Presentations

    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
    Femtosecond Materials Processing I: Transparent and soft materials, at Tsing Hua Univeristy (Beijing, China), Wednesday, December 17, 2014:
    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
    Femtosecond Materials Processing II: Nontransparent materials, at Tsing Hua Univeristy (Beijing, China), Wednesday, December 17, 2014:
    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
    Laser induced microexplosions in transparent materials, at CLEO/QELS '97 (Baltimore, MD), Friday, May 23, 1997
    We recently discovered that 200-nm diameter structures can be created inside transparent materials by ultrafast-laser driven microexplosions. Applications include high-density 3-D data storage, fabrication of 3-D optical elements, and novel materials processing. We present the results of optical and structural examinations and discuss the physical processes involved.
    3-D Optical data storage in transparent materials, at International Symposium on Optical Memory and Optical Data Storage (Maui, HI), Sunday, June 1, 1997
    We present a novel method for 3-D optical data storage and internal engraving that has submicron-size resolution, provides a large contrast in index of refraction, and is applicable to a wide range of transparent materials.
    Ultrafast laser induced microexplosions: explosive dynamics and sub-micrometer structures, at Photonics West 1998 (San Jose, CA), Monday, January 26, 1998
    Tightly focused femtosecond laser pulses can be nonlinearly absorbed inside transparent materials, creating a highly excited electron – ion plasma. These conditions exist only in a small volume at the laser focus. This tight confinement and extreme conditions lead to an explosive expansion — a microexplosion. In solid materials, a microexplosion can result in permanent structural changes. We find that the damage produced by femtosecond pulses in this way is surprisingly small, with only a 200-nm diameter. Material left at the center of the microexplosion is either amorphous and less dense or... Read more about Ultrafast laser induced microexplosions: explosive dynamics and sub-micrometer structures
    Thresholds for femtosecond laser-induced breakdown in bulk transparent solids and water, at SPIE Annual Meeting, 1998 (San Diego, CA), Wednesday, July 15, 1998
    We present thresholds for optical breakdown in bulk transparent solids and water with 100-fs laser pulses. In solids, we used microscopy and scattering techniques to determine thresholds for plasma formation and permanent damage in a wide variety of materials. Transmission measurements show that damage occurs at energies where there is little absorption of the laser pulse. In water, we used scattering and acoustic techniques to measure the breakdown threshold for 100-fs pulses. In contrast to solids, transmission measurements in water indicate that there is no plasma or bubble formation... Read more about Thresholds for femtosecond laser-induced breakdown in bulk transparent solids and water
    Laser-induced microexplosions in transparent materials: microstructuring with nanojoules, at Photonics West 1999 (San Jose, CA), Tuesday, January 26, 1999
    We tightly focus femtosecond laser pulses in the bulk of a transparent material. The high intensity at the focus causes nonlinear absorption of the laser energy, producing a microscopic plasma and damaging the material. The tight external focusing allows high intensity to be achieved with low energy, minimizing the effects of self-focusing. We report the thresholds for breakdown and critical self-focusing in fused silica using 110-fs pulses at both 400-nm and 800-nm wavelength. We find that permanent damage can be produced with only 10 nJ (25 nJ) for 400-nm (800-nm) pulses, and that the... Read more about Laser-induced microexplosions in transparent materials: microstructuring with nanojoules
    Microstructuring of bulk transparent solids using nanojoule, femtosecond laser pulses, at APS Centennial Meeting 1999 (Atlanta, GA), Tuesday, March 23, 1999:
    We produce sub-micron sized permanent damage in the bulk of dielectric materials using 110-fs laser pulses with only 40 nJ of energy. Tight external focusing (0.65 NA) of the ultrashort laser pulses enables us to achieve a high intensity at the focus with low laser energy. The high intensity leads to nonlinear absorption of the laser pulse by the material, resulting in permanent damage. Achieving high intensity with low energy reduces the effects of self-focusing, and eliminates the need for an amplified laser system. We report thresholds for damage and critical self-focusing in fused silica... Read more about Microstructuring of bulk transparent solids using nanojoule, femtosecond laser pulses
    Femtosecond laser micromachining of bulk glass at oscillator energies, at Gordon Conference on Nonlinear Optics, Colby Sawyer College (New London, NH), Tuesday, July 27, 1999:
    Using femtosecond laser pulses generated by a 25-MHz Ti:Sapphire laser oscillator, we micromachine bulk glass. The laser is focused by a 1.4 numerical aperture microscope objective, allowing the breakdown threshold to be reached with modest energies (4.5 nJ). Single-shot damage is sub-micron in size. Because the pulses arrive faster than energy can diffuse out of the focal volume, multiple shot damage with this laser is thermal in nature. Successive pulses add more and more heat to the sample, melting a micron-sized volume. Using this thermal machining, we have written single-mode waveguides... Read more about Femtosecond laser micromachining of bulk glass at oscillator energies

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