• Journal of Biomedical Engineering Research
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• v.17 no.4
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• pp.499-506
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• 1996

Blood flow velocimeter is an essential device to measure the blood flow in skin tissue. In this study, we developed a high-speed LDV(laser Doppler Velocimeter) that has real time processing capability using a DSP(digital signal processing) chip and is able to continuously measure information about blood-flow based on a noninvasive method using self-mixing type laser diode. This LDV system has a simpler structure than any other typical blood flow velocimeter and is composed of new self-mixing probe, stabilizer circuits DSP board, and interf'ace boule We measured velocity of speaker-unit by operational frequencies to identify Doppler effect of this system, performed clinical experiment on bare finger tip and compared it with a commercial euipment BPM403A(USA).

• Korean Journal of Optics and Photonics
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• v.3 no.1
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• pp.50-54
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• 1992

Maskless depositon of copper onto n-doped and p-doped Si in an aqueous copper sulfate solution is investigated. On p-doped Si substrates, microscopic $(~10\mu\textrm{m}$) copper spots are deposited by illuminating continuous wave $Ar^+$ laser beam of wavelength 514.5 nm. Copper deposition on n-doped Si substrates is also achieved by shinning second harmonic pulses $(pulse width~25 nsec, \lambda=530 nm)$ of a passively Q-switched Nd:YAG laser. The observed deposition is attributed to the electric field resulting from the Galvanic potential of a semiconductor-electrolyte junction.

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.115-120
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• 2003

We have developed laser micro-machining technology for fabrication of the micro thin-film inductors. After the thin layers of FM/M/FM films were coated to the silicon substrate by using the conventional sputtering method, the new laser machining was applied to the patterning process that used to be carried out by the semiconductor lithography procedure. A CW Nd:YAG laser operating in TEM$\sub$00/ mode was actively Q-switched to obtain the very short pulse of 200 ns. The laser micro-machining process with pulse energy and repetition rate have been optimized as 5 mJ/pulse and 5 kHz, respectively, to obtain the line resolution as fine as 20 $\mu\textrm{m}$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.7 s.349
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• pp.1-6
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• 2006

We show for the first time the optical properties of the selectively oxidized vertical cavity laser (VCL) - depleted optical thyristor (DOT), which has not only a low threshold current, but also a high sensitivity to the optical input light. In order to analyze their switching characteristics, nonlinear s-shaped current-voltage characteristics are calculated and the reverse full-depletion voltages (Vneg's) are obtained as function of semiconductor parameters by using a finite difference method (FDM). The selectively oxidized PnpN VCL-DOT clearly shows the nonlinear s-shaped current-voltage and lasing characteristics. A switching voltage of 5.24 V, a holding voltage of 1.50 V, a spectral response at 854.5 nm, and a very low threshold current of 0.65 mA is measured, making these devices attractive for optical processing applications.

• The Journal of Korean Physical Therapy
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• v.15 no.3
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• pp.239-250
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• 2003

This study was performed to investigate the effect of low power laser irradiation on Substance P(SP) expression in the burned skin of the rats. Burns of about 3cm in diameter were created with $75^{\cric}C$ water on the back of the rats, and the lesion of experimental group were irradiated on days 1, 2, 3 and 4 postwounding. Control leasions were not irradiated. After burns, low power laser irradiation was applied by using 1000Hz, 830nm GaAlAs(Gallium-aluminum-arsenide) semiconductor diode laser. The expression of evaluated Substance P(SP) immunohistochemistry on rabbit anti-SP The results of this study wereas follows 1. The Substance P was expressed in the lamina I and II of dorsal horn of spinal cord. In expression of SP, the lesion of control group made SP to more induce significantly than experimental leasions. 2. SP immunoreactivity in burned leasion of spinal cord were decreased markedly 4 days after burns, and decreased gradually from 1 day to 2 days in burns which is laser irradiation These data suggest that low power laser have a pain release effect in the burned skin of the rats.

• The Journal of Korean Physical Therapy
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• v.13 no.3
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• pp.569-578
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• 2001

The purpose of the present study was to examine the functional recovery of the crushed sciatic nerve of rats after low-power laser irradiation applied to the corresponding segments of the spinal cord. After a crushed injury on the left sciatic nerve in rats. low-power laser irradiation was applied transcutaneously to corresponding segments of the spinal cord immediately after suture the wound by using 2000 mW, 2000Hz, 830 nm CaAIAs(Gallium-aluminum-arsenide) semiconductor diode laser. The laser treatment was performed with 10 minutes daily for 4 successive weeks. Functional recovery was evaluated per weekly following injury by sciatic function index(SFI),using data obtained by walking track analysis. For four weeks after crush injury, experimental group had significantly greater functional improvement than control group(${\alpha}$=0.05). In a experimental group, SFI was significantly increased for three weeks, but control group not increased for two weeks. This study suggests that low-power laser irradiation applied directly to the spinal cord can improve functional recovery of the crushed sciatic nerve in rats.

• Journal of Periodontal and Implant Science
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• v.26 no.1
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• pp.230-243
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• 1996

Root surface exposure due to gingival recession after periodontal surgery, dentin exposure after root planing elicit pain response when exposed to mechanical, heat, chemical or osmotic stimulation. Especially, patients treated with periodontal surgery, show high frequency and there have been reports showing the 1 out of 7 patients have dentin hypersensitivity. There have been many studies on the clinical effects of various materials on the treatment of dentin hypersensitivity. but, none could provide absolute clinical efficacy. In this study, 45 teeth from 30 patients, who had had periodontal surgery and showed dentin hypersensitivity after surgery were chosen for the experimental group and they were illuminated with laser, 15teeth were chosen for the control group and they were not exposed to laser. After this dentin hypersensitivity was elicited by tactile, compressed air, cold water and then, the degree was evaluated using NRS(Numerical Rating Scale). And during LLLT(Low Level Laser Therapy) semiconductor laser using Gallium - Arsenide as a diode was illuminated for 180 seconds at a frequency of 7(500Hz). This therapy was done 10 times, and each time the changes in dentin hypersensitivity was evaluated using NRS. The results were as follows : 1. After treat with LLLT on dentin hypersensitivity due to periodontal surgery, 22.2% showed total loss of dentin hypersensitivity, 60.0% showed loss of tactile dentin hypersensitivity, 48.8% showed loss of compressed air dentin hypersensitivity, 22.2% showed loss of cold water dentin hypersensitivity. 2. As a result of clinical evaluation of dentin hypersensitivity using NRS, there was significant increase in improvement of dentin hypersensitivity in the experimental group compare to the control group(P<0.05). And there was almost no natural loss of dentin hypersensitivity in the control group. 3. In comparison of the stages of evaluation, there was significant difference in between experimental and control group. after the second visit(P<0.05), and the difference increased with each visit.

• The Journal of Korean Physical Therapy
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• v.14 no.3
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• pp.226-237
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• 2002

This study was performed to investigate the effect of low power laser irradiation on epidermal growth factor(EGF) expression in the burned skin of the rats. Burns of about 3cm in diameter were created with 75'c water on the back of the rats, and the lesion of experimental group were irradiated on days 1, 2, and 3 postwounding. Control tensions were not irradiated. After burns, low power laser irradiation was applied by using 1000Hz, 830nm GaAlAs (Gallium-aluminum- arsenide) semiconductor diode laser. The expression of epidermal growth factor evaluated immunohistochemistry on mouse anti-EGF. The results of this study were as follows 1. In expression of EGF, the lesion of experimental group made EGF to more induce significantly than control tensions. 2. EGF immunoreactivity in burned skin were increased markedly 3 days after burns, and increased gradually from 1 day to 2 days in burns which is laser irradiation These data suggest that low power laser have wound healing effect in the burned skin of the rats.

• Korean Journal of Optics and Photonics
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• v.17 no.6
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• pp.544-547
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• 2006

A time-domain modeling approach is used to study characteristics of a widely tunable coupled-ring reflector (CRR) laser diode(LD). The CRR consists of a bus waveguide and two coupled ring resonators coupled to the bus without resorting to distributed Bragg grating structure. The tuning range can be a few tens of nanometers with a side mode suppression ratio exceeding 35dB through the adjustment of currents into the phase control sections in the rings. The CRR laser diode has long effective cavity length compared to conventional laser diodes. Accordingly, a broad additional resonance peak in the amplitude modulation characteristics is observed between 20 to 30 GHz, implying the extension of amplitude modulation bandwidth.

• Journal of Oral Medicine and Pain
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• v.19 no.1
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• pp.33-43
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• 1994

The purpose of this paper was to observe the influence of Ga-As semiconductor-low power generating laser on she appearance and actions of tenascin, extracellular matrix, as healing process of intentional wound on the experimental animals is taking place. 35 rabbits were divided into control and experimental group. ; and on each, 3mm-long and 2mm-deep, surgical wounds were created on buccal oral mucosa and thoracodorsal portion of skin. Ga-As laser was applied to the experimental group starting a day of the day the wounds were created , the laser was applied for 5 minutes every other day. Tissue samples were taken after the 2, 4, 7, 10, and 14 days after wound formation. Then tile healing process of experimental and control groups were observed and compared, using light microscope. Afterwards, the samples were immunohistochemical stained and again observed tenascin by quantitative measuring. The following results were obtained : 1. Tenascin was observed prevalently on epithelial cells, border area of dermis, and interstitial matrix between connective tissue layers in both experimental and control groups. 2. In oral mucosa, the experimental group showed significant increase in the appearance of tenascin after 4 days compared to the control group, but after 10 days, it decreased to a point which is even less than the control group. 3. In the skin samples, the pattern of appearance of tenascin was the same in both groups, but there was some difference concerning when the peak period was shown, In the experimental group, the peak period of tenascin expression was the 7 days after wound formation in epithelium and connective tissue. In the control group, the peak period was 10 days after. 4. In both the experimental and control groups, tenascin first appeared in the epithelium near the wound area and submucosa, and then spread on the underlying connective tissue. In conclusion, appearance of tenascin is closely related to regeneration of epithelium and development of granulation tissue : therefore, low power laser, which fastnes appearance of tenascin, is sure to faciltate healing process of oral mucosa.