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  • 1
    Electronic Resource
    Electronic Resource
    High-intensity ultraviolet laser interaction with a metallic filament (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 557-563 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results of research conducted on interaction of high-intensity ultraviolet pulsed KrF laser radiation with a metallic filament in atmospheric air are reported. Experimental results are presented on the time dependent material ejection dynamics associated with pulsed single shot focused excimer laser beams interacting with a small diameter wire. Copper wire 75 μm in diameter was illuminated with a KrF (λ=248 nm, pulse duration =17 ns full width at half-maximum) excimer laser at an irradiance of 80 GW/cm2. Interaction dynamics were recorded using both real-time and double-strobed ultraviolet laser imaging techniques. Temporal and spatial evolutions of both vaporized and molten material are reported. Material observed, during two-dimensional shadow imaging, on the side opposite the incident beam (shadow side) was shown to originate from the front ablating surface without spallation of material on the shadow surface. Several spatial material emission velocities are reported utilizing two different imaging techniques. A maximum velocity of 1500 m/s was obtained for material ejected in a direction toward the ablating laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350405
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  • 2
    Electronic Resource
    Electronic Resource
    Electromagnetic fields for an irregularly shaped, near-spherical particle illuminated by a focused laser beam (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7973-7986 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical procedure is derived for the determination of the internal and external electromagnetic fields for a monochromatic beam incident upon a homogeneous particle of arbitrarily-defined shape. The procedure is best suited for the analysis of near-spherical particles (i.e., particles which deviate from a sphere by plus or minus a few tenths of a radii). Verification and demonstration calculations are presented. Also presented are calculations investigating the effect of a surface deformation on resonance excitation within an otherwise spherical particle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347493
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  • 3
    Electronic Resource
    Electronic Resource
    Excimer laser produced plasmas in copper wire targets and water droplets (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3297-3301 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Elastically scattered incident radiation (ESIR) from a copper wire target illuminated by a KrF laser pulse at λ=248 nm shows a distinct two-peak structure which is dependent on the incident energy. The time required to reach the critical electron density (nc ≈ 1.8× 1022 electrons/cm3) is estimated at 11 ns based on experimental results. Detailed ESIR characteristics for water have been reported previously by the authors. Initiation of the broadband emission for copper plasma begins at 6.5 ±1.45 ns after the arrival of the laser pulse. However, the broadband emission occurs at 11 ± 0.36 ns for water. For a diatomic substance such as water, the electron energy rapidly dissipates due to dissociation of water molecules, which is absence in a monatomic species such as copper. When the energy falls below the excitation energy of the lowest electron state for water, it becomes a subexcitation electron. Lifetimes of the subexcited electrons to the vibrational states are estimated to be of the order of 10−9 s. In addition, the ionization potential of copper (440–530 nm) is approximately 6 eV, which is about two times smaller than the 13 eV ionization potential reported for water. The higher ionization potential contributes to the longer observed delay time for plasma formation in water. After initiation, a longer time is required for copper plasma to reach its peak value. This time delay in reaching the maximum intensity is attributed to the energy loss during the interband transition in copper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357451
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  • 4
    Electronic Resource
    Electronic Resource
    Internal fields of a spherical particle illuminated by a tightly focused laser beam: Focal point positioning effects at resonance (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2900-2906 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spherical particle/arbitrary beam interaction theory developed in an earlier paper is used to investigate the dependence of structural resonance behavior on focal point positioning for a spherical particle illuminated by a tightly focused (beam diameter less than sphere diameter), linearly polarized, Gaussian-profiled laser beam. Calculations of absorption efficiency and distributions of normalized source function (electric field magnitude) are presented as a function of focal point positioning for a particle with a complex relative index of refraction of n¯=1.33+5.0×10−6i and a size parameter of α≈29.5 at both nonresonance and resonance conditions. The results of the calculations indicate that structural resonances are not excited during the on-center focal point positioning of such a tightly focused beam but structural resonances can be excited by proper on-edge focal point positioning. Electric wave resonances were found to be excited by moving the focal point from on-center towards the edge of the sphere parallel to the direction of the incident beam electric field polarization. Magnetic wave resonances were found to be excited by moving the focal point from on-center towards the edge of the sphere perpendicular to the direction of the incident beam electric field polarization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342736
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  • 5
    Electronic Resource
    Electronic Resource
    Internal and near-surface electromagnetic fields for a spherical particle irradiated by a focused laser beam (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1632-1639 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Theoretical expressions for the internal and external electromagnetic fields for an arbitrary electromagnetic beam incident upon a homogeneous spherical particle are derived, and numerical calculations based upon this theoretical development are presented. In particular, spatial distributions of the internal and near-surface electric field magnitude (source function) for a focused fundamental (TEM00 mode) Gaussian beam of 1.06 μm wavelength and 4 μm beam waist diameter incident upon a 5-μm-diam water droplet in air are presented as a function of the location of the beam focal point relative to the sphere center. The calculations indicate that the internal and near-surface electric field magnitude distribution can be strongly dependent upon relative focal point positioning and may differ significantly from the corresponding electric field magnitude distribution expected from plane-wave irradiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341811
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  • 6
    Electronic Resource
    Electronic Resource
    Measurement of hypersonic velocities resulting from the laser-induced breakdown of aerosols using an excimer laser imaging system (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 3688-3691 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article we describe a dual-pulse excimer-laser-based imaging system used in the determination of ejected material velocities resulting from the interaction of KrF laser radiation (λ=248 nm, pulse width FWHM=17 ns, I≈1011 W/cm2) with 20-μm aluminum particles under vacuum (P=10−5 Torr) conditions. Material velocities measured 200–400 ns after arrival of the incident pulse ranged from 450 to 1200 m/s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141074
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  • 7
    Electronic Resource
    Electronic Resource
    Femtosecond thermomodulation measurements of Co/Cu and Ag/Cu multilayer films (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 249-251 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Femtosecond transient reflectivities of Co/Cu and Ag/Cu multilayer films were measured to study the electron-lattice relaxation in these systems. The measurement results suggest that the thickness of Cu layers does not influence the electron relaxation time. A slow decaying signal, which is absent in Ag/Cu films, was observed in Co/Cu films and it is attributed to the spin excitations in the Co layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108980
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  • 8
    Electronic Resource
    Electronic Resource
    High intensity femtosecond laser pump-probing measurements of a Cu surface (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3726-3728 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Both the time and pumping power dependences of the reflectivity of a Cu surface were measured. The role of free electrons and the d-band electrons in the time dependent reflectivity changes are analyzed. Theoretical calculations based on a d-band transition model have been performed to describe the power dependence of the reflectivity changes. Results suggest that d-band electron transitions play an important role especially at early times and low pumping intensities. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115363
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  • 9
    Electronic Resource
    Electronic Resource
    Theoretical determination of net radiation force and torque for a spherical particle illuminated by a focused laser beam (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4594-4602 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Series expressions for the net radiation force and torque for a spherical particle illuminated by an arbitrarily defined monochromatic beam are derived utilizing the spherical-particle/arbitrary-beam interaction theory developed in an earlier paper. Calculations of net force and torque are presented for a 5-μm-diam water droplet in air optically levitated by a tightly focused (2 μm beam waist diameter) TEM00-mode argon-ion (λ=0.5145 μm) laser beam for on and off propagation axis, and on and off structural resonance conditions. Several features of these theoretical results are related to corresponding experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343813
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  • 10
    Electronic Resource
    Electronic Resource
    Interactions of intense ultraviolet laser radiation with solid aerosols (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 2283-2288 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Characterizations of the interaction of intense ultraviolet laser radiation (λ=248 nm) with small solid aerosols are presented. Interaction dynamics, velocity measurements of expelled material, and thresholds for plasma formation are presented for aluminum, calcium fluoride, glass, silicon carbide, and tungsten particles. An excimer laser operating with a krypton fluoride gas mixture was used to irradiate small solid aerosol particles (≈5–50 μm) under atmospheric and vacuum conditions down to 10−5 Torr. Focused laser radiation intensities varied from 107 W/cm2 to a maximum of 2×1011 W/cm2. Interactions of the laser radiation with the solid aerosols were recorded in real time by an ultraviolet laser imaging system. Velocities between 250 and 2000 m/s were measured for material ejected from particles undergoing laser interaction. Laser intensity thresholds for visible plasma emission ranged from a maximum of 650 MW/cm2 for aluminum to a minimum of 59 MW/cm2 for tungsten. Thresholds for plasma formation were determined to be relatively independent of ambient pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345522
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