How is diffraction affected by grating thickness?

[Daniel.Kovacs]

I would like to talk to someone here who has either theoretical or practical experience with not-too-thin transmission gratings.

I have the following problem. I want to compute the far-field diffraction image of an electromagnetic wave (with a wavelength in the visible spectrum) as it passes through a diffraction grating which is 3-5 wavelengths (1-2 micrometers) thick. For precision I want to use vector diffraction theory because the grating period is also a few wavelengths (few micrometers) in size. How does a thickness of such an extent (3-5 lambda) affect the diffraction image? Can I get reasonable result if I suppose the grating to be infinitely thin and neglect its thickness? Or the discrepancy is substantial and I should carry out a precise calculation with near-field propagation inside the holes of the grating?

I would really appreciate an answer from anyone who is competent in optics.

Thank you and have a nice day!
Daniel

 

[eljose79]

Hello Daniel,

I have both theoretical and practical experience with transmission gratings, so I would be happy to discuss your problem with you. The thickness of a grating can have a significant impact on the diffraction image, especially when it is comparable to the wavelength of the incident light.

In general, if the grating thickness is not too thin, it is important to take it into account in your calculations. Neglecting the thickness can lead to significant discrepancies in the diffraction pattern. This is because the thickness of the grating affects the phase of the diffracted light, which is crucial in determining the shape of the diffraction pattern.

For a thickness of 3-5 wavelengths, it is likely that you will need to use vector diffraction theory to get accurate results. This takes into account the polarization of the incident light and the vector nature of electromagnetic waves. Neglecting the thickness and assuming an infinitely thin grating may give you a rough idea of the diffraction pattern, but it will not be precise enough for your needs.

If you want to achieve high precision, it is best to carry out a calculation with near-field propagation inside the holes of the grating. This will take into account the effects of the grating thickness on the diffracted light. However, this may be a more complex calculation and may require specialized software or techniques.

I hope this helps answer your question. Let me know if you have any further questions or if you need any clarification on anything I've mentioned. Best of luck with your research!