Q:

What happens to the rest of the light that didn't get filtered by polarized film?

Suppose I used a polarized film to produce say left circularly polarized light, I wonder what happens to the rest of the light that gets absorbed or reflected away? Are those unpolarized or right circularly polarized?

A:

A typical circular polarizer consists of two layers: a linear polarizer with, say, a vertical orientation; and a birefringent layer whose axis is tilted at 45 degrees.  The linear polarizer absorbs the horizontally polarized components of incident light and transmits the vertically polarized components; then the birefringent layer converts the vertically polarized transmitted light to circularly polarized light. The final polarization state is right-circularly polarized or left-circularly polarized depending on whether the 45 degree tilt is clockwise or counterclockwise.
If a reflective linear polarizer is used instead of an absorptive linear polarizer, then in the example above the reflected light is horizontally linearly polarized, and the vertically polarized light the polarizer transmits is converted to circularly polarized light by the subsequent birefringent layer.

