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Submicrosecond Dynamics Of Water Explosive Boiling And Lift-Off From Laser-Heated Silicon Surfaces, S. I. Kudryashov, S. D. Allen

Mechanical Engineering - Daytona Beach

Explosive boiling and lift-off of a thin layer of micron-sized transparent water droplets from an absorbing Si substrate heated by a nanosecond KrF laser were studied using a contact photoacoustic technique. The compressive photoacoustic response increases steeply to an asymptotic value on the order of the water critical pressure starting at a threshold laser fluence of 0.20 J cm2, where lift-off of the water layer also occurs. Above this threshold, several reproducible discrete multimegahertz components are revealed in Fourier spectra of the acoustic transients, corresponding to nanosecond oscillations of steam bubbles inside the water droplets on the microsecond time scale …

Laser Ablation Of Optically Thin Absorbing Liquid Layer Predeposited Onto A Transparent Solid Substrate, S. I. Kudryashov, K. Lyon, S. D. Shukla, D. Murry, S. D. Allen

Mechanical Engineering - Daytona Beach

Ablation of optically thin liquid 2-propanol layers of variable thickness on IR-transparent solid Si substrate by a nanosecond CO ₂laser has been experimentally studied using time-resolved optical interferometric and microscopy techniques. Basic ablation parameters - threshold fluences for surface vaporization and explosive homogeneous boiling of the superheated liquid, ablation depths, vaporization (ablation) rates, and characteristic ablation times versus laser fluence - were measured as a function of alcohol layer thickness. The underlying ablation mechanisms, their thermodynamics, and microscopic details are discussed.

c 2006 American Institute of Physics