• Journal of Institute of Control, Robotics and Systems
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• v.11 no.6
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• pp.496-501
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• 2005

This paper presents experimental results of the frequency offset locking of He-Ne lasers and the stability analysis. The master laser is free running, and the slave laser is a single-mode operating laser. The frequency difference of two lasers is stabilized to 200 MHz which can be synchronized using PLL servo. The measured beat frequency between two lasers was 200.004 MHz ${\pm}$ 0.15 MHz. The square root of Allan variance as a measure of stability in time domain is also measured. The long-term stability of the beat was worse than sort-term stability. With a gate time $\tau=1000\;s$, the square root of Allan variance was about 1 GHz. The results of the square root of Allan variance of the stabilized beat signal was a gate time of $\tau=1000\;s$, the square root of Allan variance was about 1.5 kHz. The long-term stability was improved by more than several hundred times compared with that without the stabilization.

• Laser Solutions
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• v.16 no.1
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• pp.1-4
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• 2013

The optical properties of III-V compound semiconductor structure was investgated by photoreflectance (PR). The results show two signals at 1.42 and 1.73eV. These are attributed to the bandgap energy of GaAs, AlGaAs, respectively. Also, AlGaAs region showed weak signal. This signal is attributed to carbon or si defect.

• The Korean Journal of Pain
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• v.14 no.1
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• pp.51-55
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• 2001

Background: Oral mucositis is a common complication of anticancer chemotherapy. The sequelae of this consist of an increased risk of infection, moderate to severe pain, compromised oral function, and bleeding. This study was performed to evaluated the effects of the He-Ne laser and the Ga-Al-As laser on oral mucositis caused by anticancer chemotherapy in pediatric patients. Methods: There were 3 cases of osteosarcoma and 6 cases of leukemia. All patients received He-Ne laser (632.8 nm wavelength, power 60 mW) application on 400-600 Hz scanning for 5-20 minutes and Ga-Al-As laser (904 nm wavelength, power 40 mW) application by fiberoptic hand piece placed in immediate proximity to the tissue without direct contact with it for 30 seconds per point for 5 days per week. During the application patients wore wavelength-specific dark glasses and were instructed to keep their eyes closed. Results: The mean number of treatments with oral intake was $4.89{\pm}0.64$. The mean number of total treatments was $9.44{\pm}2.59$. There were no significant side effects during and after the laser treatments. Conclusions: He-Ne laser and Ga-Al-As (IR) laser treatment were well tolerated and reduced the severity and duration of chemotherapy-induced oral mucositis in pediatric oncologic patients.

• Journal of Korean Physical Therapy Science
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• v.9 no.1
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• pp.17-24
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• 2002

This studies were to investigate the effects of low power wavelengths Helium-Neon Infra-Red(He-Ne IR)laser on the changes of the blood biochemical components in burn rats. The thirty Spraque-Dewely adult male rats were assigned to the 5 groups; the experimental groups(3), the burn control group(1) and the control group(1). There was made three degree burn by the 250mW IR on the back of each rats, from 3 days after being, burned, the experimental laser groups were irradiated low power wavelengths (292Hz, 1168Hz, 4672Hz) He-Ne IR laser for 5 minutes every day during the 7days. The results wee as follows: The activities of aspirate aminotransferase(AST), alanine aminotransferase(ALT), and lactate dehydrogenase(LDH), on treated with the wavelengths ((292Hz, 1168Hz, 4672Hz) laser groups during 5 min. for 7 days were significantly increased to the control group respectively, but those of total cholesterol(CHOL) and alkaline phosphatase(ALP) were significantly decreased to the a control group (p<0.05). there were significantly decreased on the activity of alanine aminotransferase and alkaline phosphatase on the all experimental groups to the burn control group and those of lactate dehydronase on treated with 292Hz and 4672Hz wavelength9 groups to the burn control group but, were significantly increased on those of urea nitrogen (292Hz and 1168Hz)(p<0.05). The activity of AST, LDH, on treated with 1168Hz wavelengths were significantly decreased of the 292Hz and 4672Hz wavelengths groups that of ALT on the treated with 1168Hz group was significantly increased to the 4672 Hz wavelength group but those of CHOL and LDH on the 1168Hz and 4672Hz wavelength groups were dignificatly decreased to the MHz wavelengths group. As above results, the changes of the activities of biochemical conponents in the serum levels on the healing process have meaningful effected of the role of low power wavelengths He-Ne IR laser.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.4
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• pp.160-167
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• 2007

In this paper, we presented the development results of high speed wavefront sensor which is used in diagnosing the beam quality of He-Ne laser for adaptive optics system. The beam quality information of laser in AO system is necessarily required for diagnosing the optical components or correcting the distorted wavefront afterward. According to system requirements, normally, it is requested that there are high precision of measurement and real time processing speed. The developed wavefront sensor in this paper achieved maximum 30Hz of measurement rate and ${\lambda}/20(\;{@}\;{\lambda}=0.6328{\mu}m)$ of measurement precision in RMS. We also applied the developed into an experimental adaptive system and verified the performance of it by correcting the aberrated wavefront with a rate of 30Hz and $\lambda$/20 precision using the combination of the developed and PID control algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.1
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• pp.96-101
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• 2004

In order to measure the retina thickness, there are to need the 3-D retina photographing and the high speed signal processing system. In this paper, we introduced the retina photographing system and the 16-channel high speed image data acquisition system. There are able to measure the retina thickness with sensing image the returned laser signal to APD sensor after there were projected the HeNe laser on retina. We developed the laser projection system to sense a reflected image of the retina using APD sensor, the 16-channel high speed A/D converter and PCI master interface card for image transmission into computer.

• Journal of Haehwa Medicine
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• v.9 no.1
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• pp.387-397
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• 2000

Background : Intravascular Laser Irrardiation of Blood(ILIB) is used in disorder of cerebral and peripheral blood circulation, dysfunction of brain, atherosclerosis etc., but there are little study about ILIB in oriental medicine. We wished to assess the efficacy of ILIB for the treatment of cerebral infarction. Method : The study group comprised 40 patients who arrived at hospital during 48 hours after attack. All patient were divided into two group. The control group was treated with Uhuangcheongsimhuan(牛黃淸心丸), Seonghyangjeonggisan(星香正氣散), acupuncture therapy only, while the ILIB group was treated with above therapy plus 5 days of irradiation of He-Ne Laser(1.8~2.5mW, 50min. per day). In rat model of middle cerebral artery(MCA) occlusion, the control group was not treated, while the ILIB group was treated with irradiation of He-Ne Laser(1.8~2.5mW, 24sec.). Result : 1. Symptom improve scores did not showed significant difference between control and ILIB group. 2. Vasoreactivity of carotid siphon did not showed significant difference between control and ILIB group. 3. Vasoreactivity of radial artery did not showed significant difference between control and ILIB group. 4. PT a-PTT did not showed significant changes between before and after treatment in both group. Fibrinogen significantly increased after treatment in ILIB group(p<0.05)), but it was in normal degree. 5. ILIB showed a significant decrease of brain ischemic area and edema in rat model of middle cerebral artery(MCA) occlusion. Conclusion : These findings suggest that additional treatment of ILIB is not more useful than traditional therapy only in acute cerebral infarction. But ILIB showed potential effect in rat model of MCA occlusion. So further investigation will be necessary.

• Korean Journal of Optics and Photonics
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• v.1 no.1
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• pp.33-39
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• 1990

By developing a computer simulation code for discharge excited KrF excimer laser, we analyzed mainly the effects of buffer gas for the $KrF^*$ formation. the $KrF^*$ relaxation. and the absorption of the laser radiation. The $KrF^*$ formation efficiency were found to be 7.5%, 19% and the $KrF^*$ relaxation kinetic reactions were found to be 45%, 30% at the charging voltage of 30 KV and He. Ne buffer gas. respectively. But the absorption of the 248 nm laser radiation were less than 10% by the buffer gas.er gas.

• Biomedical Science Letters
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• v.13 no.3
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• pp.223-230
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• 2007

Low power laser and neuromuscular electrical stimulation have been utilized in many clinical applications for the treatment of musculoskeletal lesion. This study was to investigate the effects of low power He-Ne IR laser and neuromuscular electrical stimulation on the change of the serum biochemical components in experimentally induced muscle injured rats. The twenty Sprague-Dawley male rats were randomly assigned to the 4 groups: the normal group (n=5), the control group (n=5), the low power laser irradiation group (LLI) (n=5) and the neuromuscular electrical stimulation group (NMES) (n=5). The experimentally induced muscle injury was induced by the subcutaneous injection of a 0.1 ml Freund's Complete Adjuvant into the right hind paw and calf muscles in control, LLI and NMES groups. The LLI group was irradiated with He-Ne IR laser for 5 minutes every day during 10 days. Also, the NMES group was electrically stimulated 15 minutes every day during 10 days. The normal and control groups were not received with any therapeutic intervention. The authors performed tests which were the concentration of the serum biochemical components to detect the effects of therapeutic interventions. The results were as follows: 1. The level of the aspartate aminotransferase (AST) was significantly decreased in the LLI and NMES groups compare to the control group. 2. The level of the serum lactate dehydrogenase (LDH) was significantly decreased in the LLI and NMES groups compare to the control group. 3. The level of the serum creatine kinase (CK) was significantly decreased in the LLI and NMES groups compare to the control group. From the results, we could come to the conclusion that low power laser and neuromuscular electrical stimulation could be accelerating healing processes of skeletal muscle injury and further clinical work will be required.

• Biomedical Science Letters
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• v.6 no.3
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• pp.223-228
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• 2000

The purpose of this study was to find out the effect of He-Ne, IR laser therapy for 4 and 10 minutes on healing of septic arthritis. Sprague-Bawley rats (212.1$\pm$10 g) were randomly assigned to one control and three arthritis groups. Septic arthritis groups were divided into arthritis control, 4 or 10 minute laser therapy groups. Arthritis was experimentally induced by intraperitoneally administration of staphylococcus aureus in citrate buffer(pH 4.3). These result were obtained as follows: AST, LDH, ALP, CK activities and IgG concentration in 10 minute laser group were signifantly increased compare with those in the arthritis group. AST, LDH and CK activities in 4 minute laser group were significantly decreased compare with those in the arthritis group. We think that laser therapy in 4 minute may effective on the healing of septic arthritis. And we will have to study of the effect of laser therapy on healing mechanism, appropriate time of septic arthritis.