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Black silicon and the quest for intermediate band semiconductors, at Siam Physics Congress 2015 (Krabi, Thailand), Thursday, May 21, 2015:
talk_2462.pdf
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
Direct Laser Writing of 3D Gratings and Diffraction Optics, at CLEO: Science and Innovations Laser-Induced Structuring in Bulk Material (SW1K) (San Jose, CA), Wednesday, May 13, 2015:
talk_2486.pdf
We fabricate 3D gratings and diffraction optics using direct laser writing. Diffraction patterns of gratings agree with Laue theory. We demonstrate zone plates for visible wavelengths. Direct laser writing is promising for integrated diffraction optics.
Making light go infinitely fast, at RCC Workshop on Nanomaterials, Real Colegio Complutense at Harvard University (Cambridge, MA), Friday, May 1, 2015:
talk_2477.pdf
Impedance-matched metamaterials with zero refractive index can be achieved by exploiting a Dirac cone at the center of the Brillouin zone. We present an in-plane Dirac-cone metamaterial consisting of low-aspect-ratio silicon pillar arrays in an SU-8 matrix with top and bottom gold layers. Using an integrated nano-scale prism constructed of the proposed material, we demonstrate unambiguously a zero refractive index in the optical regime. This design serves as a novel on-chip platform in the optical regime to explore the exotic physics of Dirac-cone metamaterials and to implement applications... Read more about Making light go infinitely fast
Nonlinear optics at the nanoscale, at Condensed Matter Colloquium, University of Utah (Salt Lake City, UT), Tuesday, March 3, 2015:
talk_2424.pdf
We explore nonlinear optical phenomena at the nanoscale by launching femtosecond laser pulses into long silica nanowires. Using evanescent coupling between wires we demonstrate a number of nanophotonic devices. At high intensity the nanowires produce a strong supercontinuum over short interaction lengths (less than 20 mm) and at a very low energy threshold (about 1 nJ), making them ideal sources of coherent white-light for nanophotonic applications. The spectral broadening reveals an optimal fiber diameter to enhance nonlinear effects with minimal dispersion. We also present a device that... Read more about Nonlinear optics at the nanoscale
Nonlinear optics at the nanoscale, at University of Florida (Gainesville, FL), Monday, February 16, 2015:
talk_2398.pdf
We explore nonlinear optical phenomena at the nanoscale by launching femtosecond laser pulses into long silica nanowires. Using evanescent coupling between wires we demonstrate a number of nanophotonic devices. At high intensity the nanowires produce a strong supercontinuum over short interaction lengths (less than 20 mm) and at a very low energy threshold (about 1 nJ), making them ideal sources of coherent white-light for nanophotonic applications. The spectral broadening reveals an optimal fiber diameter to enhance nonlinear effects with minimal dispersion. We also present a device that... Read more about Nonlinear optics at the nanoscale
Plasmonic Cell Transfection using Micropyramid Arrays, at SPIE Photonics West, SPIE (San Francisco, CA), Sunday, February 8, 2015:
talk_2422.pdf
We present a new cell transfection method that uses femtosecond laser-excited localized surface plasmons (LSPs) on a nanostructured micropyramid array. Our gold-layered micropyramids have nano-apertures at the apex to form high local electric field enhancements, or “hot spots.” These hot spots form microbubbles that temporarily perforate mammalian cell (HeLa S3) membranes and allow dye molecules and plasmid vectors to diffuse through the membrane openings. We introduce an emerald green fluorescent protein (EmGFP) reporter plasmid into the cells to determine the LSP-mediated transfection... Read more about Plasmonic Cell Transfection using Micropyramid Arrays
High Throughput Poration of Mammalian Cells using Femtosecond Laser-activated Plasmonic Substrates, at Tokyo Metropolitan University (Tokyo, Japan), Thursday, January 29, 2015:
talk_2425.pdf
We present a new cell transfection method that uses femtosecond laser-excited localized surface plasmons (LSPs) on a nanostructured micropyramid array. Our gold-layered micropyramids have nano-apertures at the apex to form high local electric field enhancements, or “hot spots.” These hot spots form microbubbles that temporarily perforate mammalian cell (HeLa S3) membranes and allow dye molecules and plasmid vectors to diffuse through the membrane openings. We optimize our laser parameters for successful poration and high cell viability. Our nontoxic, efficient, and scalable technique... Read more about High Throughput Poration of Mammalian Cells using Femtosecond Laser-activated Plasmonic Substrates
Femtosecond Materials Processing I: Transparent and soft materials, at Tsing Hua Univeristy (Beijing, China), Wednesday, December 17, 2014:
talk_2385.pdf
The intersection of materials research and ultrafast optical science is producing many valuable fundamental scientific results and applications, and the trend is expected to evolve as new and exciting discoveries are made. Femtosecond laser micromachining presents unique capabilities for three-dimensional, material-independent, sub-wavelength processing. At the same time the surface processing of materials permits the creation of novel materials that cannot (yet) be created under other conditions. In the first part of this talk we will discuss how when the ultashort laser pulses are focused... Read more about Femtosecond Materials Processing I: Transparent and soft materials

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