Laser ablation of a thin carbon layer deposited on a polymer substrate by Nd:YAG laser

A thin carbon film of 200 nm thickness was deposited on a polymethyl methacrylate (PMMA) substrate. It was then used as a target for laser ablation. The laser beam was focused from the rear through a PMMA. We call this special target ''thin film target'', which is found to enhance the laser energy density absorbed by the target. Infrared wavelength of Nd:YAG laser is used in this study due to the efficient absorption of energy by the ablated plasma plume. Ablation emission was observed by the high-speed streak camera, and it was shown to emanate from both sides of the target. The plume is seen to be composed of several groups moving with different velocities. The high velocity component in the rear side disappears with decreasing fluence intensity, i.e., the plume density increases with laser fluence, whose value is above the ablation threshold of PMMA