Controlling SP2150i monochromator with Python/PyVisa

Monochromator is used in optics research where a narrow bandwidth of light is required to be illuminated on a sample. I work with Princeton Instruments Acton SP2150i and needed a python program to control it. I found the manual here and on page 9-10, I saw the serial commands for various functions (such as changing filters, moving … Read more

Installing Meep 1.2 on ubuntu

Pre-compiled Meep binaries for meep1.1 exist for Ubuntu distribution. This makes it very easy to install meep on ubuntu using “apt-get install” command or from the ubuntu software center. However recently, Meep developers have release meep1.2 which has more functions compared to meep1.1. I have recently installed meep1.2 from source on ubuntu 12.04 using the … Read more

Electric field at localized plasmon resonance using MEEP

This article is about simulating localized plasmon resonances in metal nanospheres using MEEP package. Generally, I am interested in solving three problems in LSPR systems: Calculate the extinction, scattering, absorption spectra of metal nanoparticle The procedure for doing this is very similar to the method I mentioned here. Calculating the electric field enhancement spatially as … Read more

Parallelization in Octave using parcellfun/pararrayfun

My computer has many processors and I would like to run some octave scripts so that all the processors are being used. One can use octave function called “pararrayfun” for this purpose. This function is part of “general” package on octave-forge. On my ubuntu 11.10, I used “sudo apt-get install octave-general” to install this package … Read more

van der Pauw correction factor

The van der Pauw Method is a technique commonly used to measure the Resistivity and the Hall Coefficient of a sample. A correction factor goes into calculating the resistivity as described in van der Pauw paper. A iterative method is generally used to calculate the correction factor and this correction factor is plotted in Figure … Read more

Surface plasmon dispersion relation for thin metal films

[latexpage] A thin metal film in dielectric (also known as dielectric-metal-dielectric configuration) can support surface plasmons that are different in nature to the ones observed in thick metal-dielectric interfaces. Unlike, a single mode that is observed in thick metal film, thin metal films exhibit two types of modes for the same wavevector due to excitation … Read more

All entries of array except certain indices in octave/matlab

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 achieved by: b=a(1:end~=2&1:end~=4); The result is: b =    10   … Read more