Extinction Ratio is the ratio of transmitted power with only p polarized incident light to the transmitted power with only s polarized incident light. ARO determines extinction ratio by performing separate measurements of s and p polarized light transmittance in our spectrophotometers.
It is important to note that ARO thin film polarizers must be tilt tuned in order to optimize their performance. In other words, the angle of incidence of each individual unit must be adjusted within a small range in order to achieve best performance. The published extinction ratio specification refers to performance at this optimum angle, rather than at the nominal.