Are laser diodes polarized? And if they are polarized, what is the ratio?

Yes, laser diodes are linearly polarized. Diodes are polarized parallel to the short axis for an elliptical beam. However, the polarization ratio is difficult to specify since it varies with the type of diode. For example, a typical 5mW diode can have a ratio of 400:1 or 500:1 at an NA of 0.4 and a temperature of 25°C. In general, as the optical output power increases, the ratio increases.