Laser Research Project

Hi everyone,

I am currently involved in research project in a University which uses laser light scattering to analyse fibrous test samples. We must first validate the system before we begin fully testing samples. In order to do this we hope to analyse 'test plates' with a known pattern. These plates will have a series of parallel vertical lines or slits (representing fibres or spacing between the fibres) of a specific thickness and spacing (eg. initial lines/slits 5 microns thick, spaced 5 microns apart with another plate with 10 micron lines/slits spaced 5 microns apart etc.). Are there such accessories available in specific dimensions? Is what I am looking for a diffraction grating which I have seen discussed?

Further background: We will shine a laser through a fibrous sample and the resulting light will deflect orthogonally to the central axis of the fibre and the resulting scatter pattern can tell us the fibre orientation. We have a red 633nm HeNe 5mW laser.

Apologies if these are simple questions, I have no background in lasers before this project so there is a bit of a learning curve with stuff like this.

Kind regards,
Robbie

This may help.
must warn the music in the intro is very odd lol

If your fibrous samples are consistent and linear (woven, for example), they should exhibit a diffraction pattern when a laser is shined through them, if the fiber spacing is in the micron range. There are lots of equations available to predict the spacing of the diffraction orders. They are a function of slits per unit length, and laser wavelength. Conversely, you can also calculate the slit density (fiber density or fiber spacing) if you know the laser's wavelength, and the diffraction order spacing.

I've made a thread on a similar subject here:
http://laserpointerforums.com/f44/make-your-own-laser-spectrometer-62605.html#post890672

Rearrange the formulas as needed.

Sorry for the delay in replying, I have been busy with a number of side projects.

Thanks for the responses and yes that is some of the most dated music I have ever heard at the beginning of the first video!

Yes I have seen a good bit on the predicting slit density etc. and I'll keep looking into it for anything that may benefit me. Initially, I still need something to prove that my laser system (mainly the image processing code I have developed) is giving good results, and hence I would like a test sample with a simplified pattern but similar scales to that I will be using.

I have talked to a number of companies which are yet to recommend anything that fits the bill so I may have to settle for the next best I can find.

Alas the search goes on.

Thanks for your help guys! Appreciated!

Sound like you are looking for a diffractive optical element (DOE) or a volume Bragg grating for your test sample.