• KIEE International Transactions on Electrophysics and Applications
• /
• v.4C no.3
• /
• pp.96-100
• /
• 2004

The Nd： YAG laser is commonly used throughout many fields such as accurate material processing, IC marking, semiconductor annealing, medical operation devices, etc., due to the fact that it has good thermal and mechanical properties and is easy to maintain. In materials processing, it is essential to vary the laser power density for specific materials. The laser power density can be mainly controlled by the current pulse width and pulse repetition rate. It is important to control the laser energy in those fields using a pulsed laser. In this paper we propose the constant-frequency current resonant half-bridge converter and monitoring of capacitor charging voltage. This laser power supply is designed and fabricated to have less switching loss, compact size, isolation with primary and secondary transformers, and detection of capacitor charging voltage. Also, the output stabilization characteristics of this Nd： YAG laser system are investigated. The test results are described as a function of laser output energy and flashlamp arc discharging constant. At the energy storage capacitor charges constant voltage, the laser output power is 2.3％ error range in 600[V].

• Current Optics and Photonics
• /
• v.8 no.4
• /
• pp.382-390
• /
• 2024

Laser propagation through atmospheric disturbances is vital for applications such as laser optical communication, satellite laser ranging (SLR), laser guide stars (LGS) for adaptive optics (AO), and laser energy transmission systems. Beam degradation, including energy loss and pointing errors caused by atmospheric turbulence, requires thorough numerical analysis. This paper investigates the impact of laser beam parameters on ground-to-space laser propagation up to an altitude of 100 km using vertical atmospheric disturbance profiles from the Geochang SLR Observatory in South Korea. The analysis is confined to 100 km since sodium LGS forms at this altitude, and beyond this point, beam propagation can be considered free space due to the absence of optical disturbances. Focusing on a 100-watt class laser, this study examines parameters such as laser wavelengths, beam size (diameter), beam jitter, and beam quality (M²). Findings reveal that jitter, with an influence exceeding 70%, is the most critical parameter for long-exposure radius and pointing error. Conversely, M², with an influence over 45%, is most significant for short-exposure radius and scintillation.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.11a
• /
• pp.137-138
• /
• 2008

• Journal of the Optical Society of Korea
• /
• v.20 no.1
• /
• pp.78-87
• /
• 2016

Red blood cells (RBCs) are customarily adhered to a bio-functionalised substrate to make them stationary in interferometric phase-imaging modalities. This can make them susceptible to receive alterations in innate morphology due to their own weight. Optical tweezers (OTs) often driven by Gaussian profile of a laser beam is an alternative modality to overcome contact-induced perturbation but at the same time a steeply focused laser beam might cause photo-damage. In order to address both the photo-damage and substrate adherence induced perturbations, we were motivated to stabilize the RBC in OTs by utilizing a laser beam of ‘arbitrary intensity profile’ generated by a source having cavity imperfections per se. Thus the immobilized RBC was investigated for phase-imaging with sinusoidal interferograms generated by a compact and robust Michelson interferometer which was designed from a cubic beam splitter having one surface coated with reflective material and another adjacent coplanar surface aligned against a mirror. Reflected interferograms from bilayers membrane of a trapped RBC were recorded and analyzed. Our phase-imaging set-up is limited to work in reflection configuration only because of the availability of an upright microscope. Due to RBC’s membrane being poorly reflective for visible wavelengths, quantitative information in the signal is weak and therefore, the quality of experimental results is limited in comparison to results obtained in transmission mode by various holographic techniques reported elsewhere.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.1
• /
• pp.49-58
• /
• 1998

In this paper, a new equivalent circuit model for quantum-well laser diode (LD) is proposed. The model includes carrier transport effects in the SCH region, and rprovides, in a stable and accurate manner, large-and small-signal responses of laser diode output power as function of injected currents. SPICE simulation was performed using the circuit model and results are presented for L-I characteristics, pulse and frequency responses under various conditions. It is expencted that the new equaivalent circuit model will find useful applications for designing and analyzing OEIC, LD driver circuits, and LD packaging.

• Proceedings of the IEEK Conference
• /
• 1999.11a
• /
• pp.309-312
• /
• 1999

Fiber Bragg gratings have many applications such as fiber sensors, band-stop filters, add-drop filters, and mode convertors. In this paper, we present the fabrication method of various fiber Bragg gratings by using continuous wave UV-Argon(frequency-doubled Argon) laser. In our experiments, hydrogenation of fibers was used to enhance photosensitivity of fiber. And we fabricated fiber gratings by the phase mask method.

• Journal of Welding and Joining
• /
• v.22 no.2
• /
• pp.13-18
• /
• 2004

레이저 빔과 아크를 하나의 용접 프로세스로 병합하는 기술에 관해서는 이미 70년대부터 알려져 왔으나 별다른 개발로 이어지지 못하다가 최근에서야 다시 눈을 돌리게 되었다. 이 기술의 핵심 과제는 아크의 장점과 레이저의 장점을 어떻게 단일 혼합 프로세스로 조합하느냐 하는 것이다.(중략)

• Proceedings of the Optical Society of Korea Conference
• /
• 2003.02a
• /
• pp.42-43
• /
• 2003

The nonlinear three-wave interaction is an interesting topic having various applications in nonlinear optics, hydrodynamics, acoustic waves, and plasma physics. The resonant interaction between two laser pulses and a plasma wave plays important roles in plasma heating, laser reflection in the inertial confinement fusion (ICF), plasma wakefield generation, and ultra-intense laser pulse amplification and pulse compression using stimulated Raman backscattering (RBS). (omitted)

• Computers and Concrete
• /
• v.19 no.6
• /
• pp.701-710
• /
• 2017

In this study, the thermoelastic beam in modified couple stress theory due to laser source and heat flux is investigated. The beam are heated by a non-Guassian laser pulse and heat flux. The Euler Bernoulli beam theory and the Laplace transform technique are applied to solve the basic equations for coupled thermoelasticity. The simply-supported and isothermal boundary conditions are assumed for both ends of the beam. A general algorithm of the inverse Laplace transform is developed. The analytical results have been numerically analyzed with the help of MATLAB software. The numerically computed results for lateral deflection, thermal moment and axial stress due to laser source and heat flux have been presented graphically. Some comparisons have been shown in figures to estimate the effects of couple stress on the physical quantities. A particular case of interest is also derived. The study of laser-pulse find many applications in the field of biomedical, imaging processing, material processing and medicine with regard to diagnostics and therapy.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1540-1545
• /
• 2004

Measurement of concentration fields in a micro-channel is the crucial technology in the area of Lab-on-a-chip to be used for various bio-chemical applications. It is wel-known that the only possible way to measure the concentration field in the micro-channel is using micro-LIF(Laser Induced Fluorescence) method. However, an accurate concentration field at a given cross plane in a micro-channel has not been made so far due to the limit of light illumination. The present study demonstrates a novel method to provide an ultra thin laser sheet beam having 5 microns thickness by a micro focus laser line generator. Nile Blue A was used as fluorescent dye for LIF measurement. The laser sheet beam illuminates an exact plane of concentration measurement in the micro-channel to increase the signal to noise ratio and reduce the depth uncertainty considerably.