Laser ablation of polymers has been studied with designed materials to evaluate the mechanism of ablation and the role of photochemically active groups on the ablation process, and to test possible applications of laser ablation and designed polymers. The incorporation of photochemically active groups lowers the threshold of ablation and allows high-quality structuring without contamination and modification of the remaining surface. The decomposition of the active chromophore takes place during the excitation pulse of the laser and gaseous products are ejected with supersonic velocity. Time-of-flight mass spectrometry reveals that a metastable species is among the products, suggesting that excited electronic states are involved in the ablation process. Experiments with a reference material, i.e., polyimide, for which a photothermal ablation mechanism has been suggested, exhibited pronounced differences. These results strongly suggest that, in case of designed polymers which contain photochemically active groups, a photochemical part in the ablation mechanism cannot be neglected. Various potential applications for laser ablation and the special photopolymers were evaluated and it became clear that the potential of laser ablation and specially designed material is in the field of microstructuring. Laser ablation can be used to fabricate three-dimensional elements, e.g., microoptical elements.

Laser application of polymers

This paper provides a review of papers published on laser interaction with solids, from the point of view of plasma production. The material is divided into one section dealing with theoretical work and one dealing with experiments. In addition, an extensive bibliography of papers published on the subject up to the end of 1968 is presented.

Laser interaction with solids - A bibliographical review

Laser-induced breakdown spectroscopy (LIBS) has been developed since the invention of the laser in 1960. The push from analytical companies from the beginning started a huge scientific adventure combining analytical science, plasma physics engineering and commercialization that still is in place fifty years later. This historical review of the first five years of laser‐based micro‐spectrochemical analysis introduces the first measurements and systems for laser micro-analysis and its evolution to conventional LIBS.

The first years of laser-induced breakdown spectroscopy

Electronic, vibrational and rotational temperatures in laser-produced flames measured spectroscopically

Spectroscopic Temperature Measurements on Laser‐Produced Flames

The study of the interaction of high-power lasers with solid matter is as old as the laser itself. Variously termed laser ablation, vaporization, sputtering, desorption, spallation or etching, the physical processes involved are extremely complex. Electromagnetic energy is converted to electronic, thermal, chemical and mechanical energy at the solid surface. The ejected material may include neutral atoms and molecules, positive and negative ions, clusters, electrons and photons. The generated plasmas may have electron temperatures of thousands of degrees. Of necessity a multidisciplinary problem, the mechanism of laser ablation is still being studied and debated.

History, Scope, and the Future of Laser Ablation

WHEN a high-power laser beam is focused on to a material target, a small inertially confined plasma is generated near the target surface. Theoretical work by Basov and Krokhin1,2, verified by Dawson3, suggests that very hot plasmas (∼107 °K) can ultimately be produced in this way. A spectroscopic investigation of plasmas generated by a small Q-switched ruby laser has already been reported4. Further experiments have now been carried out using a larger Q-switched neodymium glass laser, and an estimate of the electron temperature attained in a carbon plasma is reported in this communication. Other results will be described in detail elsewhere.

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T.P. Hughes

Papers

Electron temperature in a laser-heated plasma