All entries of array except certain indices in octave/matlab

Posted on Wed 07 December 2011 in Misc • Tagged with Matlab, octave

In Octave or Matlab, some times one needs to eliminate certain elements in an array.

For example, if

a = [10,20,30,40,50,60];

and suppose I want to create a matrix "b" such that it has all the elements of "a" except 20 and 40. This can be …

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Scattering / extinction / absorption cross-sections of silver nanowires (infinite cylinders) using meep

Posted on Wed 01 June 2011 in Plasmonics • Tagged with electromagnetism, FDTD, MEEP, octave, photonics, Plasmonics

Particles scatter and absorb electromagnetic radiation. One often needs to compare the amount of scattering/absorption/extinction for particles of different shapes, composition, sizes and incident light properties (polarization, frequency and angle). In this regard, the concept of cross-sections comes into picture. There are three types of cross-sections, 1) scattering …

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Arbitrary 2d shapes in MEEP

Posted on Tue 10 May 2011 in Plasmonics • Tagged with electromagnetism, FDTD, MEEP, octave, photonics, Plasmonics

In MEEP (1.1.1), dielectric structures are often created by constructive geometry (adding and subtracting primitive shapes). The primitive shapes that are allowed are blocks, cylinders, ellipsoids and cones. To create a complex shape, one has to decompose the geometry into these primitive shapes. Over the weekend, I was …

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Plasmonic materials in MEEP

Posted on Wed 27 April 2011 in Plasmonics • Tagged with electromagnetism, FDTD, Free Software, Matlab, MEEP, octave, photonics, Plasmonics, SERS


The aim of this post is to share my experience in incorporating dielectric function of metals such as gold and silver into MEEP (a free finite difference time domain package) code. The incorporation is not an easy task and can be daunting for the first time user.

Metals such …

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Electric Field in Metal Nanoparticle Dimers

Posted on Sat 09 April 2011 in Plasmonics • Tagged with FDTD, Molecular Machines, photonics, Plasmonics, SERS

Metal nanoparticles exhibit localized surface plasmon resonance (LSPR). One can think of LSPR as resonance of electron sea oscillations driven by incident electric field. This is similar to the way a spring-mass system attains resonance under external periodic driving force.

The result of this plasmon resonance is enhanced dipole moment …

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Charge density in metal nanoparticles at plasmon resonance

Posted on Tue 23 November 2010 in Plasmonics • Tagged with electromagnetism, FDTD, Free Software, photonics, Plasmonics

It is important to know the magnitude and distribution of electric field near the metallic nanoparticles at plasmon resonance. One can look at the electric field and say whether the plasmon mode is dipolar or higher order mode such as qudrapolar mode. At many times one is also interested to …

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Spoof Plasmons / Designer Surface Plasmons

Posted on Thu 07 October 2010 in Plasmonics • Tagged with MEEP, FDTD

Aim of this article/post: To 1) introduce the concept of Designer surface plasmons or Spoof plasmons and 2) Dispersion relations and Visualization of the fields using MEEP code. (Some of the text/simulations are taken from my paper in the area of DSPs.)

Surface Plasmons are electromagnetic waves that …

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DDSCAT and electric field at plasmon resonance

Posted on Wed 26 May 2010 in Plasmonics • Tagged with DDSCAT, electromagnetism, Free Software, Plasmonics

Discrete Dipole Approximation (DDA) is an important tool in plasmonics research. Using DDA, one can calculate scattering properties of nanoparticles at various wavelengths, polarizations and surrounding medium. The specialty of DDA is that one can calculate scattering properties of irregular shape particles (particles other than spheroids). DDA is based on …

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Nmie: Extinction, Scattering and Absorption efficiencies of multilayer nanoparticles

Posted on Tue 11 May 2010 in Plasmonics • Tagged with electromagnetism, Free Software,, Plasmonics, DDSCAT

nmie tool on This tool calculates the extinction, scattering, and absorption efficiencies of single nanoparticle (1 layer),core-shell nanoparticle (2 layer) and nanomatryushka nanoparticle (3 layer) using MIE formulation.

Since 2009, I have been a regular user of www.Nanohub.orgis a website that provides …

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Beamer Themes

Posted on Sun 18 April 2010 in Misc • Tagged with beamer, Free Software, Latex

One can use Beamer to make high quality presentations using Latex code. To know more about beamer and its capabilities visit hereand here.

Beamer comes with a set of default templates. However,it has capability to design new themes.

Here, I will maintain a list of beamer themes shared …

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