Using three ruling engines in a controlled environment, Optometrics can rule polarisers with groove spacings up to 1200 per mm. Optometrics manufacture ruled polarisers by ruling precisely spaced grooves directly into high polished CaF2 or ZnSe substrates. The ruling process forms sharp, well defined peaks which are then coated with aluminum at an oblique angle, resulting in a series of closely spaced, highly conductive wires with a high extinction ratio and an inherently high damage threshold, allowing the use of the ruled polarisers with relatively high power lasers. Typical damage thresholds are 100 W/cm² CW and 2 J/cm² pulsed.
