• Journal of Korean Physical Therapy Science
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• v.7 no.2
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• pp.533-543
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• 2000

This study was designed to evaluate the analgesic effect of low power GaAsAl laser on the pain threshold of mechanical stimulation using different treatment points, acupuncture point (zusanli) and non-acupuncture points(back). Furthermore, we investigated the analgesic effect of low power GaAsAl laser using the different duration and intensity of laser in mechanical stimulation induced pain behavior. The results were summarized as follows: 1. The threshold of mechanical stimulation was significantly increased by GaAsAl laser stimulation into zusanli point after 15 and 30 min after laser stimulation(P<05). However, the laser stimulation into non-acupoint did not affect the pain threshold of mechanical stimulation. with dose dependent manner. 2. In order to investigate the analgesic effects of BV depending upon different intensities of laser stimulation, the experimental animals were divided into three groups: 3 mW treated group, 6 mW treated group and 10 mW treated group. The low power GaAsAl laser stimulation was applied into zusanli acupoint for 30 min with different intensity of laser stimulation. Six and ten mW of laser stimulation significantly increased the pain threshold of mechanical stimulation at 15 min after laser stimulation as compared to that of control group(P<.05). Moreover, the analgesic effect of 10 mW laser stimulation was maintained for 30 min after laser stimulation (P<.05). 3. Finally, we tested the analgesic effect of 10 mW laser stimulation using different duration such as 10 min, 30 min or 1 hr after application of mechanical stimulation. In 30 min treatment group, the pain threshold of mechanical stimulation was increased at 15min and 30min after laser stimulation(P<.05). However, laser stimulation for 60 min dramatically increased the pain threshold of mechanical stimulation at 0 min after laser stimulation and the analgesic effect of laser stimulation was observed until 1 hr after laser stimulation. In conclusion, these data apparently demonstrate that low power GaAsAl laser has analgesic effect on mechanical induced pain model in rats. In addition, the treated point, intensity and duration of laser stimulation should be concerned before clinical application for pain management purpose.

• Laser Solutions
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• v.11 no.4
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• pp.13-20
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• 2008

The damage threshold measurement of gold films is carried out with ultrashort-pulse laser. An enhanced two temperature model is developed to encounter the limitation of linear modeling during ultrashort pulse laser ablation. In which the electron heat capacity is calculated using a quantum mechanical approach based on a Fermi-Dirac distribution, temperature-dependent electron thermal conductivity valid beyond the Fermi temperature is adopted, and reflectivity and absorption coefficient are estimated by applying a temperature-dependent electron relaxation time. The predicted damage threshold using the proposed enhanced modelclosely agreed with experimental results, demonstrating the importance of considering transient thermal and optical properties in the modeling of ultrashort pulse laser ablation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.3
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• pp.591-596
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• 1994

Threshold dependence on stripe width in gain-guided single quantum well lasers has been examined by complex domain effective index method. It is found, in narrow stripe regime, that the lateral optical confinement estimated by newly introduced parameters decreases very rapidly as the transverse optical confinement factor decreases. Thus, in a single quantum well laser with a usually very small, the optical confinement may become very poor depending on stripe width not only in the transverse but also in the lateral direction, further enhancing the gain saturation and often leading to an anomalously high threshold current. The understanding of rather anomalous threshold dependence on stripe width will be very important in optimization of quantum well laser diode structure.

• Journal of Oral Medicine and Pain
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• v.23 no.1
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• pp.1-9
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• 1998

The aim of the study was to evaluate the anesthetic Effecs of pulsed Nd:YAG laser irradiation to the oral mucosa and the teeth. Twenty subjects who didn't have a history of significant systemic or current oral disease were included in this study. All the subjects were divided randomly into the experimental group and the control group with 10 for each group. Pain thresholds were measured with Weighted Needle Pinprick Sensory Threshold Test for the mucosal surface of lower lip and with electric pulp test for the upper right central incisor respectively, before and immediately after pulsed Nd:YAG laser irradiation in the condition of 2 watt, 20pps for 2 minute at 10mm distance. The experiment was double-blinded clinical trial. The results were as follows : 1. The mean pain threshold of the mucosal surface of lower lip for Weighted Needle Pinprick Sensory Threshold Test was 2.94(1.00g for the contral group respectively, and there was no statistical difference between two groups. 2. The mean pain threshold of the mucosal surface of lower lip was significantly increased immediately after pulsed Nd:YAG laser irradiation. 3. The mean pain threshold of the upper right central incisor for eledtric pulp test was 34.50(4.97V in the experimental group and 34.00(13.08V in the control group respectively, and there was no statistical difference between two groups. 4. The mean pain threshold of the upper right central incisor was significantly increased immediately after pulsed Nd:YAG laser irradiation.

• Physical Therapy Korea
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• v.5 no.2
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• pp.1-14
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• 1998

This study was conducted to examine the increasing effects of Ga-As-Al laser Koryo-hand acupuncture on experimental pressure threshold. Forty healthy subjects (female=20. male=20) aged 21 to 30 years were randomly assigned to two treatment groups with same ratio in sex. The subjects in the experimental group (n=20) received Ga-As-Al laser stimulation, and those in the control group (n=20) received sham stimulation on appropriate Koryo-hand acupuncture points M10 on the left hand which is reflex point of upper trapezius portion. Experimental pressure threshold at the contralateral upper trapezius was determined with a pressure algometer and Galvanic Skin Response (GSR) before and after treatment. The change of pressure threshold between pretreatment and posttreatment in the experimental group was greater than that in the control group (p<0.05). The result indicates that Ga-As-Al laser Koryo-hand acupuncture increases experimental pressure threshold and suggests that it is an effective noninvasive pain management technique.

• Physical Therapy Korea
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• v.4 no.1
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• pp.87-94
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• 1997

The purposes of this study were 1) to determine the changes between pre-treatment and post-treatment of four groups of 15 persons each and 2) to compare the effect of conventional transcutaneous electrical nerve stimulation(TENS) and laser at auricular acupuncture points on experimental pain threshold measured at the wrist. Sixty healthy adult men and women(M:32, F:28), aged 20 to 28 years, were assigned randomly to one of four groups. Group 1 received TENS to the appropriate auricular point for wrist pain, Group 2 received laser to the appropriate auricular point for wrist pain, Group 3 received placebo TENS to the appropriate auricular point for wrist pain, Group 4 received no treatment and served as controls. Experimental pain threshold at the wrist was determined with a painful electrical stimulus before and 20 minutes after ear stimulation. Group 1 was the only group that showed a stastically significant increase (p<0.05) in pain threshold after treatment whereas the Group 2,3 and 4 did not. These results suggest that TENS has the capability to higher pain threshold but laser does not.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.29-33
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• 2010

We have investigated fs-laser ablation as well as optoperforation threshold of PDMS (Polydimethylsiloxane) thin lid cover on ${\mu}$-channel with changing the flow medium from water to hemoglobin. The ablation threshold is found to be independent of both PDMS thin film thickness and flow medium, but the optoperforation threshold is dependent on the films thickness. The observation that the ablation process is well described with simple two-temperature model supposed that the cover lid PDMS of $\mu$-channel be processed with minimized thermal effects by fs-laser with low laser fluence.

• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.387-394
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• 1997

The influences of laser-induced damage threshold by the after-processing of $Al_2O_3$ thin films was investigated. The samples were fabricated at the substrate temperature of $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$ and $350^{\circ}C$ respectively, and the LIDT were measured by using Nd:YAG laser. After the processing with baking and laser conditioning of the samples, the variation of LIDT was measured. It was found that LIDT was enhanced twice by laser-conditioning process and 1.5 times by baking process. In addition, we measured the chemical properties of the thin film structure before and after the processing by using XPS.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.288-289
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• 2005

To study the photon statistics, the total counts probability was measured for the two different optical source : below-threshold with Bose-Einstein distribution, and above-threshold laser with Poisson distribution.

• Journal of the Optical Society of Korea
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• v.6 no.3
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• pp.59-71
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• 2002

Photonic band gap structures have a high potential for nearly zero-threshold lasers. This paper describes new-types of low-threshold photonic crystal lasers fabricated in InGaAsP slab waveguides free-standing in air. Two-types of photonic crystal lasers are studied. One is a single-cell nano-cavity laser formed in a square array of air holes. This photonic band gap laser operates in the smallest possible whispering gallery mode with a theoretical Q >30000 and exhibits low threshold pump power of 0.8 mW at room temperature. The nther laser does not have any cavity structure and the lasing operation originates from the enhanced optical density of states near photonic band edges. A very low threshold of 35 $\mu$W (incident pump power) is achieved from this laser at 80 K, one of the lowest values ever reported. This low threshold is benefited from low optical losses as well as enhanced material gain at low temperature.