• 한국레이저가공학회지
• /
• 제8권2호
• /
• pp.7-12
• /
• 2005

The material processing of UV nanosecond pulse laser cannot be avoided the material shape change and contamination caused by interaction of base material and laser beam. Nowadays, ultra short pulse laser shorter than nanosecond pulse duration is used to overcome this problem. The advantages of this laser are no heat transfer, no splashing material, no left material to the adjacent material. Because of these characteristics, it is so suitable for micro material processing. The processing of sapphire wafer was done by UV 355nm, green 532nm, IR 1064nm. X-Y motorized stage is installed to investigate the proper laser beam irradiation speed and cycles. Also, laser beam fluence and peak power are calculated.

• Journal of Advanced Marine Engineering and Technology
• /
• 제20권5호
• /
• pp.93-102
• /
• 1996

Laser-induced plume and laser-target interaction during pulsed laser deposition are demonstrated for a lead zirconate titanate (PZT). A KrF excimer laser (wavelength 248nm) was used and the laser was pulsed at 20Hz, with nominal pulse width of 20ns. The laser fluence was~$16J/cm^2,$ with 100mJ per pulse. The laser-induced plasma plume for nanosecond laser irradiation on PZT target has been investigated by optical emission spectra using an optical multichannel analyzer(OMA) and by direct observation of the plume using an ICCD high speed photography. OMA analysis showed two distinct ionic species with different expansion velocities of fast or slow according to their ionization states. The ion velocity of the front surface of the developing plume was about $10^7$cm/sec and corresponding kinetic energy was about 100eV. ICCD photograph showed another kind of even slower moving particles ejected from the target. These particles considered expelled molten parts of the target. SEM morphologies of the laser irradiated targets showed drastic melting and material removal by the laser pulse, and also showed the evidence of the molten particle ejection. The physics of the plasma(plume) formation and particle ejection has been discussed.

• Journal of Mechanical Science and Technology
• /
• 제19권5호
• /
• pp.1116-1122
• /
• 2005

A finite element method was used to simulate the wave propagation of laser-generated ultrasound and its interaction with surface breaking cracks in an elastic material. Thermoelastic laser line source on the material surface was approximated as a shear dipole and loaded as nodal forces in the plane-strain finite element (FE) model. The shear dipole- FE model was tested for the generation of ultrasound on the surface with no defect. The model was found to generate the Rayleigh surface wave. The model was then extended to examine the interaction of laser generated ultrasound with surface-breaking cracks of various depths. The crack-scattered waves were monitored to size the crack depth. The proposed model clearly reproduced the experimentally observed features that can be used to characterize the presence of surface-breaking cracks.

• 한국정밀공학회지
• /
• 제28권12호
• /
• pp.1359-1365
• /
• 2011

The changes of ablation characteristics with respect to laser parameters and material parameters during pulsed laser ablation of solids were discussed with experimental results. Although laser wavelength, laser pulse width, and laser pulse energy are the primary factors to be considered, it is shown that other parameters such as laser spot size and material properties also critically influence on the ablation results. It is further demonstrated that the microstructural characteristics of the target can lead to completely different ablation rate and surface morphology.

• 한국정밀공학회지
• /
• 제27권2호
• /
• pp.7-12
• /
• 2010

Due to the extremely short interaction time (< $10\times10^{-12}$sec) between laser pulse and material, which enables the minimization of heat affection, ultrafast laser micro-machining has rapidly widened its applications. In this paper, the characteristics of ultrafast laser micro-machining have been reviewed and experimentally demonstrated in laser drilling of silicon wafer and in laser cutting of rigid PCB.

• Current Optics and Photonics
• /
• 제8권2호
• /
• pp.138-150
• /
• 2024

This study is essential for advancing our knowledge about the interaction between long-range high-power lasers and energetic materials, with a particular emphasis on understanding the response of a 155-mm shell under various surface irradiations, taking into account external factors such as atmospheric disturbances. The analysis addresses known limitations in understanding the use of non-realistic targets and the negligence of ambient conditions. The model employs the three-dimensional level-set method, computer-aided design (CAD)-based target design, and a message-passing interface (MPI) parallelization scheme that enables rapid calculations of the complex chemical reactions of the irradiated high explosives. Important outcomes from interaction modeling include the accurate prediction of the initiation time of ignition, transient pressure, and temperature responses with the location of the initial hot spot within the shell, and the relative magnitude of noise with and without the presence of physical ambient disturbances. The initiation time of combustion was increased by approximately a factor of two with atmospheric disturbance considered, while slower heating of the target resulted in an average temperature rise of approximately 650 K and average pressure increase of approximately 1 GPa compared to the no ambient disturbance condition. The results provide an understanding of the interaction between the high-power laser and energetic target at a long distance in an atmospheric condition.

• 한국레이저가공학회:학술대회논문집
• /
• 한국레이저가공학회 2001년도 춘계학술발표대회 논문개요집
• /
• pp.55-58
• /
• 2001

• 한국레이저가공학회지
• /
• 제4권2호
• /
• pp.13-19
• /
• 2001

When a high-power laser beam is irradiated on the surface of material, it is well known that a cavity, called a keyhole induced by the pressure action of the vapor plume, is generated in the molten material. This paper describes the interaction between a pulsed CO$_2$ laser beam and water. The laser-beam is used to generate and maintain a conical depression in the water surface similar to the keyhole created during laser penetration welding. Experimental results show that the depth of laser-beam penetration is limited by hydrodynamic instability. The instability of the surface cavity can be understood by the capillary instability of a hollow jet. Theoretical computation of the steady keyhole shape has been performed. modifying the model suggested by Andrews et al. (1976). The model predicts the qualitative behavior of the keyhole but significantly underestimates the average diameter.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2006년도 춘계학술대회 논문집
• /
• pp.163-164
• /
• 2006

In this paper, an analytical laser ablation model with Maxwell equation will be addressed by considering relationship between laser ablation and material. The Maxwell equation consists of four equations: two Gauss laws for electric and magnetic fields, Faraday's law, and Ampere's law. This analytical model will be calculated by employing Finite Difference Time Domain (FDTD). This method also makes it possible to simulate the laser beam propagation in a wide range of materials, such as metals, semiconductors, and dielectrics. Therefore, in this study, a numerical model for short pulse laser interaction with materials is developed, focusing on the accurate description of laser beam propagation and ablation process into the material with each pulse.

• 한국레이저가공학회:학술대회논문집
• /
• 한국레이저가공학회 2004년도 추계학술대회논문집
• /
• pp.22-28
• /
• 2004

Pit and rim formation on the Acrylonitrile Butadiene Styrene(ABS) plastic surface was evaluated after it was irradiated by $CO_2$ and Nd:YAG laser beams. Our results show that thermal effect floor was well observed at the outer wall of pit with $CO_2$ laser irradiated while it was not the case with Nd:YAG laser irradiated. Also the volume and depth of pit formation increase proportionally with the energy intensities of two laser irradiations, but there are significant differences in the slope, width, and FWHM of the Pit formation with two types of laser irradiations. This result shows that $CO_2$ laser irradiation leads to better cooling contraction effect while Nd:YAG laser irradiation induces better recoil pressure effect during the interaction between ABS plastic and laser beam irradiation. The shape of the laser marking could vary significantly depending on the traveling path of molten plastic during injection molding of ABS plastic. Therefore, the selection of material and molding process can have a great impact on the performance of optical storage media.