Light is elliptically polarized with the ellipse diameters along x and y axes, when Ax = Ay and A is equal to ±n/2.
The electric field vector can be expressed as:
and along x and y:
ax = |Ax| cos [2П(г — ct) + фх]
ay =T| Ay | sin A(r — ct) + фx
If | Ax | = | Ay | and фу — фx = n/2 light is still elliptically polarized even if with axes not coinciding with the coordinate axes. See a summary of all these cases in Fig.3.4.