Laser Material Processing for Microengineering Applications

The processing of materials via laser irradiation is presented in a brief survey. Various techniques currently used in laser processing are outlined and the significance to the development of space qualified microinstrumentation are identified. In general the laser processing technique permits the transferring of patterns (i.e. lithography), machining (i.e. with nanometer precision), material deposition (e.g., metals, dielectrics), the removal of contaminants/debris/passivation layers and the ability to provide process control through spectroscopy

A High-Average-Power Free Electron Laser for Microfabrication and Surface Applications

CEBAF has developed a comprehensive conceptual design of an industrial user facility based on a kilowatt ultraviolet (UV) (160-1000 mm) and infrared (IR) (2-25 micron) free electron laser (FEL) driven by a recirculating, energy recovering 200 MeV superconducting radio frequency (SRF) accelerator. FEL users, CEBAF's partners in the Lase Processing Consortium, including AT&T, DuPont, IBM, Northrop Grumman, 3M, and Xerox, are developing applications such as metal, ceramic, and electronic material micro-fabrication and polymer and metal surface processing, with the overall effort leading to later scale-up to industrial systems at 50-100 kW. Representative applications are described. The proposed high-average-power FEL overcomes limitations of conventional laser sources in available power, cost-effectiveness, tunability, and pulse structure

UV Tunable Laser Ablation of YBa₂Cu₃O_x+6: Changes in the Product Population and Kinetic Energy Distributions as a Function of the Laser Wavelength and Target Bulk Temperature

ABSTRACTWe have conducted two separate experiments in the UV laser ablation of a sintered Yba2Cu3Ox+6wafer. We have measured the photoejected population distributions using selected UV laser wavelengths (4.01, 4.17 and 4.35 eV) near the 4.1 eV optical transition in Yba2Cu3Ox+6 In addition, we have measured the change in the ejected species kinetic energy as a function of the target bulk temperature. All the experiments were conducted at laser fluences well below the plasma formation threshold, and near that for product formation. Our results show that the UV laser ablation, at threshold fluences, proceeds via a nonthermal electronic excitation mechanism.</jats:p

Threshold Level Laser Ablation of Yba₂Cu₃O_x+6 at 351 nm, 248 nm, and 193 nm: Ejected Product Population and Kinetic Energy Distributions

ABSTRACTUsing a sintered Yba2Cu3Ox+6 wafer in high vacuum, we have measured the photo-ejected products and kinetic energies at selected UV laser wavelengths (351 nm, 248 nm, and 193 nm) where the laser fluence is maintained near product formation threshold. At these fluences, we are well below the above surface plasma formation threshold and do not detect; any evidence for surface melting. Our results show that, for a specific laser wavelength, both the ion and the neutral mass spectrum agree. The measured spectrum shows that the photablated products consist only of atomic and diatomic species. In addition, the oxygen is bound only to the yttrium and barium. Our measurements further show that, for a specific ejected species, the yield is dependent on both the laser fluence and wavelength. However, the measured KE distribution is independent of the laser fluence for fluences near threshold. The species are ejected with mean KE between 6–9 eV and no species has kinetic energy in excess of 13 eV Our results imply that for UV laser threshold fluence ablation, the excitation/desorption process is nonthermal.</jats:p