Publications

Burns, George B.; Palmer, Jeremy A.; Harris, Marc F.; McDaniel, Karen L.; Guo, Junpeng; Vawter, Gregory A.; Tallant, David T.; Griffith, M.L.; Luk, Ting S.

At Sandia National Laboratories, miniaturization dominates future hardware designs, and technologies that address the manufacture of micro-scale to nano-scale features are in demand. Currently, Sandia is developing technologies such as photolithography/etching (e.g. silicon MEMS), LIGA, micro-electro-discharge machining (micro-EDM), and focused ion beam (FIB) machining to fulfill some of the component design requirements. Some processes are more encompassing than others, but each process has its niche, where all performance characteristics cannot be met by one technology. For example, micro-EDM creates highly accurate micro-scale features but the choice of materials is limited to conductive materials. With silicon-based MEMS technology, highly accurate nano-scale integrated devices are fabricated but the mechanical performance may not meet the requirements. Femtosecond laser processing has the potential to fulfill a broad range of design demands, both in terms of feature resolution and material choices, thereby improving fabrication of micro-components. One of the unique features of femtosecond lasers is the ability to ablate nearly all materials with little heat transfer, and therefore melting or damage, to the surrounding material, resulting in highly accurate micro-scale features. Another unique aspect to femtosecond radiation is the ability to create localized structural changes thought nonlinear absorption processes. By scanning the focal point within transparent material, we can create three-dimensional waveguides for biological sensors and optical components. In this report, we utilized the special characteristics of femtosecond laser processing for microfabrication. Special emphasis was placed on the laser-material interactions to gain a science-based understanding of the process and to determine the process parameter space for laser processing of metals and glasses. Two areas were investigated, including laser ablation of ferrous alloys and direct-write optical waveguides and integrated optics in bulk glass. The effects of laser and environmental parameters on such aspects as removal rate, feature size, feature definition, and ablation angle during the ablation process of metals were studied. In addition, the manufacturing requirements for component fabrication including precision and reproducibility were investigated. The effect of laser processing conditions on the optical properties of direct-written waveguides and an unusual laser-induced birefringence in an optically isotropic glass are reported. Several integrated optical devices, including a Y coupler, directional coupler, and Mach-Zehnder interferometer, were made to demonstrate the simplicity and flexibility of this technique in comparison to the conventional waveguide fabrication processes.

Journal of Applied Physics

Yang, Pin Y.; Burns, George B.; Guo, Junpeng; Luk, Ting S.; Vawter, Gregory A.

The optical birefringence in an isotropic glass medium was created by using a regeneratively amplified Ti:sapphire femtosecond laser. The regions between two crossed polarizers modified by the femtosecond laser shows bright transmission with respect to the dark background of the isotropic glass. It was found that the angular dependence of transmission through the laser-modified region was consistent with that of an optically birefringent material. It was also observed that the optical axes of laser-induced birefringence can be controlled by the polarization direction of the femtosecond laser.

Vawter, Gregory A.; Peters, D.W.; Wendt, J.R.; Hadley, G.R.; Vawter, Gregory A.; Peake, Gregory M.; Guo, Junpeng; Subramania, Ganapathi S.

Artificially structured photonic lattice materials are commonly investigated for their unique ability to block and guide light. However, an exciting aspect of photonic lattices which has received relatively little attention is the extremely high refractive index dispersion within the range of frequencies capable of propagating within the photonic lattice material. In fact, it has been proposed that a negative refractive index may be realized with the correct photonic lattice configuration. This report summarizes our investigation, both numerically and experimentally, into the design and performance of such photonic lattice materials intended to optimize the dispersion of refractive index in order to realize new classes of photonic devices.

Proposed for publication in Applied Physics Letters.

Yang, Pin Y.; Yang, Pin Y.; Burns, George B.; Guo, Junpeng; Luk, Ting S.; Vawter, Gregory A.

Abstract not provided.