polarizer

noun

1. One who polarizes; one who divides a group or community into two extremes.

   “a polarizer of opinions”

2. Any device that produces polarized light.

   “When the polarizers are aligned in the same direction, they block the same state of polarization, i.e. they both block horizontally polarized light, and both let the vertically polarized light through. The second polarizer therefore has no effect on the light. When the polarizers are aligned perpendicular to one another, one will block the horizontally polarized light and the other will block vertically polarized light — no light at all gets through the pair!”