Product Code: PIC2008_M102

Processing of Polymer and Organic Materials using Tunable Ultrafast Mid-Infrared Lasers (Invited Paper)
Authors:
Richard Haglund, Vanderbilt University; Nashville TN USA
Nicole Dygert, Vanderbilt University ; Nashville TN USA
Stephen Johnson, Vanderbilt University ; Nashville TN USA
Kenneth Schriver, Vanderbilt University ; Nashville TN USA
Hee Park, Appliflex Llc; Mountain View CA USA
Presented at PICALO 2008

The principal vibrational modes of many polymers and organic materials of interest for electronic and electro-optic applications lie in the mid-infrared region of the spectrum between 2 and 10 µm. Most of these bands are shown in Figure 7; other potentially interesting bands, such as the CF2 stretching vibrations of the fluoropolymers in the 8 µm region, can be inferred by simple extrapolation of mass ratios. We have recently demonstrated the possibility for efficient gas-phase transfer of intact small organic molecules, polymers, biopolymers and nanoparticles to thin-film substrates by resonant infrared laser ablation in this wavelength range. This has, in turn, opened up new possibilities for applications of this novel pulsed-laser deposition technique. One recent example is the fabrication of light-emitting diodes entirely in vacuum, without any liquid-phase processing; another is the successful deposition of crystalline films of poly(tetrafluoroethylene), the insoluble polymer known better by its trade name, Teflon®. The laser used in almost all of these experiments is a tunable, mid-infrared free-electron laser with a unique macropulse-micropulse. The fact that this laser ablation process can be gentle enough to volatilize these large, thermally labile species appears from experimental evidence to result from two characteristics of this laser: (1) the low energy of the mid-infrared photons employed; and (2) the high spatiotemporal density of excitation produced by the picosecond micropulses. Examples from recent studies of both the physics and applications of this ablation mechanism will be presented. The free-electron laser is a device of almost matchless versatility, that correspondingly comes at the cost of significant complexity. Nevertheless, it is becoming clear that its principal characteristics ultrashort pulse duration, high pulse-repetition frequency and high average power, delivered in a macropulse-micropulse structure are going to become available in the near future in solid-state laser systems. The paper will conclude with a brief review of the state of the art in high-power, picosecond tunable laser systems for mid-infrared applications.