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TOPIC: Question about amplitude modulation

Question about amplitude modulation 2 years 3 months ago #79

  • sanjiv
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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
Last Edit: 2 years 3 months ago by sebastien.popoff.

Question about amplitude modulation 2 years 3 months ago #80

  • sebastien.popoff
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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.

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