다. 출력거울의 반사율 변화에 따른 펌핑광의 발진 문턱값을 측정하여 0.23의 공진기 손실값을 얻을 수 있었다. 또한 펌핑광의 세기가 10 W 이상일 때 이득매질의 열적인 효과로 인한 출력의 감소 현상을 확인할 수 있었다.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 14TH KACG TECHNICAL MEETING AND THE 5TH KOREA-JAPAN EMGS (ELECTRONIC MATERIALS GROWTH SYMPOSIUM)
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• pp.165-167
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• 1998

Nd:YAG crystals were grown by Horizontal Bridgman method. The effects of sliding rate (growth rate) of Molydbenum container, growth atmosphere and concentration of Neodymium ions on crystal qualities were investigated. The size of the crystals grown was up to 150-200 mm in length, 70 mm in width and 25-35 mm in thickness. Crystals grown under the optimum conditions were violet, transparent and could not be observed any macroscopic defects. Under the polarizing microscopoc observations with crossed polar, striations, {211} facets and inclusions were detected. With the grown crystals, prototypes of laser rods for 1.06$\mu$m laser application were manufactured and then characterized. As a result, we can get high quality of Nd:YAG laser rods with <111> and <110> axis, 63 mm in length and6.3 mm in diameter.

• Medical Lasers
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• 제9권2호
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• pp.142-149
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• 2020

Background and Objectives A picosecond-domain laser treatment using a microlens array (MLA) or a diffractive optical element elicits therapeutic micro-injury zones in the skin. This study examined the patterns of tissue reactions after delivering multiple pulses of 1,064-nm, MLA-type, picosecond neodymium:yttrium-aluminum-garnet laser treatment. Materials and Methods Multiple pulses of picosecond laser treatment were delivered to ex vivo human or brown micropig skin and analyzed histopathologically. A high-speed cinematographic study was performed to visualize the multiple pulses of picosecond laser energy-induced skin reactions in in vivo human skin. Results In the ex vivo human skin, a picosecond laser treatment at a fluence of 0.3 J/cm² over 100 non-stacking passes generated multiple lesions of thermally-initiated laser-induced optical breakdown (TI-LIOB) in the epidermis and dermis. In the ex vivo micropig skin, stacking pulses of 20, 40, 60, 80, and 100 at a fluence of 0.3 J/cm² generated distinct round to oval zones of tissue coagulation in the mid to lower dermis. High-speed cinematography captured various patterns of twinkling, micro-spot reactions on the skin surface over 100 stacked pulses of a picosecond laser treatment. Conclusion Multiple pulses of 1,064-nm, MLA-type, picosecond laser treatment elicit marked TI-LIOB reactions in the epidermis and areas of round to oval thermal coagulation in the mid to deep dermis.

• Medical Lasers
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• 제10권2호
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• pp.82-89
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• 2021

Background and Objectives Due to changes in diet and lifestyle, the number of obese people worldwide is steadily increasing. Obesity has an adverse effect on a healthy life, so it needs treatment and improvement. Research related to this is continuously being conducted. Materials and Methods The laser system to compact designed using 808 nm laser diode and Neodymium Yttrium orthovanadate generates a 1064 nm wavelength, the periodically polarized nonlinear crystal pumping laser beam. The pulsed 1064 nm wavelength beam passing through the AO Q-switch is used as the pumping light of the nonlinear optical crystal and is irradiated to the periodic polarized nonlinear optical crystal with a quasi-phase matching period. Nonlinear optical crystals use an oven to control the temperature to generate the desired 1980 nm and 2300 nm wavelengths. Results The 1980 nm and 2300 nm wavelengths generated by temperature control of nonlinear optical crystals are effective for lipolysis. A fiber catheter was used so that the laser could be directly irradiated to the fat cells. In particular, the new wavelength (1980 nm, 2300 nm) can increase the fat reduction effect with low energy (1.3 W). When a laser with a combination wavelength of 1980 nm and 2300 nm was used, an average lipolysis effect of 20% was obtained. Conclusion A mid-infrared lipolysis laser system with excellent absorption of fat and water has been developed. We conducted a princlinical study to confirm the efficacy and safety of the lipolysis laser system, and obtained good results for lipolysis with low energy.

• Archives of Plastic Surgery
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• 제39권2호
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• pp.143-149
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• 2012

Background : Axillary osmidrosis is characterized by an unpleasant odor, profuse sweating, and in some instances, staining of clothes that may socially and psychologically impair affected individuals. Various types of surgical procedures have been developed for the treatment of axillary osmidrosis. This study was undertaken to evaluate the effectiveness of subcutaneous pulsed neodymium: yttrium-aluminum-garnet (Nd-YAG) laser treatment for the treatment of axillary osmidrosis. Methods : Twenty-nine patients with axillary osmidrosis were included in this study. Patients were categorized according to the results of an axillary malodor grading system, and a subcutaneous pulsed Nd-YAG laser was applied to all patients. The treatment area for the appropriate distribution of laser energy was determined using the iodine starch test (Minor's test) against a grid pattern composed of $2{\times}2cm$ squares. The endpoint of exposure was 300 to 500 J for each grid, depending on the preoperative evaluation results. The results were evaluated by measurement of axillary malodor both pre- and postoperatively using the grading system and iodine starch test. Results : The average follow-up period was 12.8 months. Nineteen patients had a fair-to-good result and ten patients had poor results. The postoperative Minor's test demonstrated that there were remarkable improvements for patients with mild to moderate symptoms. Complications including superficial second degree burns (n=3) were treated in a conservative manner. A deep second degree burn (n=1) was treated by a surgical procedure. Conclusions : Subcutaneous pulsed Nd-YAG laser has many advantages and is an effective noninvasive treatment for mild to moderate axillary osmidrosis.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.605-610
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• 2004

Solid propellants allow thrusters to be light-weight, com-pact and robust because they require neither tank nor valve, Moreover, the solid propellant will not leak, spill or slosh. Consequently, the solid propellant thruster is one of the potential candidates for the microthruster. On the other hand, the control of the solid propellant combustion is difficult, since the conventional solid propellant continues to bum until all the stored propellant is consumed. Although particular devices like thrust reverser were designed to control the combustion, these devices were rarely used in the practical rocket motors. These devices rise thruster weight as well as complicate the thruster operation. In this study, a solid propellant microthruster using laser sustained combustion was designed in order to develop a high-efficiency microthruster overcoming the previously-mentioned difficulty. This designed thruster has semiconductor lasers and non-self-combustible solid propellants in addition to the conventional solid propellant thruster. In this designed thruster, the semiconductor laser controls the combustion of the non-self-combustible solid propellant. In order to demonstrate that the solid propellant combustion is controllable with laser, some non-self-combustible solid propellants were irradiated with the laser at a back-pressure of about 1㎪. A 40-W class Neodymium Yttrium Aluminum Garnet (ND:YAG) laser was used as a tentative alternate to the semiconductor laser. This experiment has shown that the solid propellant combustion was controllable with 10- W class laser irradiation.