Hi I am using a HoloEye Phase only SLM. I would like to illuminate my scattering medium using a line illumination.

For which I made a collimated laser beam. Then used a cylindrical lens to get line illumination on the SLM. Out of 1920x1080 pixels I want the phase variation only in the 960th column. For I which I created a phase mask with only enteries in the 960th column and loaded ito to the SLM. And this is the illumination that I want on my scattering medium. Unfortuately I get the light reflected from the SLM completely. How can I make sure that SLM reflects only the line I loaded?

Please can you help me
Sanjeev

Dear Sanjeev,

You use a phase modulator, so when you illuminate it with light at the working polarization, if you change the value of the pixels, you cannot directly switch off the amplitude after the SLM, you can only modulate the phase.

That being said, as I already replied to your previous post, you can use polarizers to obtain amplitude modulation. At the working polarization (usually horizontal) you change the value \phi of the phase by tuning the value of the pixels. At the orthogonal polarization, you do not change the phase nor the amplitude. If you arrive at 45 degrees, after modulation by the SLM, you have a phase difference \phi between the horizontal and vertical polarizations. If you project back to a +/-45 degree polarization, you have a field in cos(\alpha). Then you have your amplitude modulation.

Sebastien

Dear Sebastien,

I am trying to implement amplitude modulation with a phase only SLM. Is there any paper that can help me to get a visual description of the setup that you have mentioned, or is there anything that might help to understand the basic principle behind the phase SLM working as an intensity modulator.

Many thanks in advance
Saswata

Hi Saswata,

For amplitude modulation using polarizers, you can look at this tutorial:
How to calibrate linearly aligned nematic liquid crystal based SLMs
and replace the photodetector with a camera to observe your amplitude patterns.

Hello Sebastien,

Many thanks for sharing the tutorial.

It has helped me a lot.

Yours Sincerely
Saswata Mukherjee

Hello Sanjiv,

I hope you people are doing well there.
Can you please suggest how to program a particular single pixel of the SLM using Matlab-SDK. Any response will be appreciable and I will be very thankful to you.

Regards,
Faheem

Hi Faheem,

Your question is not clear, what Matlab-SDK are you talking about? What do you mean by "program a particular single pixel of the SLM"?

I do not use Matlab anymore but this tutorial used to work for controlling an SLM with Matlab:
How to control an SLM with Matlab/Octave using Psychtoolbox