• Korean Journal of Optics and Photonics
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• v.20 no.5
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• pp.276-280
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• 2009

A Cr:YAG crystal was used as a saturable absorber for passive Q-switching of a Nd:$YVO_4$ laser which was pumped by a 1-W continuous wave laser diode. The first surface of the Cr:YAG was high-reflection coated for the pump wavelength. The high-reflection coating improved the absorption efficiency of the pump beam in the Nd:$YVO_4$ through double pass absorption. It also prevented pump beam induced partial bleaching of the Cr:YAG. The peak-to-peak pulse fluctuation of passively Q-switched laser output was approximately 4 %. The minimum pulse-width was measured to be 7.11 ns. Also, the average pulse repetition rate was 9 kHz and the maximum output power was 16.27 mW.

• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.311-317
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• 1999

Unidirectional single-mode operation of a diode-pumped Nd:YAG laser with a planar semimonolithic ring cavity has been demostrated at 1064 nm. The semimonolithic cavity consists of a laser active medium placed in a magnetic field, a crystal quartz plate, and an output coupling mirror. They form an optical diode by acting each part as a Faraday rotator, a reciprocal polarization rotator and a partial polarizer, respectively. An eigenpolarization theory for the cavity configuration was presented and losses for the eigenmodes were calculated. A pump-limited single-mode output power of 155 mW and a slope efficiency of 17% were obtained when the laser was pumped by a 1.2 W, 809 nm diode-laser. A laser linewidth of less than 100 kHz is inferred from a beat note frequency spectrum between two identical laser systems and continous single-mode tuning range was more than 2 GHz.

• Korean Journal of Optics and Photonics
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• v.32 no.2
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• pp.62-67
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• 2021

We have experimentally demonstrated sum-frequency generation (SFG) in a periodically poled lithium niobate (PPLN) crystal, using a mode-locked picosecond-pulsed fiber laser and a continuous-wave (CW) diode laser with a narrow linewidth. The mode-locked fiber laser had a center wavelength of 1560.7 nm and a spectral width of 1.1 nm, and the CW diode laser had a center wavelength of 1551.0 nm and a spectral width of 6 MHz. To effectively realize SFG, both of the spatial modes of the two lasers were made to overlap in the PPLN crystal by using a single-mode optical fiber. The pulse-mode SFG with pulsed- and CW-mode lasers was successfully observed in the spectral and time domains. These results are expected to be applicable in various ways, such as optical frequency measurement and high-resolution laser spectroscopy studies using optical frequency combs.

• Journal of Dental Anesthesia and Pain Medicine
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• v.22 no.1
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• pp.19-27
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• 2022

Background: Myofascial pain dysfunction syndrome (MPDS) is the most common type of temporomandibular disorder. This study compared the efficacies of low-level diode laser therapy (LLLT) and laser acupuncture therapy (LAT) in the treatment of MPDS. Methods: This double-blind randomized controlled clinical trial included 24 patients with MPDS who were randomly divided into two equally sized groups. Patients in the LLLT group received 12 sessions of low-level diode laser irradiation applied to the trigger points of the masticatory muscles during 1 month. The same protocol was also used in the LAT group according to the specific trigger points. We measured pain intensity and maximum mouth opening in both groups at baseline, during treatment, and 2 months after treatment completion. Results: The pain intensities decreased from 6.58±1.31 to 0.33±0.65 and from 7.08 ± 1.37 to 0 in the LLLT and LAT groups, respectively. The maximum mouth openings increased from 32.25 ± 8.78 mm to 42.58 ± 4.75 mm and from 33 ± 6.57 mm to 45.67 ± 3.86 mm in the LLLT and LAT groups, respectively. Pain intensity (P = 0.839) and level of maximum mouth opening (P = 0.790) did not differ significantly between the groups. Conclusion: Our results showed similar efficacy between LLLT and LAT in the treatment of MPDS signs and symptoms.

• Journal of Oral Medicine and Pain
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• v.23 no.4
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• pp.301-307
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• 1998

본 연구에서는 904nm의 다이오드 레이저를 발치창에 조사하여 효과를 분석하교, 동물실험에서 제시된 가설 즉 레이저 광조사가 주위정상조직을 자극하여 창상치유를 촉진하고 진통, 항염증효과가 있는지를 확인하고저 하였다. 먼저 19명의 발치환자에게 발치후 즉시 1분간 평균 14mW의 저수준레이저를 조사하였다. 이들중 8명은 대조군으로서 위조사(sham-irradiation)하였다. 일주일동안 시간경과에 따른 동통의 정도, 진통제의 사용횟수, 진통제 사용기간등을 각각조사하였다. Visual analogue scale로 두근에서 동통의 정도를 비교한 결과 대조군 보다 레이저 조사군에서 동통이 유의하게 감소하였으며, 진통제의 사용횟수가 기간도 레이저조사군에서 유의하게 감소하였다. 이러한 결과로 보아 비록 1분간의 적은 량의 레이저 조사라도 발치후 합병증을 억제하여 동통을 억제하고 치유를 촉진한다고 사료된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.121-121
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• 2013

최근 산업에서 이슈화되고 있는 고출력산업용레이저를 위한 반도체다이오드레이저 기술에 대한 산업적 관점을 소개하고자 한다. 열효율이 높고 및 비접촉 제어가 가능한 고출력다이오드에 대한 전반적인 소개와 함께, 왜 각광을 받고 있는지를 진단하며, 이러한 고출력레이저다이오드를 제작하는 방법에 관한 고찰을 하고자 한다. 특히 박막생성기술을 위한 장비 기술에 대해 소개하며, MBE와 MOCVD에 대해 비교하고자 한다. 실제적인 고출력레이저 다이오드제작을 위한 측정 및 신뢰성 기술에 대해서 소개하며, 한국광기술원에서 수행하고 있는 산업용 레이저 핵심부품 모듈 국산화 기반구축사업에 대한 소개를 하고자 한다. 한국광기술원 레이저 개발 내용 중 고출력다이오드레이저 개발을 위한 장비 소개 및 기술 소개를 하고자 한다.

• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.227-231
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• 2011

An external optical modulation using absorption s in a Fabry-Perot laser diode (FP-LD), has been proposed and experimentally demonstrated for multicasting in a WDM-PON. The center wavelengths of absorption s in an FP-LD move to short-wavelength rapidly by only a small current (~1 mA) injection. If the current injection is stopped, the s move back to the original position. Such a movement of the s can make the FP-LD act as an external optical modulator, which is found to modulate at a maximum modulation speed of 800 Mbps or more. For a multicasting transmitter in a WDM-PON, the proposed modulator can be cost-effectively applied to a multi-wavelength laser source with the same periodicity of the longitudinal mode. Instead of the multi-wavelength laser source, tunable-LDs are used for experiments. The 32 channel multicasting system with the proposed modulator has been demonstrated, showing power penalties of 1.53~4.15 dB at a bit error rate of $10^{-9}$ with extinction ratios better than 14.5 dB at 622 Mbps.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.1
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• pp.159-165
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• 1995

A double-heterostructure mesa-stripe-geometry laser diode integrated with thermoelectric Peltier cooler has been designed and fabricated. Epi-layers have been grown by metal organic chemical vapor deposition(MOCVD) method. Peltier cooling effect has been measured for devices with a mesa width of 14$\mu$m and a cavity length of 380$\mu$m. The effects of thermoelectric cooling could be shown by measuring the optical output of the laser with the increase of the current in the thermoelectric cooler. While the input courrent of the laser was maintained at 250mA, the optical output was decreased from 4.8mW to 3.8mW due to heating, but with the thermoelectric cooler on the optical output power was recovered by more than 40%. The results show that the complicated cooling device is not needed since the cooling can be achevied by the developement of the fabrication processing.

• Applied Microscopy
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• v.27 no.3
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• pp.257-263
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• 1997

Microstructural characterizations of II-VI blue laser diodes which consist of quaternary $Zn_{1-x}Mg_xS_ySe_{l-y}$ cladding layer, ternary $ZnS_ySe_{l-y}$ guiding layer and $Zn_{0.8}Cd_{0.2}Se$ quantum well as active layer were carried out using the transmission electron microscope working at 300 kV. Even though the entire structure is pseudomorphic to GaAs substrate, the structure had contained numerous extended stacking faults and dislocations which had created at ZnSe/GaAs interfaces and then further grown to the top of the epilayers. These faults might be expected to cause the degradation and shortening the lifetime of laser devices.

• Journal of the Optical Society of Korea
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• v.15 no.2
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• pp.124-127
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• 2011

Quantum dots were designed within a GRIN-SCH(Graded index - Separate confinement Heterostructure) heterostructure to create a high power InAlAs/AlGaAs laser diode. 808 nm light emission was with a quantum dot composition of In0.665Al0.335As and wetting layer composition of Al0.2Ga0.8As by LASTIP simulation software. Typical characteristics of GRIN structures such as high confinement ratios and Gaussian beam profiles were shown to still apply when quantum dots are used as the active media. With a dot density of 1.0x1011 dots/cm2, two quantum dot layers were found to be good enough for low threshold, high-power laser applications.