• Journal of the Optical Society of Korea
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• v.8 no.1
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• pp.13-16
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• 2004

A widely tunable SG-DFB (Sampled Grating Distributed Feedback) laser diode is proposed and its feasibility is confirmed through simulation. The new SG-DFB laser diode is composed of a pair of sampled gratings, some parts of which are gain sections and the other parts of which are phase control sections. It is shown that a few tens of nanometers can be tuned through the adjustment of two currents into the phase control sections. Higher output power is expected compared with a SG-DBR laser diode with similar parameters. The dynamic single mode operation is also observed in the time-domain simulation.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.80-84
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• 2007

We propose a new displacement measurement method using a phase modulation homodyne interferometer and a tunable laser diode as a light source to determine an arbitrary length with a resolution in the order of 10 pm. In the proposed instrument, the displacement of a movable mirror in the interferometer can be converted to a frequency shift of the tunable laser diode. We discuss the principles of the proposed method, the instrumentation, and the experimental results, and compare the proposed method with two commercial displacement sensors. The commercial sensors used are a heterodyne interferometer, the interpolation error of which is also measured, and a capacitive sensor.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.04a
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• pp.846-851
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• 2000

4-state 바코드의 정보는 우편번호, 배달순서코드, 고객 정보 등을 수록되며, 판독율 향상을 위한 오류정정 코드워드를 적용할 수 있다. 이 4-state 바코드는 우편물 자동구분처리의 효율화 및 우편물류의 정보표현, 전달, 처리를 효율적으로 지원되도록 개발하고 있다. 본 논문은 우편물 접수 및 처리과정에서 필요로 하는 4-state 고객 바코드 인쇄규격 검증 및 판독시스템 개발에 관한 것으로 4개의 높이로 구성된 바들의 특성과 바의 두께 및 공간 값이 균일한 간격으로 바가 인쇄되는 특징을 고려하여 Laser Diode 배열방법을 적용하였다. 또한, 우편물을 자동으로 이송시키고, 일정한 영역에 배열한 Laser Diode에 의하여 바의 두께, 공간, 높이 값을 정확하게 판독될 수 있도록 한 것이다.

• Journal of the Optical Society of Korea
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• v.14 no.1
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• pp.38-41
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• 2010

We design and fabricate a widely tunable laser diode made of InGaAsP-InP. The diode is monolithically integrated with a wavelength-selective coupled-ring reflector and semiconductor amplifiers. For realization of a compact size device, deeply etched multi-mode interference couplers and square ring resonators composed of total-internal-reflection mirrors are adopted and fabricated using a self-aligned process. It is demonstrated that the laser diode exhibits single mode operation and 16 nm tuning range with side-mode-suppression-ratio exceeding 20 dB.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.7
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• pp.65-72
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• 2009

Laser interferometry is widely used as a measuring system in many fields because of its high resolution and its ability to measure a broad area in real-time all at once. In conventional laser interferometry, for example out-of-plane ESPI (Electronic Speckle Pattern Interferometry), in plane ESPI, shearography and holography, it uses PZT or other components as a phase shift instrumentation to extract 3-D deformation data, vibration mode and others. However, in most cases PZT has some disadvantages, which include nonlinear errors and limited time of use. In the present study, a new type of laser interferometry using a laser diode is proposed. Using Laser Diode Sinusoidal Phase Modulating (LD-SPM) interferometry, the phase modulation can be directly modulated by controlling the laser diode injection current thereby eliminating the need for PZT and its components. This makes the interferometry more compact. This paper reports on a new approach to the LD (Laser Diode) Modulating interferometry that involves four-frame phase shift method. This study proposes a four-frame phase mapping algorithm, which was developed to have a guaranteed application, to stabilize the system in the field and to be a user-friendly GUI. In this paper, the theory for LD wavelength modulation and sinusoidal phase modulation of LD modulating interferometry is shown. Using modulating laser and research of measurement algorithm does comparison with existent ESPI measurement algorithm. Algorithm measures using GPIB communication through most LabVIEW 8.2. GPIB communication does alteration through PC. Transformation of measurement object measures through modulating laser algorithm that develops. Comparison of algorithm of modulating laser developed newly with existent PZT algorithm compares transformation price through 3-D. Comparison of 4-frame phase mapping, unwrapping, 3-D is then introduced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.411-411
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• 2009

Low level laser therapy has various therapy effects. This paper performed the basic study for developing the Low Level Laser Therapy Equipment for medical treatment. The apparatus has been fabricated using the laser diode and microprocessor unit. This equipment was fabricated using a micro-controller and a laser diode, and designed to enable us to control light irradiation time, frequency and so on. In this study, the designed device was used to find out how infrared laser diode affected the collagen formation. For in-vivo test, a round wound 1cm in diameter was cut from the test animal whose epidermal and dermal layers were removed. Test animals were relieved for 24 hours after wounds had been excised and then the infrared laser irradiation group was given irradiation therapy over 9 days one 20 min per day. As a result, More collagenosis occurred in the order of infrared laser irradiation and non-irradiation group. Collagenosis is closely related to wound repair and it was found that infrared laser irradiation groups had more collagenosis and was quicker to recover from wound than non-irradiation group.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.3
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• pp.38-49
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• 1998

The 3rd generation optical pick-up used popularly in resent years is composed of many optical and electronic components such as laser diode, photo diode, beam splitter, objective lens, grating lens, concave lens, collimator lens etc. Therefore, the design of its optical system and its main base which the said optical and electronic components are set on, is complicated and needs high precision. Its assembly and adjustment in the production line is also difficult. This complication and the demand of high precision get its production cost to be high and its reliability to be low. In this paper, the 4th generation optical pick-up is designed and developed, with the hologram device which laser diode. photo diode, beam splitter. and grating lens are integrated in. This optical pick-up reduces the number of points of adjustment by 3, compared with the 3rd generation optical pick-up of which the number of points of adjustment is 6. This optical pickup also decreases by 4 the number of points of W bonding to have bad influence on environmental reliability, decreases by about 10 the number of parts, and establishes about 20% cost-down of material cost, compared with the 3rd generation optical pick-up.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.93-100
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• 2008

Laser interferometry is widely used as a measuring system in many fields because of its high resolution and ability to measure a broad area in real-time all at once. In conventional LASER interferometry, for example Out-of-plane ESPI(Electronic Speckle Pattern Interferometry), In plane ESPI, Shearography and Holography, it uses PZT or other components as a phase shift instrumentation to extract 3D deformation data, vibration mode and others. However, in most cases PZT has some disadvantages, which include nonlinear errors and limited time of use. In the present study, a new type of LASER interferometry using a laser diode is proposed. Using LASER Diode Sinusoidal Phase Modulating (LD-SPM) interferometry, the phase modulation can be directly modulated by controlling the LASER Diode injection current thereby eliminating the need for PZT and its components. This makes the interferometry more compact. This paper reports on a new approach to the LD Modulating interferometry that involves four-buckets phase shift method. This study proposes a four-bucket phase mapping algorithm, which was developed to have a guaranteed application, to stabilize the system in the field and to be a user-friendly GUI. In this paper, the theory for LD wavelength modulation and sinusoidal phase modulation of LD modulating interferometry is shown. Four-bucket phase mapping algorithm is then introduced.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.292-297
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• 2003

A diode-pumped single-mode Nd:YV $O_4$ green laser was developed. Frequency doubling of the laser was achieved by using an intracavity KTP generated green beam (532 nm). By comparing the diode laser spectrum with absorption spectrum of the Nd:YV $O_4$ crystal, we found optimal operating temperature of the diode laser. From output power measured for various mirror curvatures and cavity lengths, we found the optimal matching of TE $M_{00}$ mode with the pump beam gives the best efficiency. When the pump power was 1.9 W, 80 ㎽ of TE $M_{00}$ mode green beam was obtained. We tried to get a single longitudinal mode lasing as the fluctuation of the laser power was caused by the shift of longitudinal modes and the beating between the modes. We tested the intracavity etalon method and birefringent filter method for single mode operation. The etalon method resulted in the best single mode output power of 60 ㎽. The power fluctuation of the single-mode laser was reduced to 1/10 of that of the multi-mode laser.

• Current Optics and Photonics
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• v.4 no.2
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• pp.127-133
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• 2020

We successfully constructed a passively Q-switched Yb:YAG laser ignitor pumped by a diode laser with low power and long pulse width. To the best of our knowledge, this is the first study to achieve a quasi-MW output power from an optimized Q-switch Yb:YAG laser ignitor by using a pumping diode laser module emitting at under a power of 23 W. The output pulse energy of our optimized laser is 0.98 mJ enclosed in a 1.06 ns pulse width, corresponding to a peak power of 0.92 MW.