If I have a laser source that is 90-95% linearly polarized will the other 5-10% be transmitted through a half wave-plate? Will the exiting beam be 100% polarized in the same direction? From my understanding both will just be rotated half a wave (pi/2), but won't be perfectly lined up. Thanks for any help.
- A $\lambda/2$-wave plate merely rotates the field direction. It's not a polarizer.
- A wave of arbitrary polarization (linear, circular, elliptical) can be decomposed into two linear polarized waves by projection onto the $x$ and $y$ axis (assuming that the wave propagates along $z$). Hence, the different polarizations differ "only" in how the two amplitudes $A_x, A_y$ change with time. Any wave plate ($\lambda/4$, $\lambda/2$) will act on each component separately. Hence, you won't be able to "align" different polarization.
- In order to get a purely polarized wave you should throw aways the "wrongly" polarized wave by using a polarizer.