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Jonathan Lawrence - One of the best experts on this subject based on the ideXlab platform.

  • An analysis of the beam interaction characteristics of selected lasers with an alpha-alumina bioceramic
    Optics and Lasers in Engineering, 2004
    Co-Authors: Jonathan Lawrence
    Abstract:

    Abstract Certain differences between the interaction characteristics of a CO2 laser, a Nd:YAG laser and a high power diode laser with an alpha-alumina bioceramic have been investigated. For each laser the fluence threshold values at which significant material removal occurs were found graphically. Through the implementation of a derivative of Beer–Lambert's law, the laser beam Absorption Lengths were calculated along with the thermal loading values. An examination of the laser-induced meltpool propagation in the alpha-alumina revealed good agreement with the Stefan solution to the heat diffusion equation for the lasers. Absorptivity measurements revealed that there was no correlation between the actual absorptivity of the alpha-alumina and the Absorption Length for each of the three lasers on account of the absorptivity measurements being similar for each laser. However, differences in the depth of melting experienced by the alpha-alumina meant that it is reasonable to assume that Absorption Length is the principal influence on the melt depth.

  • Determination of the Absorption Length of CO2, Nd:YAG and high power diode laser radiation for a selected grouting material
    Applied Surface Science, 2002
    Co-Authors: Jonathan Lawrence, K Minami, Roger E. Edwards, Andrew W Gale
    Abstract:

    Abstract The laser beam Absorption Lengths of CO2, Nd:YAG and a high power diode laser (HPDL) radiation for a newly developed SiO2/Al2O3-based tile grout have been determined through the application of Beer–Lambert’s law. The findings revealed marked differences in the Absorption Lengths despite the material having similar beam Absorption coefficients for the lasers. The Absorption Lengths for the SiO2/Al2O3-based tile grout for CO2, Nd:YAG and HPDL radiation were calculated as being 232±11, 193±4 and 183±8 μm , respectively. Moreover, this method of laser beam Absorption Length determination, which has hitherto been used predominantly with lasers operated in the pulsed mode, is shown to be valid for use with lasers operated in the continuous wave (CW) mode, depending upon the material being treated.

  • Determination of the Absorption Length of CO2 and high power diode laser radiation for a high volume alumina-based refractory material
    Applied Surface Science, 2000
    Co-Authors: Jonathan Lawrence
    Abstract:

    Abstract The laser beam Absorption Lengths of CO 2 (10.6 μm waveLength) and a high power diode laser (HPDL) (810 nm waveLength) radiation for an Al 2 O 3 /SiO 2 -based refractory have been determined through the application of Beer–Lambert’s law. The findings revealed marked differences in the Absorption Lengths despite the material having similar beam Absorption coefficients for both lasers. The Absorption Lengths for the Al 2 O 3 /SiO 2 -based refractory of CO 2 and a HPDL radiation were calculated as being 345±22 and 198±15 μm, respectively. Moreover, this method of laser beam Absorption Length determination, which has hitherto been used predominantly with lasers operated in the pulsed mode, is shown to be valid for use with lasers operated in the continuous wave (CW) mode, depending upon the material being treated.

  • Determination of Absorption Length of CO2 and high-power diode laser radiation for ordinary Portland cement
    Journal of Physics D, 2000
    Co-Authors: Jonathan Lawrence, Emma P. Johnston
    Abstract:

    The laser beam Absorption Lengths of CO2 laser and a high-power diode laser (HPDL) radiation for the ordinary Portland cement (OPC) surface of concrete have been determined. By employing Beer-Lambert's law the Absorption Lengths for concrete of the CO2 laser and the HPDL radiation were 470±22 µm and 177±15 µm, respectively.

Thomas F Deutsch - One of the best experts on this subject based on the ideXlab platform.

  • co mgf 2 laser ablation of tissue effect of waveLength on ablation threshold and thermal damage
    Conference on Lasers and Electro-Optics, 1991
    Co-Authors: Kevin T. Schomacker, Thomas J Flotte, Yacov Domankevitz, Thomas F Deutsch
    Abstract:

    The waveLength dependence of the ablation threshold of a variety of tissues has been studied using a tunable pulsed Co:MgF2 laser in order to determine how closely it tracks the optical Absorption Length of water. The Co:MgF2 laser was optically pumped by a Nd:YAG laser emitting at 1.338 μm. Typical output energies were 70 μJ in a train of 2-JAS pulses approximately 100 μs long. The Co:MgF2 laser was tuned between 1.81 and 2.14 μm, a waveLength region in which the Absorption Length varies by a decade.

  • co mgf2 laser ablation of tissue effect of waveLength on ablation threshold and thermal damage
    Lasers in Surgery and Medicine, 1991
    Co-Authors: Kevin T. Schomacker, Thomas J Flotte, Yacov Domankevitz, Thomas F Deutsch
    Abstract:

    Abstract The waveLength dependence of the ablation threshold of a variety of tissues has been studied by using a tunable pulsed Co:MgF2 laser to determine how closely it tracks the optical Absorption Length of water. The Co:MgF2 laser was tuned between 1.81 and 2.14 microns, a waveLength region in which the Absorption Length varies by a decade. For soft tissues the ablation threshold tracks the optical Absorption Length; for bone there is little waveLength dependence, consistent with the low water content of bone. Thermal damage vs. waveLength was also studied for cornea and bone. Thermal damage to cornea has a weak waveLength dependence, while that to bone shows little waveLength dependence. Framing-camera pictures of the ablation of both cornea and liver show explosive removal of material, but differ as to the nature of the explosion.

S.i. Najafi - One of the best experts on this subject based on the ideXlab platform.

T Schreiber - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigations on the tmi thresholds of low na yb doped single mode fibers
    Optics Letters, 2018
    Co-Authors: Franz Beier, Friedrich Moller, Bettina Sattler, Johannes Nold, A Liem, Christian Hupel, Stefan Kuhn, Sigrun Hein, Nicoletta Haarlammert, T Schreiber
    Abstract:

    In this contribution we investigate the transversal mode instability behavior of a ytterbium-doped commercial 20/400 fiber and obtain 2.9 kW of output power after optimizing the influencing parameters. In this context, we evaluate the influence of the bend diameter and the pump waveLength within the scope of the Absorption Length and the Length of the fiber. Furthermore, with a newly developed fiber we report on 4.4 kW of single-mode output power at 40 cm bend diameter.

Paul W. Juodawlkis - One of the best experts on this subject based on the ideXlab platform.

  • Limits to Maximum Absorption Length in Waveguide Photodiodes
    IEEE Photonics Journal, 2011
    Co-Authors: Shannon M. Madison, Jonathan Klamkin, Douglas C. Oakley, A. Napoleone, Jason J. Plant, Paul W. Juodawlkis
    Abstract:

    The maximum photocurrent, power dissipation, and linearity of waveguide photodiodes are limited by the Length over which the input optical power is absorbed. This Absorption Length is determined by the Absorption coefficient of the absorbing layer material (αo), the optical confinement factor (Γ), and the excess loss coefficient (αi). In this paper, we analyze the fundamental limits to maximizing the Absorption Length and demonstrate a new waveguide photodiode structure that approaches these limits. The new structure is referred to as a slab-coupled optical waveguide photodiode (SCOWPD) and is realized in the InGaAsP/InP material system. Assuming 100% coupling efficiency, the SCOWPD has an ultralow optical confinement factor and a low excess loss coefficient, both calculated from measurements, of Γ = 0.069% and αi = 1.65 cm-1, respectively. This results in a 1/e Absorption Length of 2.1 mm. The SCOWPD exhibits an external responsivity of 0.8 A/W and a maximum photocurrent of 250 mA at a waveLength of 1.55 μm.