Modeling of astigmatic-elliptical beam shaping during fs-laser waveguide writing including beam truncation and diffraction effects

Tailored intensity profiles within the focal spot of the laser beam offer great potential for a well-defined control of the interaction process between laser radiation and material, and thus for improving the processing results. The present paper discusses a novel refractive beam-shaping element that provides different squared intensity distributions converted from the Gaussian output beam of the utilized femtosecond (fs) laser. Using the examples of surface structuring of stainless-steel on the micro- and nano-scale, the suitability of the beam-shaping element for fs-laser material processing with a conventional f-Theta lens is demonstrated. In this context, it was shown that the experimental structuring results are in good agreement with beam profile measurements and numerical simulations of the beam-shaping unit. In addition, the experimental results reveal the improvement of laser processing in terms of a significantly reduced processing time during surface nano-structuring and the possibility to control the ablation geometry during the fabrication of micro-channels.

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Diffraction effects in laser beam shaping systems

10.1117/12.2191293 ◽

2015 ◽

Author(s):

S. Schmidt ◽

U. Lippmann ◽

M. M. Guenther ◽

H. Gross

Keyword(s):

Laser Beam ◽

Beam Shaping ◽

Laser Beam Shaping ◽

Diffraction Effects

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Independent control of beam astigmatism and ellipticity using a SLM for fs-laser waveguide writing

Optics Express ◽

10.1364/oe.17.020853 ◽

2009 ◽

Vol 17 (23) ◽

pp. 20853 ◽

Cited By ~ 18

Author(s):

A. Ruiz de la Cruz ◽

A. Ferrer ◽

W. Gawelda ◽

D. Puerto ◽

M. Galván Sosa ◽

...

Keyword(s):

Independent Control ◽

Laser Waveguide ◽

Fs Laser

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Discovery and Measurement of Double Stars by Lunar Occultations

International Astronomical Union Colloquium ◽

10.1017/s0252921100027445 ◽

1965 ◽

Vol 5 ◽

pp. 28-37

Author(s):

R. Edward Nather ◽

David S. Evans

Keyword(s):

The Moon ◽

Double Stars ◽

Stellar Diameters ◽

Diffraction Effects

When a star is occulted by the dark limb of the Moon its apparent intensity drops to zero very quickly. MacMahon (1909) proposed that the time of disappearance would measure the diameter of the star, but Eddington (1909) demonstrated that diffraction effects at the lunar limb would lengthen the apparent time of disappearance to about 20 msec, and suggested that these effects would greatly limit the usefulness of the technique. MacMahon’s paper indicates that he was aware that stellar duplicity could be detected from occultation observations, but he did not amplify the point and Eddington did not comment on it. While it has been demonstrated theoretically by Williams (1939) and experimentally by Whitford (1939) and others that stellar diameters of a few arcmsec can be measured by this technique, its use for the discovery and measurement of double stars has been only incidental to other programs (O’Keefe and Anderson, 1952; Evanset al., 1954). Properly exploited, the method can contribute materially to the study of double stars.

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Transmission Electron Diffraction Analysis by Computer

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100067194 ◽

1970 ◽

Vol 28 ◽

pp. 40-41

Author(s):

R.A. Ploc ◽

G.H. Keech

Keyword(s):

Electron Diffraction ◽

Input Data ◽

Reciprocal Lattice ◽

Computer Programme ◽

Transmission Electron Diffraction ◽

Usual Procedure ◽

Transmission Electron ◽

Complex Shapes ◽

Computer Input ◽

Diffraction Effects

An unambiguous analysis of transmission electron diffraction effects requires two samplings of the reciprocal lattice (RL). However, extracting definitive information from the patterns is difficult even for a general orthorhombic case. The usual procedure has been to deduce the approximate variables controlling the formation of the patterns from qualitative observations. Our present purpose is to illustrate two applications of a computer programme written for the analysis of transmission, selected area diffraction (SAD) patterns; the studies of RL spot shapes and epitaxy.When a specimen contains fine structure the RL spots become complex shapes with extensions in one or more directions. If the number and directions of these extensions can be estimated from an SAD pattern the exact spot shape can be determined by a series of refinements of the computer input data.

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Characteristic Geometry and Diffraction Contrast of Dispersed ThO2 Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100062750 ◽

1969 ◽

Vol 27 ◽

pp. 168-169

Author(s):

R. J. Horylev ◽

L. E. Murr

Keyword(s):

Dark Field ◽

Particle Orientation ◽

Contrast Effects ◽

Strain Fields ◽

Diffraction Contrast ◽

Dispersed Particles ◽

Field Electron Microscopy ◽

Dark Field Electron ◽

Particle Images ◽

Diffraction Effects

Smith has shown by dark-field electron microscopy of extracted ThO2 particles from TD-nickel (2% ThO2) that they possess single crystal characteristics. It is generally assumed that these particle dispersions are incoherent. However, some diffraction effects associated with the particle images appeared to be similar to coherency strain fields. The present work will demonstrate conclusively that ThO2 dispersed particles in TD-nickel (2% ThO2) and TD-NiCr (2% ThO2, 20% Cr, Ni) are single crystals. Moreover, the diffraction contrast effects are extinction fringes. That is, these effects arise because of the particle orientation with respect to the electron beam and the extinction conditions for various operating reflections The particles are in fact incoherent.

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Diffraction effects from inclined grain boundaries in polycrystalline thin foils

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109240 ◽

1978 ◽

Vol 36 (1) ◽

pp. 420-421

Author(s):

C.B. Carter ◽

A.M. Donald ◽

S.L. Sass

Keyword(s):

Thin Film ◽

Grain Boundaries ◽

Boundary Plane ◽

Foil Surface ◽

Thin Foils ◽

The Matrix ◽

Firm Basis ◽

Diffraction Patterns ◽

Wave Matching ◽

Diffraction Effects

Using thin-film gold bicrystals with the boundary plane parallel to the foil surface, it has been shown(l,2) that networks of grain boundary dislocations can act as diffraction gratings and give rise to subsidiary reflections close to the matrix reflections in electron diffraction patterns. Recently several groups of workers(3-5) have shown that inclined boundaries in polycrystalline specimens also produce extra reflections which may be due to the periodic nature of the boundaries. In general grain boundaries in polycrystalline specimens will be steeply inclined to the foil surface and additional reflections due to wave matching at the boundary(6) will also be present. The diffraction technique has the potential for providing detailed information on the structure of inclined boundaries (see, for example (5)), especially for the case where the image contains no useful information. In order to provide a firm basis for this technique, the geometry of the diffraction effects expected from inclined boundaries and the influence of these effects on the appearance of images will be examined.

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