Excimer Laser Ablation Of Polymers Research Articles

Underwater excimer laser ablation of polymers

In this paper, we study the photoablation kinetic of poly (ethylene terephthalate) (PET), polycarbonate (PC), polyimide (PI) and polystyrene (PS) in both air and water. Compared to the results obtained in air, we highlight the decrease of the ablation threshold (AT) of polyesters in contact with water as a function of polymer chemical structure. In order to check the expected hydrolytic reaction of polyesters near the ablation threshold, the chemical modification of the polymer surfaces, as well the composition of the ablation products, were investigated after irradiation near the fluence of ablation threshold in air (air-Ft) by X-ray photoelectron spectroscopy (XPS) and confocal Raman microspectroscopy. The morphology of polymers obtained by underwater irradiation and near the air-Ft was also examined using scanning electron microscopy (SEM). To understand the process and its dynamics in contact with water, we consider the model of temperature at the polymer-water interface based on the semi-analytical solution of the transit heat-diffusion equation.

Excimer laser ablation of polymers and glasses for grating fabrication

In this paper we describe studies carried out related to grating formation for optoelectronics applications using 248 nm and 193 nm excimer lasers. These include basic studies of UV laser induced incubation and ablation of various glasses, and an evaluation of laser-induced-periodic-surface-structures (LIPSS) and UV holographic techniques based on a phase mask for forming gratings on polymers and in fibres. Modelling and experiments show that the use of excimer laser illuminated phase masks in a contact printing mode or Talbot reimaging arrangement provide a particularly effective approach to forming submicron period gratings.

Diamond films by the excimer laser photoablation of polymers

The chemical vapor deposition of diamond films on silicon and various other substrates from a methane/hydrogen mixture, as well as from other gas compositions, uses plasma, a hot filament, or an acetylene torch to generate the reactive species. Although the attempt to produce diamond films from polymers is not new, crystalline diamond structures have yet to be obtained; only diamond-like carbon has been reported. The technique described here features the excimer laser ablation of polymers and the formation of crystalline diamond. A Raman peak at 1,330 cm−1 clearly identifies diamond, but its shape also reveals the presence of graphite. Peaks at 1,350 −1 and 1,597 cm−1 identify glassy carbon. Scanning electron microscopy micrographs reveal the crystalline structure. Cubic blocks are formed, as well as grains of about 1 μ size showing facets of all kinds reported for diamonds.

Dynamics of laser-induced periodic surface structures in excimer laser ablation of polymers

In situ microscopy and optical diffraction studies of ripple structures produced on excimer laser ablated polymers are reported, allowing their development rate to be estimated and motion to be observed. The formation of these ‘‘anomalous’’ ripple structures (grating vector perpendicular to the polarized laser electric field direction) is analyzed within the framework of a model describing interference between the transmitted and diffracted beams at the surface. Experimental observations are consistent with theory if substantial modification of the (effective) optical constants of the polymer occurs under ablation conditions. A model describing the ripple dynamics under multipulse irradiation is reported and compared with the experimental findings.

Schlieren measurements of the hydrodynamics of excimer laser ablation of polymers in atmospheric pressure gas

Pulsed schlieren photography and fast helium-neon laser deflection are used to study the hydrodynamics of laser ablation of polyethyleneterephthalate and polymethylmethacrylate by pulsed KrF (248 nm) radiation in atmospheric air, Ar and N2. Schlieren measurements show the evolution of shock waves, sound waves, and reduced-density, hot gas plumes. A transition from sound to shock at the ablation threshold for both polymers is observed. The shock velocity of PET tends to approach agreement with blast wave theory at fluences higher than 1 J/cm2. Plumes in air are consistently larger than those produced in Ar and N2 (at fluences below 5 J/cm2) suggesting that combustion may occur. Laser deflection measurements for PET at 150 mJ/cm2 indicate a plume density of 0.6 kg/m3 (50% atmospheric density).

Excimer laser ablation of polymers and carbon fiber composites.

Excimer laser ablation of polymers and carbon fiber composites.

Laser beam deflection as a probe of laser ablation of materials

Helium-neon laser beam deflection is used to study excimer laser ablation of polymers and a YBa2 Cu3 O7−x superconductor. Density gradients above pulsed laser heated or ablated samples deflect the He-Ne laser beam and this is measured using a position sensitive detector. The technique permits the determination of the laser fluence threshold for ablation both in a vacuum and in air, and the velocity of the ablation products in a vacuum. A model of the thermal deflection at low fluence was developed which enables measurements of thermal diffusivity of the air.