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Pushing a physics discovery towards commercial impact, at REU Seminar, Harvard University (Cambridge, MA), Wednesday, July 24, 2013:
talk_2178.pdf
In 1997 my research group discovered that 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, making this 'black silicon' useful for a wide range of commercial devices, from highly-sensitive detectors to improved photovoltaics. Over the following ten years we investigated this material and developed a prototype detector. The prototype gave us the confidence to commercialize black silicon. Together... Read more about Pushing a physics discovery towards commercial impact
Nonlinear optics at the nanoscale, at European Laboratory for Non-Linear Spectroscopy Seminar, Universitá di Firenze (Florence, Italy), Thursday, July 18, 2013:
talk_2182.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
Novel Nanostructures for Optics and Photonics, at NATO-ASI Summer school on Nano-structures for optics and photonics, Centro Ettore Majorana (Erice, Italy), Friday, July 5, 2013:
talk_1812.pdf
We explore linear 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... Read more about Novel Nanostructures for Optics and Photonics
Nonlinear optics at the nanoscale, at University of Virginia (Charlottesville, VA), Friday, April 12, 2013:
talk_2064.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
Black silicon and the quest for intermediate band semiconductors, at iCone Seminar, University of North Carolina Charlotte (Charlotte, NC), Friday, February 15, 2013:
talk_2065.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.
Black silicon, at 2013 Swenton-Ouellette Lecture, Ohio State University (Columbus, OH), Thursday, February 14, 2013:
talk_2059.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.
The photovoltaic potential of femtosecond laser textured amorphous silicon, at Photonics West (San Francisco, CA), Thursday, February 7, 2013:
talk_2078.pdf
Femtosecond laser texturing of silicon yields nanometer scale surface roughness that reduces reflection and enhances light absorption. In this work, we study the potential of using this technique to improve efficiencies of amorphous silicon-based solar cells by laser texturing thin amorphous silicon films. We use Ti:Sapphire femtosecond laser systems to texture amorphous silicon in either hydrogen or sulfur hexafluoride ambient gases and we also study the effect of laser texturing the substrate before depositing amorphous silicon. We adjust the thin-film thickness and laser fabrication... Read more about The photovoltaic potential of femtosecond laser textured amorphous silicon
Maximizing intensity in TiO2 waveguides for nonlinear optics, at Photonics West (San Francisco, California), Wednesday, February 6, 2013:
talk_2096.pdf
Titanium dioxide (TiO2) represents an attractive candidate for nonlinear optical devices due its high transparency, large refractive index, and large Kerr nonlinearity. Using electron beam lithography and a liftoff procedure, we can structure both amorphous TiO2 as well as polycrystalline anatase thin films to create photonic devices that exploit the material’s properties in order to do nonlinear optics. Nonlinear optics benefit from long interactions, necessitating large intensities along long waveguide lengths. For this reason, waveguide losses need to be minimized. We study the effects... Read more about Maximizing intensity in TiO2 waveguides for nonlinear optics

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