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Erratum: Laser-Induced Graphite Plasma Kinetic Spectroscopy under Different Ambient Pressures (Chinese Physics Letters (2015) 32:4 043201)
(2015-06-01)
Chaudhary, K.
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Rosalan, S.
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Aziz, M. S.
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Bahadoran, M.
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Ali, J.
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Laser-induced graphite plasma kinetic spectroscopy under different ambient pressures
(2015-04-01)
Chaudhary, K.
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Rosalan, S.
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Aziz, M. S.
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Bohadoran, M.
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Ali, J.
The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Ablation and excitation of the graphite material is performed by using an 1064nm Nd:YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emission. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations.
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Kinetic model for carbon species distribution in arc discharge plasma
(2015-01-12)
Roslan, M. S.
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Chaudhary, K.
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Aziz, M. S.
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Ali, J.
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Yupapin, P. P.
In present work, numerical integration for density distribution of carbon species in arc discharge plasma is presented. The model incorporates two-body collision effects using continuity equation of density in conservation mass rate law. Plasma species in inter-electrode gap are accelerated by the electric field across the gap and produced high density plasma. Electrons with high energy in arc discharge plasma cause extended ionization, excitation, recombination, and dissociation process due to particle collision which leads to enrichment of density in spatial and temporal mode. The extrapolation of species dominant in arc discharge process is critical issue to predict carbon nanostructure production. A chemical kinetic models and distribution of carbon ions and neutrals species based on collision in thermal plasma condition is developed. The reaction process of carbon species are identified in the between electrodes region. The electron-ion recombination cross section is analyzed to understand the density evolution.
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A reliable Nd:YAG laser welded stainless steel 304 for photonics device packaging application
(2011-05-02)
Nawi, I. N.
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Saktioto
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Fadhali, M.
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Hussain, M. S.
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Ali, J.
An ultra compact pulsed Nd:YAG laser with laser beam peak power of 3.5 kW and 6.5 ms pulse duration is employed to produce a butt joint and lap joint for both spot and seam welding on a stainless steel 304 specimen. The strength test of the weld joints is conducted by pulling the joint materials using INSTRON Series IX/s Automated Materials Tester System. From the experimental results, it is found that a butt joint produces much stronger attachment than a lap joint. The stronger attachment is contributed by a larger volume of welded stainless steel 304 at the joint interfaces. However, the strength of a lap joint can be increased by producing a deeper weld penetration depth. It is done by controlling the laser beam parameters such as laser peak power and pulse duration. It is inferred that the commercial welding material, InvarTM, provides more robust joint than stainless steel 304. It is also concluded that the welded stainless steel 304 cannot attain the strength and elastic modulus of the stainless steel 304 itself. However, the stainless steel 304 is a good welding material for photonics device packaging by using pulsed Nd:YAG laser welding technique.
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Radiation self absorption effect in Ar gas NX2 Mather type plasma focus
(2011-05-02)
Ali, Z.
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Lee, S.
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Ismail, F. D.
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Saktioto
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Ali, J.
The effect of self absorption becomes significant when plasma is dense enough to behave as optically thick. It is essential to account for the effect of self-absorption in that case. The variation of radial trajectory is investigated in this paper. In order to analyze the effect of self absorption of line radiation is investigated in argon plasma by observing the influence of pressure variation of gas. On comparison of the results of numerical experiment considering both aspects i.e. by including and excluding the self absorption term in Lee code an obvious deviation between the trajectories is observed. Last few fractions of seconds (200-300 ns) corroborated the slow compression phase. Results with self absorption showed the compression levels off while without self absorption radiative collapse was observed due to radiative cooling. Due to self absorption the absorbed radiation kept the plasma from radiative collapse turning the results to be more realistic.
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Nd:YAG laser welding of stainless steel 304 for photonics device packaging
(2011-05-02)
Nawi, I. N.
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Saktioto
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Fadhali, M.
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Hussain, M. S.
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Ali, J.
Although pulsed Nd:YAG laser welding has been widely used in microelectronics and photonics packaging industry, a full understanding of various phenomena involved is still a matter of trials and speculations. In this research, an ultra compact pulsed Nd:YAG laser with wavelength of 1.064 μm has been used to produce a spot weld on stainless steel 304. The principal objective of this research is to examine the effects of laser welding parameters such as laser beam peak powers, pulse durations, incident angles, focus point positions and number of shots on the weld dimensions: penetration depth and bead width. The ratio of the penetration depth to the bead width is considered as one of the most critical parameters to determine the weld quality. It is found that the penetration depth and bead width increase when the laser beam peak power, pulse duration and number of shot increase. In contrast, the penetration depth decreases when the laser beam defocus position and incident angle increase. This is due to the reduction of the laser beam intensity causing by the widening of the laser spot size. These experimental results provide a reference on an optimal laser welding operations for a reliable photonics device packaging. The results obtained shows that stainless steel 304 is suitable to be used as a base material for photonics device packaging employing Nd:YAG laser welding technique.
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Graphite thin film deposition using laser induced plasma
(2011-05-02)
Chaudhary, K. T.
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Qindeel, R.
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Saktioto
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Hussain, M. S.
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Ali, J.
The Excimer KrF laser (of wave length 248 nm, pulse energy of 13-50 mJ and pulse width of 20 ns) has been used to ablate graphite solid target. Thin films of graphite material have been grown on silicon (Si) substrate at different temperatures (25°C & 300°C). The techniques x-ray diffraction (XRD) and scanning electron microscopy has been used to study the structure and surface morphology of the deposited thin films. The whole experiment has been performed in the stainless steel chamber under pressure 10-4 torr and each thin film has been deposited for 10,000 laser shots. The graphite thin film deposited at higher substrate temperature has smooth structure and the film is uniform.
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Tunable coupling ratio for optical switch application
(2010-12-01)
Saktioto
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Hanim, Nor Faridah
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Fadhali, M.
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Yupapin, Preecha
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Ali, Jalil
This paper describes the breakdown voltage of SiO<inf>2</inf> fiber using Pockel's effect and empirical equation. The model is evaluated by coupling coefficient and refractive index changes. A 1×2 single-mode directional coupler switch has been fabricated. A large electro-optic effect causes a change in the optical properties when a slowly varying electric field is applied. A model to describe the breakdown voltage for driving the optical switch of the fusion SiO<inf>2</inf> fiber coupler has been developed. A voltage is applied through sectioned electrodes along the coupling length. This model uses the coupling coefficient and the changes in the refractive index to describe the optical switching. The change of refractive index due to the linear electro-optic Pockel effect and an empirical equation are used to calculate the value of coupling coefficient. The result shows that the changes of the refractive index increases exponentially as a function of separation fiber axis from 5 to 8 μm. The breakdown voltage and refractive indices difference depict a linear relationship. The increment of coupling coefficient shows that the value of voltage is reduced. © 2010 SPIE.
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Effect of separation length on dual fibre Bragg gratings
(2010-12-01)
Nafisah, S.
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Saktioto
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Fadhali, M.
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Yupapin, P. P.
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Ali, J.
This paper will investigate the transmission series of dual FBGs when the separation length between two FBGs is varied from 0.5 cm to 5.5 cm. The transfer matrix 2×2 is applied to complete the work. The introduction of separation length affects the transmission spectrum, indicated by the numbers of minimum dip values. Result shows that increasing the separation length between two FBG's lead to the formation of phase shift and increases the number of minimum transmission dip. © 2010 SPIE.
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External disturbance of potential energy photon in fiber Bragg grating
(2010-12-01)
Hairi, Haryana Mohd
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Saktioto
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Fadhali, M.
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Yupapin, P. P.
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Ali, Jalil
The effect of nonlinear parametric known as alpha (α), beta (β) and gamma (γ) has been successfully calculated and a new effect of theta (θ) is introduced to describe the motion of photon in a fiber Bragg grating as a factor of external disturbance. This study is developed under Bragg resonance condition where the initial frequency of the light, ω<inf>0</inf> is the same value as the Bragg frequency, ω<inf>B</inf>. We found that the potential well is not symmetric and conserved. © 2010 SPIE.

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