Liquid Atomization Induced by Pulse Laser Reflection underneath Liquid Surface

Abstract

We observed a novel effect of pulse laser reflection at the interface between transparent materials with different refractive indices. The electric field intensity doubles when a laser beam is completely reflected from a material with a higher refractive index to a material with a lower index. This effect appreciably reduces pulse laser ablation threshold of transparent materials. We performed experiments to observe the entire ablation process for laser incidence on the water–air interface using pulse laser shadowgraphy with high-resolution film; the minimum laser fluence for laser ablation at the water–air interface was approximately 12–16 J/cm2. We confirmed that this laser ablation occurs only when the laser beam is incident on the water–air interface from water. Many slender liquid ligaments extend like a milk crown and seem to be atomized at the tip. Their detailed structures can be resolved only by pulse laser photography using high-resolution film.