• Current Optics and Photonics
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• v.1 no.4
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• pp.271-277
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• 2017

Based on the extended Huygens-Fresnel principle, the analytical propagation formulae for spectrally partially coherent Gaussian Schell-model pulsed (SPGSMP) beams propagating in turbulent atmosphere have been derived. The influences of the parameters for turbulent atmosphere and SPGSMP beams on the on-axis and off-axis spectral shift and degree of coherence for SPGSMP beams propagating in turbulent atmosphere have been analyzed, using numerical calculations. The obtained results have potential applications for SPGSMP beams in free-space optical communication and laser lidar.

• Laser Solutions
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• v.16 no.3
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• pp.27-31
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• 2013

To engrave high-density circuit-line patterns in IC substrates, we applied a projection ablation technique in which a dielectric ($ZrO_2/SiO_2$) mask, a DPSS UV laser instead of an excimer laser, a refractive beam shaping optics and a galvo scanner are used. The line/space dimension of line patterns of the dielectric mask is $10{\mu}m/10{\mu}m$. Using a ${\pi}$ -shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam; and a telecentric f-${\theta}$ lens focuses it to a $115{\mu}m{\times}105{\mu}m$ flat-top beam on the mask. The galvo scanner before the f-${\theta}$ lens moves the beam across the scan area of $40mm{\times}40mm$. An 1:1 projection lens was used. Experiments showed that the widths of the engraved patterns in a buildup film ranges from $8.1{\mu}m$ to $10.2{\mu}m$ and the depths from $8.8{\mu}m$ to $11.7{\mu}m$. Results indicates that it is required to increase the projection ratio to enhance profiles of the engraved patterns.

• Laser Solutions
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• v.16 no.4
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• pp.1-6
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• 2013

Femtosecond laser patterning of ITO on a touch screen panel with a shaped fs laser beam was investigated. A quasi flat-top beam was formed using a variable mask and a planoconvex lens. The spatial profile of the original Gaussian beam and the shaped beam were monitored by a CCD beam profiler. The laser patterned ITO film was examined using an optical microscope, Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), and Atomic Force Microscope (AFM). It turned out that the quality of the ITO pattern fabricated by a shaped beam is superior to that of the pattern without beam shaping in terms of debris generation, height of the craters, and homogeneity of the bottom. Optimum processing window was determined at the laser irradiance exhibiting 100% removal of Sn. The removal rate of In was measured to be 83%.

• Laser Solutions
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• v.16 no.2
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• pp.1-6
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• 2013

Picosecond lasers are a very effective tool for micromachining metals, especially when high accuracy, high surface roughness and no heat affected zone are required. However, low productivity has been a limit to broadening the spectrum of their industrial applications. Recently it was reported that in the micromachining of copper with a 1064nm picosecond laser, there exist the optimal pulse energy and repetition rate to achieve the maximum volume ablation rate. In this paper, we used a 515nm picosecond laser, which is more efficient for micromachining copper in terms of laser energy absorption, to obtain its optimal pulse energy and repetition rate. Theoretical analysis based on the experimental data on copper ablation showed that using a 515nm picosecond laser instead of a 1064nm picosecond laser is more favorable in that the calculated threshold fluence is 75% lower and optical penetration depth is 50% deeper.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.216-221
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• 2017

Reducing optical reflection in the visible light range, in order to increase the share of transmitted light and avoid the formation of ghost images in imaging, is important for polymer lens applications. In this study, polymer lenses with refractive indices of n=1.56, 1.60, and 1.67 were fabricated by the injection-molding method with a polymer lens monomer, dibutyltin dichloride as the catalyst and an alkyl phosphoric ester as the release agent. To investigate their anti-reflection (AR) effects, various AR coating structures, viz. a multi-layer AR coating structure, tri-layer AR coating structure with a discrete approximation Gaussian gradient-index profile, and tri-layer AR coating structure with a quarter-wavelength approximation, were designed and coated on the polymer lens by an E-beam evaporation system. The optical properties of the polymer lenses were characterized by UV-visible spectrometry. The material properties of the thin films, refractive index and surface roughness, were analyzed by ellipsometry and AFM, respectively. The most effective AR coating structure of the polymer lens with low refractive index, n=1.56, was the both side coating of multi-layer AR coating structure. However, both side coating of the tri-layered discrete approximation Gaussian gradient-index profile AR coating structure gave comparable results to the both side coating of the multi-layer AR coating structure for the polymer lens with a high refractive index of n=1.67.

• Current Optics and Photonics
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• v.8 no.4
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• pp.406-415
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• 2024

The major error factors that degrade the efficiency of coherent beam combining (CBC) are numerically studied in a comprehensive manner, paying particular attention to phase, tip-tilt, polarization angle, and beam quality. The power in the bucket (PIB), normalized to the zero-error PIB, is used as a figure of merit to quantify the effect of each error factor. To maintain a normalized PIB greater than or equal to 95% in a 3-channel CBC configuration, the errors in phase, tip-tilt, and polarization angle should be less than 1.06 radians, 1.25 ㎛, and 1.06 radians respectively, when each of the three parameters is calculated independently with the other two set to zero. In a worst-case scenario of the composite errors within the parameter range for the independent-95%-normalized-PIB condition, the aggregate effect would reduce the normalized PIB to 83.8%. It is noteworthy that the PIB performances of a CBC system, depending on phase and polarization-angle errors, share the same characteristic feature. A statistical approach for each error factor is also introduced, to assess a CBC system with an extended number of channels. The impact of the laser's beam-quality factor M² on the combining efficiency is also analyzed, based on a super-Gaussian beam. When M² increases from 1 to 1.3, the normalized PIB is reduced by 2.6%, 11.8%, 12.8%, and 13.2% for a single-channel configuration and 3-, 7-, and 19-channel CBC configurations respectively. This comprehensive numerical study is expected to pave the way for advances in the evaluation and design of multichannel CBC systems and other related applications.

• ETRI Journal
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• v.21 no.3
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• pp.41-48
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• 1999

We have calculated differential reflection coefficient for isolated well structure of micro-scale, etched on dielectric surface. The differential reflection coefficient is computed using Green's second integral theorem. The purpose of our computation is to find a class of well profiles which give maximal diffusive scattering. To have such a maximal effect, we have concluded that the waist radius of Gaussian beam and its wavelength should be comparable to the well width and that well depth has to be larger than a wavelength. Exact calculation of differential reflection coefficients of dielectric surface with isolated structure on it may be used for the examination of dielectric surfaces and also in making simple but efficient diffuser.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.157-161
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• 1990

Self-pumped phase conjugation(SPPC) in BaTiO3 single crystal is experimentally investigated at a wavelength of 514.5nm from an Ar+ laser. The incident Gaussian beam enters the crystal as an extraordinary ray. The maximum SPPC reflectivity of 48% is obtained at incident angle 80 degree. the SPPC wave demonstrates good image reconstruction. The response time (r) of SPPC wave as a function of incident intensity is measured to be r=36$\times$I-0.79sec.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1157-1159
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• 2003

The effect of the scan velocity modulation is studied. The effect of the velocity modulation on the picture image is judged from the intensity profile of the image. The intensity profile is obtained as time integral of moving Gaussian beam. To confirm the applicability of this integral formula, the measurement and simulation data is compared. And by calculating the intensity profile for different amounts of velocity modulation, the optimum modulation displacement that gives the best image quality is obtained. This optimum modulation displacement can be used in designing scan velocity modulation system.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.359-361
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• 1993

The force exerted on particles when the momentum of light is changed at the boundary is used in accelerating particles in the fluid. So far, particles are accelerated by the gaussian beam focused by lenses or microscopic objectives. In this paper, particles arc moved by the light diffracted from the fiber end. And we proposed the possibility of particle acceleration using the fiber end.