Why tilting a diffraction grating produces tilted dots

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Discussion Overview

The discussion revolves around the phenomenon of tilting a diffraction grating and its effect on the resulting diffraction pattern, specifically why the dots produced by the grating also tilt. Participants explore theoretical frameworks, including the Ewald sphere and the behavior of light as a superposition of plane waves, while grappling with the implications of these concepts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why tilting a diffraction grating results in tilted dots, noting that the lines remain lines when tilted and expressing confusion about the propagation of light in this context.
  • Another participant suggests that the article referenced may provide answers to the initial questions, although they express frustration over the lack of a provided reference.
  • A participant acknowledges their previous understanding of the Ewald sphere and coupled wave theory at normal incidence but indicates uncertainty about the connection between the continuity condition and the Ewald sphere.
  • One participant mentions that various theoretical configurations are discussed in the literature, but many remain unknown to non-specialists, indicating a gap in understanding among the general audience.

Areas of Agreement / Disagreement

Participants express differing levels of understanding regarding the connection between the Ewald sphere and the behavior of light in diffraction. There is no consensus on the explanation for the tilting of the dots or the implications of the continuity condition.

Contextual Notes

Some participants reference specific articles and theories, but there are limitations in the shared understanding of these concepts, particularly regarding the Ewald sphere and its application to the problem at hand.

Daniel Petka
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TL;DR
If I send a gaussian laser beam through a diffraction grating at an angle, the dots are tilted and not straight.
Why does tilting a diffraction grating tilt the dots as well? This doesn't make sense to me because the lines are still lines when tilted. Even when I consider the phase and consider the gaussian beam that comes in as a superposition of plane waves, what comes out are dots in a straight line. Thanks for any insight!

My best attempt to make sense of this is to imagine the light behind the grating as an interference of many beams (plane waves actually). Ultimately, the light "doesn't know" what happens before it, it just propagates. This works great at normal incidence, it's called the angular spectrum, but it absolutely fails when the light comes in at an angle

340_2021_7620_Fig4_HTML.png
 
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Hi,

You found the picture, so I suppose you also found the article. (Could have saved us the time to locate it by posting the reference !)

The article goes a long way to answer your questions ....

Daniel Petka said:
Why does tilting a diffraction grating tilt the dots as well? This doesn't make sense to me because the lines are still lines when tilted. Even when I consider the phase and consider the gaussian beam that comes in as a superposition of plane waves, what comes out are dots in a straight line. Thanks for any insight!

##\ ##
 
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BvU said:
Hi,

You found the picture, so I suppose you also found the article. (Could have saved us the time to locate it by posting the reference !)

The article goes a long way to answer your questions ....



##\ ##
Sorry for not including the article. The reason why I'm asking this is to understand the Ewald sphere. This is not the first article that I looked into that derives this using the Ewald sphere, so I'm kind of stuck. Forgive me, should have included that in the post. I already have the intuition for the Evald sphere and coupled wave theory at normal incidence - you don't have to worry about the continuity condition E,t1 = E,t2. It's not obvious to me why the continuity condition is connected to the Ewald sphere. That's where I'm struggling
 
Heuberger et al said:
Theories for almost any conceivable configuration other than the two mentioned above are treated in the literature (see, e.g., [2, 3]), but remain widely unknown to most non-specialists.
And I'm afraid I'm a non-specialist :wink:

Interesting topic, though !

##\ ##
 

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