I'm famous!

www.engineering.leeds.ac.uk

New grant

Leeds has just become part of a UK collaboration to make the world's first ever silicon-based quantum cascade laser.  I researched the theory of Si-based QCLs for my PhD, so hopefully I can contribute something to the new project...

Imaging plots

My experiments generate image data in three columns: (x, y, brightness)

Converting the raw data into a pretty image was always a slightly tedious task, as I used GNU Octave (or MATLAB) to generate the plot

function plot_3column_data(filename)
%   Grab data from file
data_from_file=load(filename);
x=data_from_file(:,1);
y=data_from_file(:,2);
z=data_from_file(:,3);

%   Find range of x and y axes and make arrays of axis data for plot
xmin=min(x);
xmax=max(x);
ymin=min(y);
ymax=max(y);
xstep=x(2)-x(1);
x_plot=[xmin:xstep:xmax];
y_plot=[ymin:xstep:ymax];

%   Reshape data column into a matrix
z_plot=reshape(z,length(x_plot),length(y_plot));

%   Finally, make a surface plot of the data, using a
%   chosen colour scheme and tweak the shape of the
%   axes
surface(x_plot,y_plot,z_plot','EdgeColor','None')
colormap bone
axis equal

Note that this fairly laborious script didn't even contain axis labelling or exporting to a PNG image. The trouble is, I think, that Octave is a very powerful matrix manipulation language and using it just as an image plotter is overkill. The script is ugly and the interpreter is pretty slow to load.

I'm sure there are much better ways to do this in Octave, but there are already some very nice ready-made data plotting tools available. I found that Gnuplot has a built-in "image" plot style, which does exactly what I want:

set terminal png transparent large size 800,600
set output 'image.png'
plot 'data.dat' with image

It's very simple, and very fast :)

Liquid helium

It's surprising how long a sealed dewar of liquid helium lasts. I opened and measured a three-week-old 120 litre dewar today and found 107 litres still inside.

Hi

Hi, I'm a research assistant in optoelectronics at the University of Leeds, and I thought I'd try something new with my research notekeeping here.

Most of the notes a scientific researcher makes are, frankly, pretty uninteresting to anyone else; they document the meticulous preparation of experiments, and countless dead ends. Every so often, the work pays off and some conclusive results are revealed, which can be published in journals or presented at conferences.

My aim here is to cover some of the middle-ground; the semi-interesting things that pop up along the way. Obviously, I won't be giving away any confidential material before I publish it. Instead, expect to find notes on experimental techniques and curiosities and my personal musings. This might be of some interest to other research scientists and engineers... maybe...