• Journal of the Optical Society of Korea
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• 제17권4호
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• pp.289-295
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• 2013

Although low-level laser therapy (LLLT) has been a valuable therapeutic technology in the clinic, its efficacy may be reduced in deep tissue layers due to strong light scattering which limits the photon density. In order to enhance the photon density in deep tissue layers, this study developed an optical tissue clearing (OTC) laser probe (OTCLP) system which can utilize four different OTC methods: 1) tissue temperature control from 40 to $10^{\circ}C$; 2) laser pulse frequency from 5 to 30 Hz; 3) glycerol injection at a local region; and 4) a combination of the aforementioned three methods. The efficacy of the OTC methods was evaluated and compared by investigating laser beam profiles in ex-vivo porcine skin samples. Results demonstrated that total (peak) intensity at full width at half maximum of laser beam profile when compared to control data was increased: 1) 1.21(1.39)-fold at $10^{\circ}C$; 2) 1.22 (1.49)-fold at a laser pulse frequency of 5 Hz; 3) 1.64 (2.41)-fold with 95% glycerol injection; 4) 1.86 (3.4)-fold with the combination method. In conclusion, the OTCLP system successfully improved the laser photon density in deep tissue layers and may be utilized as a useful tool in LLLT by increasing laser photon density.

• 한국항공우주학회지
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• 제49권9호
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• pp.771-780
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• 2021

우주물체 레이저 추적(DLR : space Debris Laser Ranging) 시스템은 인공위성까지의 거리를 측정하는 인공위성 레이저 추적(SLR : Satellite Laser Ranging) 시스템의 확장형이라고 할 수 있다. 레이저를 발사하여 수신하는 광자 왕복하는 시간을 측정하여 궤도 결정하는 시스템이다. 거리 정밀도는 mm급 단위로 측정 가능하고 현존하는 시스템 중 가장 정밀한 시스템이다. 현재 한국천문연구원은 인공위성 레이저 추적 시스템을 세종 및 거창에 구축하였고, 나로호 과학위성, 다목적 실용위성 5호의 정밀궤도를 검증하기 위해 SLR 데이터를 활용하였다. 최근 몇 년간 우주쓰레기의 추락 또는 충돌로 인해 자국의 위성이 위협받고 있고, 이는 안보적인 측면에서 자국 우주자산 보호, 국민의 안전을 보호하기 위해 우주물체 레이저 추적이 지대한 관심을 받고 있다. 본 논문에서는 인공위성 레이 추적, 우주물체 레이저 추적을 고려한 다목적형 레이저 추적 시스템의 시스템 설계를 위하여 1.5m 급 주경을 적용하였다. 그리고 주요 구성품의 성능(레이저 파장, 레이저 출력) 등을 고려하여 링크버짓 분석을 통해 시스템 예비 성능 분석을 수행하였다.

• 한국군사과학기술학회지
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• 제24권6호
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• pp.629-637
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• 2021

For the stabilization of laser output power and wavelength of the high power fiber laser, the cooling plate must be properly taken into account. In this study, three analyzing methods which are heat transfer theory, CFD and experiment are used to analyze cooling plate performance by measuring pump Laser Diode(LD) temperature. Under limited operating conditions of a cooling plate, the internal flow of cooling plate is transitional flow so that the internal flow is assumed to be laminar and turbulence flow and conducted theoretical calculation. Through CFD, temperature of pump LD and characteristics of the internal flow were analyzed. By the experiment, temperature of pump LD was measured in real conditions and the performance of the cooling plate was verified. The results of this study indicate that three analyzing methods are practically useful to design the cooling plate for the high power fiber laser or similar things.

• Journal of Periodontal and Implant Science
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• 제52권1호
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• pp.77-87
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• 2022

Purpose: This pilot study assessed the immediate in vivo effect of high peak pulse power neodymium-doped yttrium aluminum garnet (Nd:YAG) laser monotherapy on selected red/orange complex periodontal pathogens in deep human periodontal pockets. Methods: Twelve adults with severe periodontitis were treated with the Laser-Assisted New Attachment Procedure (LANAP®) surgical protocol, wherein a free-running, digitally pulsed, Nd:YAG dental laser was used as the initial therapeutic step before mechanical root debridement. Using a flexible optical fiber in a handpiece, Nd:YAG laser energy, at a density of 196 J/cm² and a high peak pulse power of 1,333 W/pulse, was directed parallel to untreated tooth root surfaces in sequential coronal-apical passes to clinical periodontal probing depths, for a total applied energy dose of approximately 8-12 joules per millimeter of periodontal probing depth at each periodontal site. Subgingival biofilm specimens were collected from each patient before and immediately after Nd:YAG laser monotherapy from periodontal pockets exhibiting ≥6 mm probing depths and bleeding on probing. Selected red/orange complex periodontal pathogens (Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia/nigrescens, Fusobacterium nucleatum, Parvimonas micra, and Campylobacter species) were quantified in the subgingival samples using established anaerobic culture techniques. Results: All immediate post-treatment subgingival biofilm specimens continued to yield microbial growth after Nd:YAG laser monotherapy. The mean levels of total cultivable red/orange complex periodontal pathogens per patient significantly decreased from 12.0% pretreatment to 4.9% (a 59.2% decrease) immediately after Nd:YAG laser monotherapy, with 3 (25%) patients rendered culture-negative for all evaluated red/orange complex periodontal pathogens. Conclusions: High peak pulse power Nd:YAG laser monotherapy, used as the initial step in the LANAP® surgical protocol on mature subgingival biofilms, immediately induced significant reductions of nearly 60% in the mean total cultivable red/orange complex periodontal pathogen proportions per patient prior to mechanical root instrumentation and the rest of the LANAP® surgical protocol.

• Medical Lasers
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• 제7권1호
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• pp.6-12
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• 2018

Introduction Energy-based devices allow for a more rapid and efficient ligation of blood vessels during operations. In the present study, we evaluated the feasibility of a laser as an alternative energy source for the vessel sealing system and determined the optimal condition of laser for an effective vessel sealing through histologic examination. Materials and Methods The arteries (5 mm diameter) harvested from porcine legs were compressed between two glass-slides to eliminate its luminal space and were irradiated with 1,470-nm diode laser under various sealing conditions, including laser power (5-30 W), irradiation time (5 or 10 seconds), and focus mode (focus or defocus). Subsequently, the irradiated vessels were fixed in 4% formaldehyde and then processed to paraffin block. The paraffinized sample was sectioned and stained with hematoxylin and eosin for histological evaluation. Results The extent of tissue change was positively correlated with duration and power of laser. In defocus mode, the irradiated vessels showed sufficient tissue denaturation for sealing effect without severe tissue destruction. Moreover, among the various conditions of irradiation, laser power between 15 and 20 W, as well as exposure time of 5 seconds were appropriate for sealing the blood vessels. Conclusion Adequate power and irradiation duration of laser can render blood vessels to be sealed effectively, although the higher power of laser may be required to cut the vessels.

• Design & Manufacturing
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• 제17권2호
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• pp.55-61
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• 2023

With femtosecond (fs) laser pulse irradiation on metals, various types of nano- and micro-scale structures can be naturally induced at the surface through laser-matter interaction. Two notable structures are laser-induced periodic surface structures (LIPSSs) and cone/spike structures, which are known to significantly modify the optical and physical properties of metal surfaces. In this work, we irradiate fs laser pulses onto various types of metals, cold-rolled steel, pickled & oiled steel, Fe-18Cr-8Ni alloy, Zn-Mg-Al alloy coated steel, and pure Cu which can be useful for precise molding and imprinting processes, and adjust the morphological profiles of LIPSSs and cone/spike structures for clear structural coloration and a larger range of surface wettability control, respectively, by changing the fluence of laser and the speed of raster scan. The periods of LIPSSs on metals used in our experiments are nearly independent of laser fluence. Accordingly, the structural coloration of the surface with LIPSSs can be optimized with the morphological profile of LIPSSs, controlled only by the speed of the raster scan once the laser fluence is determined for each metal sample. However, different from LIPSSs, we demonstrate that the morphological profiles of the cone/spike structures, including their size, shape, and density, can be manipulated with both the laser fluence and the raster scan speed to increase a change in the contact angle. By injection molding and imprinting processes, it is expected that fs laser-induced surface structures on metals can be replicated to the plastic surfaces and potentially beneficial to control the optical and wetting properties of the surface of injection molded and imprinted products.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제32권5호
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• pp.396-405
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• 2010

Purpose: This study was performed to find out the effects of the Er:YAG laser (Key Laser) & Er,Cr:YSGG laser (Water Laser) on inflammatory tissues. Materials and Methods: It was performed on about 20 g, 6 weeks male ICR mouses. They were grouped into the control (negative), the inflammation induced 'control'(positive), Er,Cr:YSGG laser exposured group after inducing inflammation, Er:YAG lasere exposured group after inducing inflammation each 15 mouses. The mouses were applicated 0.5% DNFB 1 cc on ear skin twice a day for 4 days until symptom expression. After laser exposure, ear tissues were extracted and defined gene expression by RT-PCR. Then, tissue staining, lymphocytes observation, electromicroscophic laboratory were carried out. Results: Interleukin-$1{\beta}$ was expressed much less in the A-laser exposed group. Interleukin-$1{\beta}$ & Tumor Necrosis Factor-${\alpha}$ were expressed 7 times lesser in the A-laser exposed group. The number of Lymphocytes related to inflammation was decreased rapidly in the A-laser exposed group in vivo. he number of cavity recovered normal was a little bigger in the A-laser exposed group after 5 days Conclusion: The expression of IL-$1{\beta}$ & TNF-${\alpha}$, hitologic change, observation with electron microscope shows that Erbium laser exposure causes lesser inflammation with A-laser rather than B-laser.

• 대한소아치과학회지
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• 제35권1호
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• pp.11-17
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• 2008

본 연구는 Er:YAG laser에 의한 치수의 초기 조직반응과 calcitonin gene-related peptide (CGRP) 함유 신경섬유의 발현을 비교 평가하고자 시행하였다. Er:YAG laser와 conventional bur를 이용하여 상악 제1대구치의 교합면에 와동을 형성하였다. 와동형성 후 48시간 후에 조직을 처리하여 hematoxylin-eosin 염색과 CGRP 면역조직화학을 시행한 후 다음과 같은 결과를 얻었다. 1. Conventional bur를 이용하여 삭제한 경우, 상아질 바닥면은 균열이 없는 평면의 균일한 모양을 보였으며, Er:YAG laser의 경우에는 상아질의 면은 bur에 비해서 파동형의 불규칙적인 형태와 바닥면에서 상아세관의 주행방향을 따라 미세한 균열을 보였다. 2. Er:YAG laser에 의해 손상 받은 치수에서는 혈관확장과 노출된 치수의 손상부위를 따라 bur에서 손상 받은 치수보다 더 많은 염증세포의 침윤과 상아모세포층의 파괴를 보였다. 3. 노출손상 후에 치수신경 말단에서 CGRP 발현은 bur와 laser군 모두에서 손상을 받지 않은 정상 치수에 비해서 증가된 양상을 보였으며, 그 증가된 정도는 laser의 경우에서 더 강하였다. 위의 결과들을 종합하면, Er:YAG laser가 치수손상을 최소화하여 적용되면 치아우식 제거와 와동형성과 같은 여러 수복치료 시 유용하게 사용될 수 있으리라 사료된다.

• 한국임상수의학회지
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• 제26권6호
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• pp.563-567
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• 2009

Steel scalpel과 $CO_2$ laser를 이용한 돼지 자궁 절개 시 창상 치유에 미치는 영향을 평가하고자 본 실험을 실시하였다. 다섯 마리의 Landrace - Yorkshire 혼혈 종 돼지를 이용하였고, 각각의 돼지에서 좌측 및 우측의 자궁에 대칭적으로 scalpel과 $CO_2$ laser를 이용하여 절개 하였다. 각각의 기구는 절개 속도, 절개의 용이성 및 출혈 정도를 평가 하였으며 수술 후 21일에 육안적인 유착 정도와 조직학적 검사를 실시하였다. Scalpel을 이용한 절개는 레이저를 이용한 절개보다 용이하였으나 두 군간의 유의성은 없었다. 레이저를 이용한 절개 시 출혈량은 적었으나 절개속도는 scalpel을 이용한 경우가 빨랐다. $CO_2$ laser 절개에서의 수술 후 자궁 유착은 scalpel 절개에서 보다 적게 발생하였다. 조직학적 검사에서 scalpel 절개의 경우 상피 조직과 자궁내막선의 재생이 완전히 이루어 졌으나 레이저를 이용한 경우 불완전한 재생 상태를 보였다. 비록 scalpel을 이용한 절개가 $CO_2$ laser를 이용한 경우 보다 조직 손상이 적었으며 사용하기 용이하였으나 출혈이 많은 단점이 있다. 반면 $CO_2$ laser를 이용한 절개의 경우 지혈 효과는 좋으나 창상 치유를 지연 시켰다.

• Clinical and Experimental Reproductive Medicine
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• 제26권2호
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• pp.185-192
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• 1999

The present study was performed to investigate the efficacy and safety of laser assisted hatching (AH) on mouse embryos. Non-contact $1.48{\mu}m$ diode laser system used to create a precise hole on zona pellucida. 2-cell embryos were collected from the mice (ICR) that had the coitus vaginal plug confirmed at 48 hours after hCG injection. Collected 2-cell embryos were cultured in the HTF medium supplemented with 0.4% BSA. For experiments, embryos at 8-cell stage were used after 18-22 hours in culture. After assisted hatching, the embryos were further cultured in HTF medium containing 0.1% PVP (anti-hatching system) for 3 days. For evaluate efficiency of laser on mouse embryo hatching, the effect of AH methods (acidic tyrode, pronase and laser), the number of artificial holes (1, 2 and 3 hole) and the irradiation time of laser (2, 4, 6, 8 and 10 ms) were examined. Hatching rates of laser AH group (95.2%) was significantly higher than that of control group (50.8%), but there was no differences among the laser (95.2%), acidic tyrode (100%) and pronase (98.5%) groups. Hatching rates of the number of zona pellucida opening by laser, there were no differences among the 1 hole (87.5%),2 hole (92.1%) and 3 hole (85.9%) groups. Developmental and hatching rates of embryos according to laser irradiation time were similar in the treatment groups. Therefore, these results suggest that laser AH using non-contact $1.48{\mu}m$ diode laser is a simple and accurate and effective procedure for AH. Based on these results, laser AH could be use safely for human ART program.