• Current Optics and Photonics
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• 제7권1호
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• pp.1-14
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• 2023

Wavefront-coding imaging can achieve high-quality imaging along with a wide range of defocus. In this paper, the anti-laser detection and damage performance of wavefront-coding imaging systems using different asymmetric phase masks are studied, through modeling and simulation. Based on FresnelKirchhoff diffraction theory, the laser-propagation model of the wavefront-coding imaging system is established. The model uses defocus distance rather than wave aberration to characterize the degree of defocus of an imaging system. Then, based on a given defocus range, an optimization method based on Fisher information is used to determine the optimal phase-mask parameters. Finally, the anti-laser detection and damage performance of asymmetric phase masks at different defocus distances and propagation distances are simulated and analyzed. When studying the influence of defocus distance, compared to conventional imaging, the maximum single-pixel receiving power and echo-detection receiving power of asymmetric phase masks are reduced by about one and two orders of magnitude respectively. When exploring the influence of propagation distance, the maximum single-pixel receiving power of asymmetric phase masks decreases by about one order of magnitude and remains stable, and the echodetection receiving power gradually decreases with increasing propagation distance, until it approaches zero.

• Current Optics and Photonics
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• 제6권3호
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• pp.282-287
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• 2022

Narrowing the spectral linewidth and improving the wavelength stability of high-power laser diodes (HPLDs) are both in high demand for rapidly maturing industrial laser applications. In this study, we investigate the spectral behavior of a commercial HPLD bar module composed of 19 laser diodes (LDs) in a single-layered bar with a built-in volume Bragg grating (VBG) and an additional cascaded VBG. Optical loss due to the extra cascaded VBG is kept below 5% when the optical output is 5 W or more. The full width at half maximum of the Fabry-Perot peak from the cascaded VBG is reduced to about 12.4% and 29.1% at the edge (1^st LD) and center (10^th LD) of the HPLD bar module respectively, compared to using only a built-in VBG at an optical power of 10 W or more. In addition, fine wavelength tuning is achieved by temperature control of the extra VBG, and the obtained wavelength-tuning range amounts to about 10.6 pm/K.

• 대한임베디드공학회논문지
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• 제11권6호
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• pp.379-392
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• 2016

This paper presents the design and simulation of a laser power beaming (LPB) system for an electric vehicle that establishes an optimal power transmission path based on the received signal strength. The LPB system is possible to transfer power from multiple transmitters to a single receiver according to the characteristics of the laser and the solar panel. When the laser beams of multiple transmitters aim at a solar panel at the same time, the received power is the sum of all energy at a solar panel. Our proposed LPB system consists of multiple transmitters and multiple receivers. The transmitter sends its power characteristics as optically coded pulses with a class 1 laser beam and powers as a high-intensity laser beam. By using the attenuated power level, the receiver can estimate the maximum receivable powers from the transmitters and select optimal transmitters. Throughout the simulation, we verified the possibility that different LPB receivers were achieved their required power by the optimal allocation of the transmitter among the various transmitters.

• Current Optics and Photonics
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• 제5권3호
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• pp.306-310
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• 2021

A 200-W continuous-wave thulium-doped all-fiber laser at 2050 nm was developed with a master oscillator power amplifier configuration. For the master oscillator, a single-mode thulium-doped fiber laser was built with fiber Bragg gratings. The operating power of the oscillator was 10.1 W at a pump power of 20.9 W, and the slope efficiency was measured to be 53.0%. All emitted wavelengths of the oscillator were located between 2049.2 nm and 2049.9 nm, and no other peaks in different wavelength ranges were observed. The maximum output power of the final amplified beam was 204.6 W at a pump power of 350.4 W. The slope efficiency of the amplifier was measured to be 58.4%.

• 전기학회논문지
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• 제62권6호
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• pp.798-802
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• 2013

In a conventional DC power supply used for CO2 laser, the circuit elements such as a rectifier bridge, a current-limiting resistor, a high voltage switch, energy storage capacitors ans a high-voltage isolation transformer using high turn ratio are necessary. Consequently, those supplies are expensive and require a large space. Thus, laser resonator and power supply should be optimally designed. In this paper, we propose a new power supply using high frequency resonance phenomena for CW(Continuous wave) CO2 laser (maximum output of 23W with discharge length of 450mm). It consists of a transformer including leakage inductance, magnetizing inductance and half-bridge converter, a three-stage Cockcroft-Walton and PFC(Power factor correction) circuit. The output ripple voltage can be controlled the minimum of 0.24% under the high frequency switching of 231kHz. Furthermore, the output efficiency was improved to 16.4% and the laser output stability of about 5.6% was obtained in this laser system.

• Journal of Welding and Joining
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• 제17권1호
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• pp.71-76
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• 1999

The real-time holographic interferometer with digital high-speed camera is applied to the experimental study of laser induced plasma/plume in pulsed Nd:YAG laser welding. A pulsed Nd:YAG laser with 1.2 kW average power is applied to generate laser induced plume. The recording speed of the high-speed camera is 3,000 f/s. The high speed photographs of weld plume without another visualization method, are compared with the visualization photographs with holographic interferometer. The radiation intensity from the laser induced plume is recorded by the high speed photographs, which fluctuated during laser radiation and disappeared after laser end. The density distribution of the plume is recorded by the holographic visualization method. The experimental results show the process of generation of the laser induced plasma/plume, and give the feasibility of quantitative measurement of laser induced plume in laser welding.

• 한국정밀공학회지
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• 제22권9호
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• pp.34-40
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• 2005

Laser welding of thermoplastics is a new jointing technique with a host of advantages. It is not only another extremely useful welding method but also a cost-effective alternative to traditional techniques involving screws or adhesives. Transmission laser-welding of thermoplastics such as polycarbonate(PC), polypropylene(PP), polyvinyl chloride(PVC), low density polyethylene(LDPE) and acrylic using a high power diode laser has been studied experimentally. The optical transmission of each plastic has been measured at laser wavelength of 808nm. The weld process has been characterized by the specific energy and weld time required for each plastic. The characteristics of laser welding between same plastics have also been analyzed.

• Current Optics and Photonics
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• 제1권5호
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• pp.525-528
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• 2017

High-energy, high-power, quasi-continuous wave (QCW) operation of double-clad Yb fiber lasers incorporating an incoherent signal combiner is reported. We constructed four efficient, high-power Yb fiber lasers, each of which produced rectangular pulses at 1080 nm with a pulse energy greater than 15 J, and a pulse duration of 10 ms at a repetition rate of 10 Hz, corresponding to an average power of over 150 W and a peak power of over 1.5 kW for ~200 W of incident pump power at 915 nm. These laser outputs were combined by a homemade incoherent fiber signal combiner with low loss, yielding a maximum peak power of ~6.0 kW in a beam with $M^2{\approx}12.5$. The detailed laser characteristics and prospects for further power scaling in QCW operation are discussed.

• Journal of the Optical Society of Korea
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• 제13권4호
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• pp.416-422
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• 2009

We have demonstrated a highly efficient cladding-pumped ytterbium-doped fiber laser, generating $>$2.1 kW of continuous-wave output power at 1.1 μm with 74% slope efficiency with respect to launched pump power. The beam quality factor ($M^2$) was better than 1.2. The maximum output power was only limited by available pump power, showing no evidence of roll-over even at the highest output power. We present data on how the beam quality depends on the fiber parameter, based on our current and past fiber laser developments. We also discuss the ultimate power-capability of our fiber in terms of thermal management, Raman nonlinear scattering, and material damage, and estimate it to 10 kW.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.319-321
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• 2004

We report on progress in developing high-power excimer lasers as well as UV-optics for creating low-temperature poly silicon (LTPS). A new high-power excimer laser offers 315 Watts with high pulse to pulse energy stability. Larger substrates can now be processed in better quality with either the SLS process or the new optics for line beam excimer laser annealing.