• Journal of the Optical Society of Korea
• /
• v.12 no.3
• /
• pp.192-195
• /
• 2008

We report on the spatial information of a coupling laser transfer into a reflected probe laser; the transfer is achieved by means of electromagnetically induced transparency through a common excited state connected with $5S_{1/2}-5P_{1/2}(F=1{\rightarrow}F'=2)$ in the $^{87}Rb\;D_1$ line. When the coupling laser was spatially modulated as a stationary wave, the absorption of the probe laser was enhanced and the reflection of the probe laser was generated. When the coupling laser was spatially modulated by a mask, we observed that the reflection light of the probe laser was modulated as the shape of the mask. The Bragg reflection transferred the spatial information of the coupling laser. The reflection was approximately 7% of the incident power of the probe laser.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.945-947
• /
• 2009

We developed a new laser irradiation (BLDA: Blue Multi-Laser-Diode Annealing) system. The system forms the uniform line beam, which is constructed by 48 pieces of semiconductor lasers. This new system has achieved high laser output stability and the highly accurate beam shape by adopting a reliable laser control, the auto-focus control in addition to an original laser photosynthesis technology and the beam homogenizing technology. It was confirmed to crystallize the Si films effectively with good quality.

• Current Optics and Photonics
• /
• v.2 no.5
• /
• pp.443-447
• /
• 2018

We propose a diode-pumped cesium laser using frequency locking of a pump laser that can effectively increase the maximum output power of the cesium laser. We simultaneously monitored the absorption spectrum of cesium and the laser output power, and the frequency of pump laser was locked at the center of the $D_2$ absorption line of the cesium atom to obtain an effective gain enhancement. Using this scheme, we have achieved output power increase of ~0.1 W compared to when frequency locking was not applied. Furthermore, by optimizing the temperature of the cesium cell and the reflectivity of the output coupler, we successfully achieved an output power of 1.4 W using the pump power of 2.9 W, providing a slope efficiency of 61.5% and optical-to-optical efficiency of 49%.

• Proceedings of the Optical Society of Korea Conference
• /
• 1991.06a
• /
• pp.64-64
• /
• 1991

The interaction of high-intensity, focused, nanosecond laser light with matter results in the production of high-temperature plasma, which in turn emits an intense pulse of x rays. The x-ray spectrum consists of strong line components of several keV photon energy and broad continuum. Such an x-ray source provides many advantages over conventional ones for many applications. Pulse nature of the x-ray emission is well-suited for studying transient phenomena and for imaging living biological specimen. Recent experiments have also shown that the laser plasma x ray may be used for x ray lithography. These studies and other applications will be discussed in detail.

• Journal of Welding and Joining
• /
• v.17 no.3
• /
• pp.26-35
• /
• 1999

On the laser weld production line, a slight alteration of the welding condition changes the bead size and the strength of the weldment. The measurement system is produced by using three photo-diodes for detection of the plasma and spatter signal in $CO_2$ laser welding. The relationship between the sensor signals of plasma or spatter and the bead shape, and the mechanism of the plasma and spatter were analyzed for the bead size estimation. The penetration depth and the bead width were estimated using the multiple regression analysis.

• Laser Solutions
• /
• v.13 no.4
• /
• pp.14-20
• /
• 2010

Robot path generation and laser welding technology for manufacturing automotive body are studied. Laser welding and industrial robot systems are used with the robot based laser welding system. The laser system used in this study is 1.6kW Fiber laser, while the robot system is 6 axes Industrial robot (payload: 130kg). The robot based laser welding system is equipped with laser scanner system for remote laser welding. The laser source, robot and laser scanner system are used to increase the processing speed and to improve the process efficiency. The welding joints of steel plate are butt and lapped joints. The quality test of the laser welding are through the observation the shape of bead on plate and cross-section of welding part. The 3 dimensional laser welding for non-linear pipe welding line is performed. This paper introduces the robot based laser welding system to resolve the limited welding speed and accuracy of the conventional spot welding system.

• Laser Solutions
• /
• v.8 no.1
• /
• pp.9-18
• /
• 2005

The laser direct writing method using a UV Argon-ion laser is studied for fabrication of waveguide. The laser direct writing system is constructed with a vision camera, a xy-stage, a motion controller and the delivery components of a laser beam. The UV Argon-ion laser has wavelength range of $333.6\~363.8$ nm. A photo-active UV curable polymer for a planar light-wave circuit(PLC) of single mode is used. This polymer is irradiated by Argon-ion laser and developed by a solvent after a post-baking. The optimum laser direct writing condition is obtained experimentally by changing various process parameters such as laser power, writing speed and focal length. The propagation and coupling loss of a optical waveguide was measured as 1dB/cm and 0.6dB/cm, respectively. Also, the minimum width of waveguide of $100{\mu}m$(ZPLW-207) is obtained. Finally, the waveguides of line, bend and branch type are successfully fabricated.

• Journal of the Korea Convergence Society
• /
• v.11 no.7
• /
• pp.157-162
• /
• 2020

In recent years, laser induced graphene process have been intensively studied for eco-friendly electronic device such as flexible electronics or thin film based energy storage devices because of its simple and effective process. In order to increase the performance and efficiency of an electronic device using such a graphene patterned structure, it is essential to study an optimized laser patterning condition as small as possible linewidth while maintaining the graphene-specific 2-dimensional characteristics. In this study, we analyzed to find the optimal line pattern by using a Ti:sapphire femtosecond laser based photo-thermal reduction process. we tuned intensity and scanning speed of laser spot for generating effective graphene characteristic and minimum thermal effect. As a result, we demonstrated the reduced graphene pattern of 30㎛ in linewidth by using a focused laser beam of 18㎛ in diameter.

• Korean Journal of Head & Neck Oncology
• /
• v.17 no.1
• /
• pp.3-7
• /
• 2001

Objectives: New photosensitizer 9-hydroxypheophorbide-$\alpha$(9-HpbD-$\alpha$) was derived from chlorophyll in water with peak absorption at 660nm. 9-HpbD-$\alpha$ was tested with 660 nm diode laser for the anticancer effect of photodynamic therapy. Materials and Methods: Human SNU 1041 cells were seeded into 96 well plate at a density of $$ cells/well for 24 hours. Cells were washed with media containing various concentration of 9-HpbD-$\alpha$ ranging from $0{\mu}g/ml\;to\;3.75{\mu}g/ml$. Then, laser treatment was done with 660nm diode laser ($10mW/cm^2$) at various time setting (0, 30, 60, 90, 120 minutes) and with various time interval (0, 1, 4, 6, 18 hours). The treated cells were incubated 48 hours and MTT assay was done to measure the viability of cells. Results: The viability of cells was more than 90% after laser treatment in control group. The viability of cells was decreased with increasing concentration of 9-HpbD-$\alpha$ and laser treatment time in experimental groups. The viability of cells was decreased significantly as the interval time between addition of 9-HpbD-$\alpha$ and laser irradiation was increased. Conclusion: This study shows the anticancer effect of photodynamic therapy using 9-HpbD-$\alpha$ and 660nm Diode laser on carcinoma cell line. 9-HpbD-$\alpha$ is considerd as one of new photo sensitizers in the field of photodynamic therapy.

• Journal of the Optical Society of Korea
• /
• v.13 no.1
• /
• pp.60-64
• /
• 2009

We attempted the first measurement of the spectral width of the nickel-like molybdenum x-ray laser (${\lambda}\;=\;18.895\;nm$) by use of a high-resolution spectrometer in order to determine the strength of the magnetic field required for the generation of a circularly polarized x-ray laser. The spectral width was measured to be ${\Delta}{\lambda}\;=\;18\;m{\AA}$ under the substantial lasing condition. The magnetic field required for the generation of a circularly polarized x-ray laser was 40 T. The splitting of the x-ray laser line was clearly obtained under 15 T external magnetic field. The strength of the magnetic field estimated from the splitting of the x-ray laser line was large compared with the external magnetic field. It implies that there might be an alternative mechanism for enhancement of the magnetic field in the gain medium plasma.