Qualification: 
Ph.D, MSc, M.Tech
m_sivakumar@cb.amrita.edu

Dr. Sivakumar M. currently serves as Associate Professor in Physics, Department of Sciences, School of Engineering, Coimbatore. His areas of research include Laser Materials Processing  

Publications

Publication Type: Journal Article

Year of Publication Publication Type Title

2010

Journal Article

Dr. Sivakumar M., Tan, B., and Venkatakrishnan, K., “Enhancement of Silicon Nanostructures Generation Using Dual Wavelength Double Pulse Femtosecond Laser Under Ambient Condition”, Journal of Applied Physics, vol. 107, p. 044307, 2010.[Abstract]


In this study we propose a unique method to increase the weblike silicon nanofibrous structures formation using dual wavelength double pulse femtosecond laser radiation under ambient condition. The augmentation of nanostructures is evidenced from the difference in nanofibrous structure layer thickness. Enhancement in generation is explained through the increase in excited state electrons with double pulse as compared to single pulse. Moreover the absorption characteristic of irradiated surface undergoes significant changes after the first pulse (515 nm) which enhances absorption for the second pulse (1030 nm) and consequently results in an increase in nanostructures. More »»

2009

Journal Article

Dr. Sivakumar M., Oliveira, V., Vilar, R., and Oliveira, S., “Shear Bond Stress of Composite Bonded to Excimer Laser Treated Dentin”, Journal of Laser Applications, vol. 21, pp. 129–132, 2009.[Abstract]


The aim of this work was to study the bond strength of resin composite bonded to dentin surfacestreated with KrF excimer laser radiation, untreated surfaces, and acid-etched surfaces using a single-plane shear method. Dentin specimens cut from freshly extracted permanent molar teeth were subjected to laser treatment with a KrF excimer laser (248 nm) using a fluence of 1 J/cm2. The bond strength was greater for acid-etched specimens than for laser treated or untreated specimens. The low strength of the bond to laser treatedsurfaces is probably due to a shift from a mixed to a cohesive rupture mechanism. It was concluded from this study that surface treatment of dentin surfaces with KrF excimer laser under the conditions described does not significantly improve the shear bond strength to composites. More »»

2006

Journal Article

Dr. Sivakumar M., Oliveira, V., Oliveira, S., Leitão, J., and Vilar, R., “Influence of Tubule Orientation on Cone-Shaped Texture Development in Laser-Ablated Dentin”, Lasers in medical science, vol. 21, pp. 160–164, 2006.[Abstract]


In the present paper, the influence of tubule orientation on surface texture development was studied. Specimens of dentin with a wide range of tubule orientations were extracted from caries-free human teeth, processed using KrF laser radiation, and analyzed by scanning electron microscopy. When a transverse cross section of dentin cut perpendicularly to the tooth axis is processed with KrF laser radiation, a cone-like topography develops in the inner dentin where tubules are parallel to the laser beam. When laser processing is carried out in the outer dentin, because tubules are significantly tilted with respect to the laser beam, flat surfaces are achieved. The surface texture after laser processing depends effectively on the angle between the tubules and the laser beam. The dependency of cone growth on tubule orientation was confirmed using a simple differential ablation model. More »»

Publication Type: Conference Paper

Year of Publication Publication Type Title

2008

Conference Paper

Dr. Sivakumar M., Oliveira, V., Vilar, R., and Rego, A. M. Botelho do, “KrF Excimer Laser Ablation of Human Enamel”, in Materials Science Forum, 2008.[Abstract]


Laser treatment is a promising technique for dental applications such as caries prevention, dental hypersensitivity reduction and improvement of bond strength of restoration materials. In this study the morphological, structural and chemical changes of enamel surface due to treatment with KrF excimer laser radiation were evaluated using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. For radiation fluences near 1 J/cm², laser processing originates a relatively porous surface due to preferential removal of material in the enamel prism sheaths. Increasing the fluence leads to a relatively flat surface with clear evidence of surface melting. The X-ray diffractograms of both treated and untreated enamel are similar and correspond to hydroxyapatite. The only modification due to the laser treatment is a slight shift of the peaks, probably, due to a loss of the structural water of hydroxyapatite. X-ray photoelectron spectroscopy confirmed that organic matter is removed from the irradiated surface but no significant changes in the mineral phase occur. More »»
Faculty Research Interest: 
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