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Femtosecond Materials Processing II: Nontransparent materials, at Tsing Hua Univeristy (Beijing, China), Wednesday, December 17, 2014:
talk_2386.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 II: Nontransparent materials
Direct Laser Writing of 3-D Diffraction Gratings and Diffraction Optics, at MRS 2014 Fall Meeting and Exhibit, Symposium L: Optical Metamaterials and Novel Optical Phenomena Based on Nanofabricated Structures (Boston, MA), Thursday, December 4, 2014
Integrated diffractive optics has many applications in beam shaping and control on the micro-scale. Fabrication using lithography is limited to planar or layered geometries. We demonstrate fabrication of diffractive elements via direct laser writing. We have tested 3D diffraction gratings and zone plates designed for operation at visible wavelengths. Direct laser writing is a promising technique to fabricate integrated 3D and multi-layer diffraction optics. We have previously developed a laser writing technique that enables fabrication of disconnected metal structures in a polymer matrix,... Read more about Direct Laser Writing of 3-D Diffraction Gratings and Diffraction Optics
Black silicon, at Physics Colloquium, Auburn University (Auburn, AL), Friday, September 19, 2014:
talk_2354.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.
Pushing a physics discovery towards commercial impact, at REU Seminar, Harvard University (Cambridge, MA), Wednesday, July 16, 2014:
talk_2352.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
Femtosecond laser micromachining, at Extreme photonics Summer School: Ultrafast Lasers and Applications, University of Ottawa (Ottawa, ON, Canada), Thursday, June 26, 2014:
talk_2349.pdf
When femtosecond laser pulses are focused tightly into a transparent material, the intensity in the focal volume can become high enough to cause nonlinear absorption of laser energy. The absorption, in turn, can lead to permanent structural or chemical changes. Such changes can be used for micromachining bulk transparent materials. Applications include data storage and the writing of waveguides and waveguide splitters in bulk glass, fabrication of micromechanical devices in polymers, and subcellular photodisruption inside single cells.
Femtosecond-Laser Hyperdoping and Texturing of Silicon for Advanced Non-equilibrium Materials, at 2014 AFOSR Ultrashort Pulse Laser-Matter Interactions Program Review (Arlington, VA), Friday, May 30, 2014:
talk_2331.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 process has two effects: it structures the surface and incorporate dopants into the sample to a concentration highly exceeding the equilibrium solubility limit. This femtosecond laser "hyperdoping technique" enables the fabrication of defect- and bandgap engineered semiconductors, and laser texturing further enhances the optical density through excellent light trapping. Hyperdoped silicon opens the door for novel... Read more about Femtosecond-Laser Hyperdoping and Texturing of Silicon for Advanced Non-equilibrium Materials
Subcellular surgery and nanosurgery, at Western Washington University (Bellingham, WA), Tuesday, May 13, 2014:
talk_2323.pdf
We use femtosecond laser pulses to manipulate sub-cellular structures inside live and fixed cells. Using only a few nanojoules of laser pulse energy, we are able to selectively disrupt individual mitochondria in live bovine capillary epithelial cells, and cleave single actin fibers in the cell cytoskeleton network of fixed human fibro-blast cells. We have also used the technique to micromanipulate the neural network of C. Elegans, a small nematode. Our laser scalpel can snip individual axons without causing any damage to surrounding tissue, allowing us to study the function of individual... Read more about Subcellular surgery and nanosurgery
Nonlinear optics at the nanoscale, at Louisiana State University (Baton Rouge, LA), Monday, April 28, 2014:
talk_2312.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

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