Obviously, the spatial light modulator (SLM) and digital micromirror device (DMD) is diffration gratings. Therefore there would be multiple diffraction orders of the created images.
Here I want to ask a general question, for these devies, more generally for diffraction gratings, what is the effect if I just capture only one diffraction order (0th diffraction order)?
I use laser as light source. I know there would be loss of intensity when only capture one difrraction order. Would this operation degrades the quality?
I guess you meant capturing the 1st order? It depends on your application and the diffraction efficiency of your SLM. One can try to increase the efficiency of phase limited SLMs the prescription given in
Preprint Rapid phase calibration and increased efficiency of a spatia...
It seems like you are interested in the reflectivity of a diffraction grating created by an SLM. There are a few factors to consider if you wish to estimate the amount of power reflected into the 0th order and the resultant beam quality:
1. The fill factor of the SLM - the SLM is typically composed of "pixels", each one is individually programmable. Between those pixels is material that may absord or delay the reflected beam, reducing the zero order power of the grating. After propagation you may see some structure or interference effects on the zero order beam profile caused by the "fill factor" of the SLM being less than 1.
2. Surface quality - an uneven or structured surface will cause diffuse reflection, reducing the 0th order power.
3. The "quality" of the grating structure imposed on to the SLM. For a phase grating, it can be shown that the optimal phase modulation is not in fact [0,pi]. The grating quality will affect how much power is diffracted into the different orders of the grating, therefore changing the power into the 0th order beam.
@Qiuliang Ye, it's not clear where you are aiming. The technology called holography describes this area deeply and in details. Using this or similar approach you might estimate possible efficiency for each of the orders for your SLM and DMD.
Diffraction on periodic structures is well described in many works on holography. With a periodic structure similar to a meander, diffraction will go in many orders. If you are only interested in modulation of the zero order, then you need to separate it and everything, starting with the plus first and minus the first. The angle of their diffraction is simply estimated using the Bragg formula. When they leave the field occupied by the zero beam, their noisy contribution to the image will disappear. It is only necessary not to forget that the meander has three main harmonics of spatial frequencies. One is inversely proportional to the period, the second to the distance between the cells, and the third to the size of the cell. You can find more detailed calculations even on the Internet. And to understand the basics of meander diffraction, viewing the first 8 pages of my study guide can help you with diffraction displacement meters and laser Doppler speed meters. It is in Russian, but the pictures in Fig. 2.1 and 2.2 are clear and simple, as well as the formulas 2.1, 2.2 and 2.3. Regards, Sergey Shoydin
I recomend you to read this discussion:
https://www.researchgate.net/post/Can_we_design_a_diffraction_grating_that_has_only_two_orders_of_diffraction
Quiliang, first it is helpful to understand there are two different sources of diffraction 1) the
Kipp Bauchert Thanks for your detailed answer. There was an old SLM in my lab from your company! Could you provide the references for your answer? I want to understand these concepts more vividly.
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