10 research outputs found
Nanomesh:A Python workflow tool for generating meshes from image data
Create 2d and 3d meshes from experimental imaging data.</p
Uniform line fillings
Deterministic fabrication of random metamaterials requires filling of a space
with randomly oriented and randomly positioned chords with an on-average
homogenous density and orientation, which is a nontrivial task. We describe a
method to generate fillings with such chords, lines that run from edge to edge
of the space, in any dimension. We prove that the method leads to random but
on-average homogeneous and rotationally invariant fillings of circles, balls
and arbitrary-dimensional hyperballs from which other shapes such as rectangles
and cuboids can be cut. We briefly sketch the historic context of Bertrand's
paradox and Jaynes' solution by the principle of maximum ignorance. We analyse
the statistical properties of the produced fillings, mapping out the density
profile and the line-length distribution and comparing them to analytic
expressions. We study the characteristic dimensions of the space in between the
chords by determining the largest enclosed circles and balls in this pore
space, finding a lognormal distribution of the pore sizes. We apply the
algorithm to the direct-laser-writing fabrication design of optical
multiple-scattering samples as three-dimensional cubes of random but
homogeneously positioned and oriented chords.Comment: 10 pages, 12 figures; v3: restructured paper, more references, more
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Data: Non-utopian optical properties computed of a tomographically reconstructed real photonic band gap crystal
<p>This repository contains the scripts and data used for the manuscript "Non-utopian optical properties computed of a tomographically reconstructed real photonic band gap crystal'' by LJ Corbijn van Willenswaard, S Smeets, N Renaud, M Schlottbom, JJW van der Vegt and WL Vos</p>
<p>This dataset contains the following:</p>
<ul>
<li>The starting slice of the X-ray holotomagraphy dataset</li>
<li> All data generated that is used in the paper including:
<ul>
<li>X-ray processing results</li>
<li>Raw results from the computations</li>
<li>Post processed results that are the basis of the manuscript</li>
</ul>
</li>
<li>All scripts that were used to automate this process</li>
<li>A copy of:
<ul>
<li>Nanomesh repository (for x-ray processing)</li>
<li>hpgem & DGMax source code (for the computations)</li>
</ul>
</li>
</ul>
<p>A more detailed readme is included with the data.</p>
Computation of Optical Properties of Real Photonic Band Gap Crystals as Opposed to Utopian Ones
Computational methods are essential in the design and analysis of three-dimensional (3D) photonic crystals [1]. These methods predict the physical properties of a particular design before elaborate nanomanufacturing. However, any manufactured crystal device inevitably differs from the design [2], [3]. These differences are not included in modelled crystals that we therefore call “utopian”, which are typically assumed to be infinite for computational reasons. Therefore, the inevitable differences between experimental measurements and theoretical predictions can be explained by two sources, the imperfect model and the effects of manufacturing. The central problem is that the current knowledge and methods are not sufficient for attributing the differences to either cause, which hampers a systematic approach to improving device performance and thus device applications. Here, we aim to improve the understanding of manufacturing effects by using the structure of a real photonic crystal as input for computations, thereby including all real manufacturing defects
Non-utopian optical properties computed of a tomographically reconstructed real photonic band gap crystal
State-of-the-art computational methods combined with common idealized structural models provide an incomplete understanding of experiments on real nanostructures, since manufacturing introduces unavoidable deviations from the design. We propose to close this knowledge gap by using the real structure of a manufactured crystal as input in computations to obtain a realistic comparison with observations on the same nanostructure. We demonstrate this approach on the structure of a real silicon inverse woodpile photonic bandgap crystal, obtained by previous synchrotron X-ray imaging. A 2D part of the dataset is selected and processed into a computational mesh suitable for a Discontinuous Galerkin Finite Element Method (DGFEM) to compute optical transmission spectra that are compared to those of a utopian crystal, i.e., a hypothetical model crystal with the same filling fraction where all pores are identical and circular. The nanopore shapes in the real crystal differ in a complex way from utopian pores, leading to a complex transmission spectrum with significant frequency speckle in and beyond the gap. The utopian model provides only a limited understanding of the spectrum: while it accurately predicts low frequency finite-size fringes and the lower band edge, the upper band edge is off, it completely misses the presence of speckle, the domination of speckle above the gap, and possible Anderson localized states in the gap. Moreover, unlike experiments where only external probes are available, numerical methods allow to study all fields everywhere. While the pore shapes hardly affect the fields at low frequency, major differences occur at high frequency such as localized fields deep inside the real crystal. In summary, using only external measurements and utopian models may give an erroneous picture of the fields and the LDOS inside a real crystal, which is remedied by our new approach