Sivarama Krishnan

In micromachining, the extruded material is re-deposited back on the structured surface. In this work, we report on the advantages and results of fs laser-based surface micromachining of methanol immersed of Si comparing the same with the ambient air.

In micromachining, the extruded material is redeposited back on the structured surface. In this work, we report on the advantages and results of fs laser-based surface micromachining of methanol immersed of Si comparing the same with the ambient air.

Femtosecond laser-assisted surface texturing of compression piston rings is proposed and demonstrated. A femtosecond pulsed Ti3+:sapphire laser is used to generate dimples of the same size but with different area density on a moly-chrome ceramic deposited cast iron piston ring. The influence of the surface morphology and tribology operating conditions, such as reciprocating frequency and temperature of the lubricant, on friction and wear characteristics of textured piston rings and plateau honed liner samples is investigated. A decrease in the friction coefficient is observed with the texturing of rings. The dimple area density, which is defined as the ratio of the total textured area and the total area of the surface, of 16% and 27% offered a reduced coefficient of friction and minimize wear on the liner surface.

We explore transient grating formation in CS2 with femtosecond pulses. The spatially periodic excitation changes the nonlinear refractive index of the medium periodically, resulting in diffraction of the probe beam. The pump power dependence of the self-diffraction efficiency shows a second order power-law indicating the process involving a third-order nonlinearity. Time-resolved diffraction of the probe beam measured with a photodiode gives the third-order autocorrelated signal. CS2 having large third order nonlinearity in a broad range of wavelengths in the visible and near-infrared, is proposed to be a promising candidate for measuring the pulse-widths for pulses generated from optical parametric amplifiers (OPA) using this technique.