Session H6: Applications of Free Electron Lasers I

Materials Processing with FEL Radiation- An Overview

A unique feature of FEL's is their enormously wide range of output parameters, enabling ``processing by design''., The FEL's energy delivery can be matched to materials properties, accomplishing the intended transformation. The immediate beneficiary is materials R{\&}D, where systematic experimental investigations can now truly dance with computational modeling to make unique materials. For example, depositing energy into specific organic molecular bonds in a time frame too brief for escape into the rest of the molecule, results in selective bond scission. Collecting the ablated fragments on a substrate affords a molecularly faithful coating. Solvent-related complications of conventional coating are avoided, a greater advantage the wider the range of organics to be explored. Sharply adapting the FEL's design to a specific parameter set and taking advantage of the fall of unit cost with increasing power holds promise for applications in manufacturing. Several potential applications in ablative materials synthesis, rapid thermal processing and surface photochemistry will be briefly discussed.   

Infrared Pulsed Laser Deposition: Applications in Photonics and Biomedical Technologies

Resonant infrared pulsed-laser deposition (RIR-PLD) shows significant promise for synthesizing thin films of small organic molecules, thermoplastic and thermosetting polymers and biopolymers, without compromising structure or functionality. This contrasts with most attempts at UV-PLD of organic materials, which have often been accompanied by severe photochemical or photothermal degradation of the ablated material. Representative recent successes in RIR-PLD include deposition of: polymers for light emission and hole transport; functionalized polymers and nanoparticles for chemical and biological sensing; and biocompatible polymers suitable for coating medical devices or drug-delivery vehicles. Plume imaging and various other optical- and mass-spectroscopy experiments appear to confirm that polymers or organic molecules ablated by resonant infrared laser irradiation experience a high spatial and temporal density of vibrational excitation, but tend to remain in the electronic ground state. The mechanism of RIR-PLD is observed to depend on the anharmonicity of the mid-infrared absorption modes, their finite relaxation time, mode-specific nonlinear absorption, and rapid changes in polymer viscosity as a function of temperature. Many of the RIR-PLD experiments to date were carried out using a tunable, mid-infrared, picosecond free-electron laser. However, if RIR-PLD is to become a practical tool for making organic thin films, it will be necessary to develop more conventional lasers that can achieve a similar combination of high pulse intensity, low pulse energy, high pulse-repetition frequency and moderate average power. In conclusion, the prospects for developing precisely such table-top RIR-PLD systems will be discussed.