Effects of thermal conductivity and index of refraction variation on the inclusion dominated model of laser-induced damage

1990 ◽  
Author(s):  
M. Z. Fuka
Keyword(s):  
Thermal Conductivity ◽  
Index Of Refraction ◽  
Laser Induced Damage

iPP/CNTs Multifunctional Polymer Nanocomposite

2012 ◽  
Vol 1403 ◽  
Author(s):  
Parvathalu Kalakonda ◽  
Sabyasachi Sarkar ◽  
Erin A. Gombos ◽  
Georgi Yordanov Georgiev ◽  
Germano Iannacchione ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Mechanical Stability ◽  
Orientational Order ◽  
Multiwall Carbon Nanotubes ◽  
Chemical Properties ◽  
Polymer Nanocomposite ◽  
Hybrid Structure ◽  
Index Of Refraction ◽  
Induced Anisotropy

ABSTRACTWe present a hybrid structure of Isotactic Polypropylene (iPP) nanocomposite with multiwall carbon nanotubes (MWCNTs). The polymer component contributes to the optical properties, flexibility and integrity of the polymer film while the carbon nanotubes change the thermal and mechanical stability, electrical and thermal conductivity and sensitivity. The multifunctional characteristics of this nanocomposite material are enhanced by anisotropic organization of the nanotubes and polymer through melt shearing which provides organization of the structural constituents at the molecular, nano, and micro length scales. This results in anisotropy of the macroscopic composite film properties parallel and perpendicular to the direction of shearing. On the molecular scale, the CNTs control the arrangement of the polymer molecules in a crystal lattice. On the nanometer scale, the CNTs couple to and align with the smectic normal of the liquid crystal phase of iPP. On the micron scale and larger, the secondary polymer crystal structure is rearranged due to the pinning of the polymer at the CNT surface to form fibrillar rather than spherulitic structures. These multi-scale rearrangements affect the optical, thermal, electrical, mechanical and chemical properties of the nanocomposite film. Our findings indicate that the CNTs under shear induce a novel anisotropy to the various thermo-physical properties of the iPP/CNTs films. We introduce an approach to extract the shear induced orientational order from the thermal conductivity of the dispersed CNTs. The index of refraction of the nanocomposites was also estimated via ellipsometry and was found to decrease slightly when CNTs were added and also showed shear induced anisotropy. The comparison between the results from the different experiments methods for probing induced anisotropy by melt shearing shows that orientation in iPP/CNTs nanocomposites induces anisotropy in multiple macroscopic properties.

Birefringence in the Boundary Layer of a Rarefied Heat Conducting Gas

1977 ◽  
Vol 32 (8) ◽  
pp. 801-804
Author(s):  
H. Vestner ◽  
J. J. M. Beenakker
Keyword(s):  
Differential Equation ◽  
Thermal Conductivity ◽  
Boundary Layer ◽  
Index Of Refraction ◽  
Heat Conducting ◽  
Parallel Plates ◽  
Tensor Polarization ◽  
Angular Momenta ◽  
Rank Tensor ◽  
The Difference

Abstract In a heat conducting diatomic gas enclosed between parallel plates, the second rank tensor polarization of the rotational angular momenta is non-zero only near the plates. Therefore the gas is birefringent only in a boundary layer which is a few mean free paths thick. The birefringence is calculated with the help of a differential equation and a boundary condition for the tensor polarization. The difference in the index of refraction for light polarized parallel, respectively perpendicular to the temperature gradient is evaluated for the gases N2 and CO with the information obtained from the field effects on viscosity and on thermal conductivity, and from thermomagnetic pressure difference measurements. The effect is estimated to be of measurable size.

scholarly journals The pulsed laser damage sensitivity of optical thin films, thermal conductivity

1989 ◽  
Vol 7 (3) ◽  
pp. 433-441 ◽  
Author(s):  
Arthur H. Guenther ◽  
John K. McIver
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Flow Analysis ◽  
Pulsed Laser ◽  
Damage Threshold ◽  
Deposition Process ◽  
Film Structure ◽  
Film Research ◽  
Laser Induced Damage

Pulsed laser induced damage of optical thin films is, in general, initiated by the absorption of laser radiation by imperfections in the films or at interfaces between film layers and/or the substrate. A heat flow analysis of this process stresses the importance that the thermal conductivity of both the thin film host and that of the substrate play in establishing the laser-induced damage threshold. Unfortunately, recent work, which will be reviewed in this presentation, indicates that the thermal conductivity of thin films can be several orders of magnitude lower than that of the corresponding material in bulk form. This situation arises as a consequence of the film structure resulting principally from the deposition process. The importance of thermal conductivity will be compared to parameters such as absorption mechanisms, film materials, composition, and other variables. Its implication for the ultimate optical strength of materials and the direction in which thin film research and processing should proceed will be highlighted.

UHV-TEM studies of laser-induced damage

1991 ◽  
Vol 49 ◽  
pp. 632-633
Author(s):  
T.S. Savage ◽  
R. Ai ◽  
D. Dunn ◽  
L.D. Marks
Keyword(s):  
Surface Science ◽  
Rapid Heating ◽  
Local Heating ◽  
Routine Practice ◽  
Transmission Electron ◽  
Northwestern University ◽  
Laser Induced Damage ◽  
Set Up ◽  
Focusing Lens ◽  
Diffusion Of Impurities

The use of lasers for surface annealing, heating and/or damage has become a routine practice in the study of materials. Lasers have been closely looked at as an annealing technique for silicon and other semiconductors. They allow for local heating from a beam which can be focused and tuned to different wavelengths for specific tasks. Pulsed dye lasers allow for short, quick bursts which can allow the sample to be rapidly heated and quenched. This short, rapid heating period may be important for cases where diffusion of impurities or dopants may not be desirable.At Northwestern University, a Candela SLL - 250 pulsed dye laser, with a maximum power of 1 Joule/pulse over 350 - 400 nanoseconds, has been set up in conjunction with a Hitachi UHV-H9000 transmission electron microscope. The laser beam is introduced into the surface science chamber through a series of mirrors, a focusing lens and a six inch quartz window.

Interferometric (Fourier-Spectroscopic) Measurement of Electron Energy Distributions

1990 ◽  
Vol 48 (2) ◽  
pp. 110-111 ◽  
Author(s):  
F. Hasselbach ◽  
A. Schäfer
Keyword(s):  
Group Velocity ◽  
Wave Packets ◽  
Index Of Refraction ◽  
Electron Wave ◽  
Fringe Contrast ◽  
Faraday Cage ◽  
Optical Index ◽  
Wien Filter ◽  
Coherent Wave ◽  
Electric And Magnetic Fields

Möllenstedt and Wohland proposed in 1980 two methods for measuring the coherence lengths of electron wave packets interferometrically by observing interference fringe contrast in dependence on the longitudinal shift of the wave packets. In both cases an electron beam is split by an electron optical biprism into two coherent wave packets, and subsequently both packets travel part of their way to the interference plane in regions of different electric potential, either in a Faraday cage (Fig. 1a) or in a Wien filter (crossed electric and magnetic fields, Fig. 1b). In the Faraday cage the phase and group velocity of the upper beam (Fig.1a) is retarded or accelerated according to the cage potential. In the Wien filter the group velocity of both beams varies with its excitation while the phase velocity remains unchanged. The phase of the electron wave is not affected at all in the compensated state of the Wien filter since the electron optical index of refraction in this state equals 1 inside and outside of the Wien filter.

TEM characterization of proton-exchanged LiNbO3 optical waveguides

1986 ◽  
Vol 44 ◽  
pp. 480-481
Author(s):  
W. E. Lee
Keyword(s):  
Refractive Index ◽  
Benzoic Acid ◽  
Optical Waveguides ◽  
Total Internal Reflection ◽  
Index Of Refraction ◽  
Optical Measurements ◽  
Lithium Ions ◽  
Wide Channel ◽  
Tem Characterization

An optical waveguide consists of a several-micron wide channel with a slightly different index of refraction than the host substrate; light can be trapped in the channel by total internal reflection.Optical waveguides can be formed from single-crystal LiNbO3 using the proton exhange technique. In this technique, polished specimens are masked with polycrystal1ine chromium in such a way as to leave 3-13 μm wide channels. These are held in benzoic acid at 249°C for 5 minutes allowing protons to exchange for lithium ions within the channels causing an increase in the refractive index of the channel and creating the waveguide. Unfortunately, optical measurements often reveal a loss in waveguiding ability up to several weeks after exchange.

Microspectroscopy Using a Solid Immersion Lens

2001 ◽  
Vol 7 (S2) ◽  
pp. 148-149
Author(s):  
C.D. Poweleit ◽  
J Menéndez
Keyword(s):  
Spatial Resolution ◽  
Focal Plane ◽  
Numerical Aperture ◽  
Normal Incidence ◽  
Spot Size ◽  
Index Of Refraction ◽  
Objective Lens ◽  
Improvement Factor ◽  
Oil Immersion ◽  
Long Time

Oil immersion lenses have been used in optical microscopy for a long time. The light’s wavelength is decreased by the oil’s index of refraction n and this reduces the minimum spot size. Additionally, the oil medium allows a larger collection angle, thereby increasing the numerical aperture. The SIL is based on the same principle, but offers more flexibility because the higher index material is solid. in particular, SILs can be deployed in cryogenic environments. Using a hemispherical glass the spatial resolution is improved by a factor n with respect to the resolution obtained with the microscope’s objective lens alone. The improvement factor is equal to n2 for truncated spheres.As shown in Fig. 1, the hemisphere SIL is in contact with the sample and does not affect the position of the focal plane. The focused rays from the objective strike the lens at normal incidence, so that no refraction takes place.

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