Note: Apparently, a circularly polarized light can be easily achieved when a linearly polarized light is incident on a quarter-wave plate at 45° axis respect to the linearly polarized light. Is it reversible?
Hi Amir -- I'll just add one comment on reversibility based off your drawing (the previous answers were correct, of course, so I just leave this here for future searchers looking to boost their intuition on the matter): if you think of the initial linear, diagonally-polarized wave as being composed of a vertically-polarized wave and a horizontally-polarized wave oscillating in phase with each other, it's easy to understand that (in this case) the optic axis of the quarter-wave plate allowed the vertically-polarized component to emerge one quarter-wave ahead of the horizontally-polarized component, as can be seen in your attached figure. If you were to add a second quarter-wave plate at the location of your "check" mark, its optic axis would need to be aligned now instead in the horizontal direction in order to allow the horizontally-polarized component to "catch up" in phase to the vertically-polarized component and return the beam to the exact same polarization it had before. If instead, for example, you added a second quarter-wave plate whose optic axis was oriented vertically just like the first quarter-wave plate, then the vertically-polarized component would advance ahead of the horizontally-polarized component by an addition quarter of a wave in phase, leading to a total phase difference of half of a wave (this makes sense: sequentially stacking two quarter-wave plates together makes a half-wave plate). At this point, the polarization will again be linear, but the orientation of the polarization will be diagonal in the opposite direction (i.e. orthogonal to the original polarization direction). Hope this is useful to someone, ~Eric
The answer can be easily found with transmission optics as I showed detailedly in the uploaded file.
I hope my answer can help you to well understand the underlying physics.
You can find the result by using jones matrex representation and multiplye the matrix to find the answer
Many thanks Dr. Alhamdani, yes I used Jones matrices I even simulated these waves by Mathematica. But what I got as an experimental result is different from what theory explained. Because my RHCP light would strike a reflective layer then partially pass through a tissue and again reflects back. Therefore, I have RHCP and LHCP lights as reflected lights. Due to a phase shift of RHCP the superposition of these two waves are elliptically polarized.
If linearly polarized light is incident on a quarter-wave plate, one of the light's components is retarded by a quarter wavelength by the QWP, in both faces,
for instance, from face 1 the light retarded by ג/4 and when it reflected back to the face 2 (without changing in the polarization state), the light lag is also ג/4, therefore return to the first case
Dear Dr. Al Zaidi, thank you so much for your answer. I appreciate it.
Dear Amir,
Yes it reversible. Salam is fully right. Another way to say it in a more general way is to notice that your two polarisations do have the same amplitude decomposition on the axes of the quarter wave plate and that their phase delay is not dependant on the direction of propagation.
Dear Dr. Hirlimann, Thank you so much for your answer. In my experimental setup, there is a RHCP as a light source to light up a sample ( with a reflective layer), thus, RHCP and LHCP lights will reflect back ( to CCD) which, do not have the same amplitudes. My intention was to separate LHCP light from RHCP before it reachs to CCD.
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