# Polarization & Photons

Published on: Sat Mar 05 2011

Polarization is the orientation of the oscillations of the particles composing a transverse wave.  The particles could be oscillating in an up down pattern solely along a single axis or they could be experiencing oscillations along both the y and z axis at the same time, while the wave propagates down the x axis. Because of the different oscillation patterns there is linear, circular or elliptical polarization of light.

Light may consist of many plane waves with different polarizations, making it appear that the light is non-polarized. Filters can be used to separate out plane waves with different orientations of polarization. The reason a filter works is that a horizontally polarized plane wave cannot pass through a vertical slit, and vice versa.

Interference is the phenomena where two light waves are at different phases and cancel/amplify each other, creating a pattern of stripes. Interference patterns appear when a single light beam is split into two beams, and one of the beams takes a slightly longer path before recombining with the original beam, causing a phase difference in the superposition beam.

A half wave plate reverses the direction of polarization of a light beam. For example, if light is filtered so that the beam in oscillating along a +45 degree angle (to the Normal), once it is passed through a half wave plate it will be oscillating along a -45 degree angle (to the normal).

A wave plate works by shifting the phase between the two polarization components of a light wave, so in a sense it is phase shifting the light beam as well.

If a single beam is linearly polarized, then split in two and one half of the beam is phase offset by taking a slightly longer path, there is an interference pattern.

Does adding a half wave plate remove the interference pattern?

Does then adding another phase offset bring it back?