Presentations

    The role of multiphoton excitation in ultrafast white-light continuum generation, at APS Centennial Meeting 1999 (Atlanta, GA), Thursday, March 25, 1999:
    When a powerful ultrashort laser pulse is focused into a transparent medium, it can undergo severe spectral broadening and be transformed into a white-light spectral continuum. Despite the continuum's widespread use as a tunable ultrafast light source, the mechanisms of continuum generation are still poorly understood. We report an experimental investigation of white-light continuum generation in transparent media using 100-fs pulses from a Ti:sapphire laser system. We measured the continuum's spectral width for a variety of materials and pump wavelengths. The materials were selected to cover... Read more about The role of multiphoton excitation in ultrafast white-light continuum generation
    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
    Oscillator-only micromachining of transparent materials, at Photonics West 2000 (San Jose, CA), Monday, January 24, 2000:
    By focusing femtosecond laser pulses with high numerical-aperture microscope objectives, we achieve the intensities required for bulk damage in transparent materials with energies in the range of modern laser oscillators. When a femtosecond laser pulse is tightly focused inside a transparent material, energy deposition occurs only at the focus, where the laser intensity is high enough to cause absorption through nonlinear processes. When enough energy is deposited, a localized change in the index of refraction is produced, i.e. the material is damaged. By scanning the focus through the sample... Read more about Oscillator-only micromachining of transparent materials
    Interactions of Femtosecond Laser Pulses with Transparent Materials, at Physics colloquium, University of Massachusetts at Lowell (Lowell, MA), Wednesday, April 12, 2000:
    Usually when light goes through a piece of glass, nothing happens to either the light nor the glass, i.e. the glass is transparent. With a powerfull femtosecond laser pulse, however, both the laser light and the glass can be changed. We study the interaction of intense, femtosecond laser pulses with bulk transparent materials. The intensity of a tightly-focused, femtosecond laser pulse can be high enough to cause nonlinear absorption of laser energy by the transparent material. When enough energy is deposited, permanent material change results. The absorption and therefore the material... Read more about Interactions of Femtosecond Laser Pulses with Transparent Materials
    Photodisruption in turbid tissue with 100-fs and 200-ps laser pulses, at APS Centennial Meeting 1999 (Atlanta, GA), Friday, March 26, 1999:
    We compare the potential of 100-fs and 200-ps laser pulses for photodisruptive surgery on the surface and in the bulk of turbid tissue. Water, human epidermis cultures, and pig skin were used as tissue models. In our technique, tightly-focused femtosecond and picosecond laser pulses are nonlinearly absorbed, vaporizing tissue in the focal volume. We find that there are several advantages in using femtosecond pulses for photodisruption. The breakdown threshold is lower and the energy deposition is more deterministic for 100-fs pulses compared to 200-ps pulses. In human skin culture we observe... Read more about Photodisruption in turbid tissue with 100-fs and 200-ps laser pulses
    Two-Photon Absorption FROG: measuring white-light continuum pulses, at Conference on Lasers and Electro-Optics (Baltimore, MD), Monday, May 7, 2001
    We demonstrate a new type of frequency resolved optical gating using the two- photon-absorption nonlinearity. The resonant enhancement and lack of phasematching re- quirements enable the FROG measurement of ultrashort white-light continuum laser pulses.
    Microexplosions: Highly supersonic plasma expansion following femtosecond laser induced breakdown, at OSA Annual Meeting (Baltimore, MD), Thursday, October 1, 1998:
    Tightly focused ultrashort laser pulses are used to produce a hot, dense plasma in water. Using time-resolved imaging and scattering techniques we map the supersonic expansion of this plasma. The expansion reaches a speed of 90 km/s, the fastest expansion witnessed to date in laser induced breakdown. Extreme temperature and pressure drive this expansion.