• $\vec E$ is the polarization direction
• Most common form of light is randomly polarized, no preferred direction of $\vec E$ when averaged over time
• if $\vec E$ is confined to a single plane, light is linearly polarised

🗒️ Note: the polarization direction is the same as the direction of the electric field

Light can be converted from random to linear using a linear polarizer, for example a dichroic sheet

Generally a polaroid sheet which consists of PVA doped with iodine

Circular polarized light

<aside> <img src="https://prod-files-secure.s3.us-west-2.amazonaws.com/369dfa6b-d4d9-4cf2-a446-e369553b6347/cca6ec0c-18e8-4ce8-bc05-8a3ddbacb05e/Circular_polarized_light.gif" alt="https://prod-files-secure.s3.us-west-2.amazonaws.com/369dfa6b-d4d9-4cf2-a446-e369553b6347/cca6ec0c-18e8-4ce8-bc05-8a3ddbacb05e/Circular_polarized_light.gif" width="40px" /> Circular polarized light: the electric vector rotates at a constant rate, $\omega$, the same as the oscillation frequency, and at constant amplitude

</aside>

Both linear and circular are cases of the general form that is elliptical

We see that $\vec E$ rotates at constant rate $\omega$, with a major axis that is tilted at an angle $\Psi$. Unit vector $\xi$ is plane vector, and $\eta$ is the ellipticity

💃 Examples:

• Circular polarized light: $\xi =\pi/2,-\pi/2$, $\eta=1,-1$ (right or left handed) and $\psi=0$
• Linearly polarized light: $\xi=0,\pi$, $\eta=0$ and $\psi=\{0\to\pi/2\}$

🗒️ Note: The electric vector can rotate in either direction LHC and RHC

🦴 Convention: When viewed along the propagation direction, if the electric vector rates anticlockwise this is the LHC and vice versa

Light in a medium

$$ \vec E=\left [\left |\vec E\right | \sin(\theta)\,\hat i+\left |\vec E\right |\cos(\theta)\,\hat j \right ]\exp[i(\omega t-kz+\phi)] $$

Absorbers

Circular polarized light through a linear polarizer gives linearly polarized light at half intensity no matter the orientation

Types of linear absorbing polarizers

• Aligned silver in glass (for high intensities)
• Fine conducting wires(for far IR and microwaves)