Hi I am working on reproducing DOPC in focusing light through scattering medium :
I am 4f imaging the surface of the phase only LCOS Holoeye SLM on to the back aperture of a objective lens and at the focal plane of the objective I have the scattering medium.
I have a confusion in the orientation of the SLM. Should we block the zero order of the SLM and work with the first order? If so I will need to put a aperture in the fourier plane that allows just +1 order to pass through. Is it the right way to do it ?

Or is there a mistake i am doing ?
Please cloud you help me understand the concept. Your tutorials are a great help for people working in this field

Hi Vijay

I have a confusion in the orientation of the SLM. Should we block the zero order of the SLM and work with the first order? If so I will need to put a aperture in the fourier plane that allows just +1 order to pass through. Is it the right way to do it?

Well, that is entirely up to you and depends on your needs.
On a typical SLM, the filling fraction is about 90-95%. If you work at the 0th order, meaning that do not do anything special, and if you have smooth phase mask to display (high spatial frequencies can be challenging due to pixel to pixel coupling), you end up with 5-10% of the light that is not modulated (for which the SLM acts as a simple mirror).
If it is OK for your experiment, no need to go further.

Then, if you want to remove that unmodulated light, you go to the first order. To do so, you add a phase ramp to your mask. Modulated light will be shifted in the Fourier plane, where you will put an aperture to reject the rest. Unmodulated light sees the SLM as a mirror, so it stays in the 0th order and is filtered out.

Important note: When I say +1 order, it DOES NOT refer to the diffractions due to the pixel pitch (leading the pixel array to act as a grating). It is the diffraction effect introduced to the phase ramp you add to the modulation.