Combining Quarter-Wave Plates: Effects & Differences

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Discussion Overview

The discussion revolves around the effects and differences when combining two identical quarter-wave plates, particularly focusing on their arrangement and the resulting optical properties. Participants explore theoretical implications, practical considerations, and potential experimental setups.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants suggest that placing two identical quarter-wave plates in series with aligned axes results in a half-wave plate.
  • Others question the assumption that the arrangement is straightforward, highlighting the need for clarification on what "together" means in this context.
  • Concerns are raised about the impact of distance between the plates on phase differences, with one participant proposing that a finite distance could lead to a phase delay and potential interference effects.
  • Another participant mentions that reflections from unglued plates introduce additional complexities, suggesting that this could affect the resulting optical behavior.
  • One participant introduces the concept of constructing a zero-order wave plate, indicating that this could yield different properties compared to a standard half-wave plate.

Areas of Agreement / Disagreement

Participants express differing views on the implications of distance between the plates and the resulting optical effects. There is no consensus on the effects of reflections or the definition of "together," indicating ongoing debate and exploration of the topic.

Contextual Notes

Limitations include assumptions about alignment and the effects of environmental factors such as distance and reflections, which remain unresolved in the discussion.

fermatsenigma
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If we put two identical quarter-wave plates together what will be the resulting plate? How would it be different from one of the quarter-wave plates?
 
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fermatsenigma said:
If we put two identical quarter-wave plates together what will be the resulting plate? How would it be different from one of the quarter-wave plates?

Please define "together".
 
If you put them in series with the axes aligned, you will get a half-wave plate.
 
clem said:
If you put them in series with the axes aligned, you will get a half-wave plate.
Are you sure? Have you ever tried it? Putting in series? With 1mm distance between them? Or with just a small grain of dust between them?

Y33t's question about meaning of 'together' was not so trivial...
 
Why would a distance between them affect the phase difference?
 
clem said:
Why would a distance between them affect the phase difference?

PD < wave1 < wave2

PD: propagation direction

Assume all axis are aligned, wave1 and wave2 are separated by a finite distance of d (origin of wave2 is d length right to wave1 in the PD). wave2 will travel more than wave1 in the direction of PD to reach any target along this path thus there will be a phase delay between these two waves. If there exists a target along the PD these waves will collapse and form an interference pattern on the surface. It's a modified version of the Michelson Interferometer.
 
Because of reflections.
If two plates are are not glued together with immerse fluid you have two additional reflecting planes in the middle.
 
This is the way to build a zero order wave plate, so you may have a half-wave plate or a zero order quarter wave plate. Zero order wave plate has better properties then the wave plate.
Bye the way very good question and very proper time to ask it Aug2-11
 

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