Quarter-wave plate - creating circular polarization
The black wave here represents the electric field wave of a beam of light.
• Red and green represent the components of this electric field in two orthogonal directions.
• Linearly polarized light enters the scene from below, then enters a "quarter-wave plate", whose "fast" and "slow" axes are aligned with the red and green directions. Light slows down in the clear plate, but the red component slows down more than green. In this case, the green wave advances exactly one cycle in the plate, while the red wave advances 1 1/4 cycles.
• Due to the different phase delay in different directions, light emerges from the plate with circular polarization.
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