Publications

    C. B. Schaffer, J. Aus der Au, E. Mazur, and J. A. Squier. 2002. “Micromachining and material change characterization using femtosecond laser oscillators.” In . Photonics West. Publisher's VersionAbstract
    We use third harmonic generation (THG) microscopy to image waveguides and single-shot structural modifications produced in bulk glass using femtosecond laser pulses. THG microscopy reveals the internal structure of waveguides written with a femtosecond laser oscillator, and gives a three-dimensional view of the complicated morphology of the structural changes produced with single, above-threshold femtosecond pulses. We find that THG microscopy is as sensitive to refractive index change as differential interference contrast microscopy, while also offering the three-dimensional sectioning capabilities of a nonlinear microscopy technique. It is now possible to micromachine three- dimensional optical devices and to image these structures in three dimensions, all with a single femtosecond laser oscillator.
    J. B. Ashcom, C. B. Schaffer, and E. Mazur. 2002. “Numerical aperture dependence of damage and white light generation from femtosecond laser pulses in bulk fused silica.” In . Photonics West. Publisher's VersionAbstract
    The femtosecond laser has become an important tool in the micromachining of transparent materials. In particular, focusing at high numerical aperture enables structuring the bulk of materials. At low numerical aperture and comparable energy, focused femtosecond pulses result in white light or continuum generation. It has proven difficult to damage transparent materials in the bulk at low NA. We have measured the threshold energy for continuum generation and for bulk damage in fused silica for numerical apertures between 0.01 and 0.65. The threshold for continuum generation exhibits a minimum near 0.05 NA, and increases quickly near 0.1 NA. Greater than 0.25 NA, no continuum is observed. The extent of the anti-stokes pedestal in the continuum spectrum decreases strongly as the numerical aperture is increased to 0.1, emphasizing that slow focusing is important for the broadest white light spectrum. We use a sensitive light scattering technique to detect the onset of damage. We are able to produce bulk damage at all numerical apertures studied. At high numerical aperture, the damae threshold is well below the critical power for self-focusing, which allows the breakdown intensity to be determined. Below 0.25 NA, the numerical aperture dependence suggests a possible change in damage mechanism.
    J. B. Ashcom and E. Mazur. 2001. “Femtosecond laser-induced microexplosions in transparent materials.” In . LEOS 2001. Publisher's VersionAbstract
    By focusing femtosecond laser pulses with high numerical-aperture microscope objectives, we micromachine optical glass using energies that are 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, the material is damaged and a localized change in the index of refraction is produced. By scanning the focus through the sample, very precise, three-dimensional microstructuring can be achieved.
    C. B. Schaffer, A. Brodeur, J. F. Garcia, and E. Mazur. 2001. “Micromachining bulk glass by use of femtosecond laser pulses with nanojoule energy.” Opt. Lett., 26, Pp. 93–95. Publisher's VersionAbstract
    Using tightly-focused femtosecond laser pulses of just 5 nJ we produce optical breakdown and structural change in bulk transparent materials, and demonstrate micromachining of transparent materials using unamplified lasers. We present measurements of the threshold for structural change in Corning 0211 glass, as well as a study of the morphology of the structures produced by single and multiple laser pulses. At high repetition-rate, multiple pulses produce a structural change dominated by cumulative heating of the material by successive laser pulses. Using this cumulative heating effect, we write single-mode optical waveguides inside bulk glass using only a laser oscillator.
    E. Mazur and D. S. Chung. 1987. “Light-scattering from the liquid-vapor interface.” Physica, 147A, Pp. 387–406. Publisher's VersionAbstract
    This paper presents light scattering spectra from the liquid-vapor interface of water and ethanol. Both quasi-elastic (Rayleigh) scattering and inelastic (Brillouin) scattering from fluctuations at the interface are observed. The spectra were obtained using a novel Fourier transform heterodyne technique that allows one to resolve the full Rayleigh-Brillouin triplet. Capillary waves travelling in opposite directions can therefore be separated, making the present technique suitable for studying nonequilibrium effects in interfaces.
    E. Mazur, H. J. M. Hijnen, L. J. F. Hermans, and J. J. M. Beenakker. 1984. “Experiments on the influence of a magnetic field on diffusion in N2-noble gas mixtures.” Physica, 123A, Pp. 412–427. Publisher's VersionAbstract
    Experimental results are presented for the magnetic field effect on diffusion in N2-noble gas mixtures at 300 K. The data show that the polarization produced by a concentration gradient is different from the one produced in a temperature gradient and that this difference is due to a different scalar part of the polarizations.
    G. W. t Hooft, E. Mazur, J. M. Bienfait, L. J. F. Hermans, H. F. P. Knaap, and J. J. M. Beenakker. 1979. “The influence of a magnetic field on the thermal diffusion of polyatomic gas-noble gas mixtures.” Physica, 98A, Pp. 41–86. Publisher's VersionAbstract
    Experiments on the influence of a magnetic field on the thermal diffusion (Dt) have been performed. Both the transverse coefficient, (D-tr/T), as well as the difference between the longitudinal coefficients, (D-// T), were measured for binary mixtures of N2, nD2, HD and nH2 with the noble gases Ar, Ne and He and for the system pH2-Ar. For most of these systems, the results can be adequately described with the dominant angular momentum polarization of the form WJJ. For some mixtures, however, a significant contribution from a second polarization (viz. WJ) was found to be present. The results are expressed in terms of effective molecular cross sections. Using these results and those earlier obtained for the magnetic field effect on the thermal conductivity, an estimate is made about the magnitude of the Senftleben-Beenakker effect on the diffusion.

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