The reflective coating of D-shaped mirrors extends to near the flat edge of the mirror, enabling the separation of closely spaced optical beams. An example application is a folded geometry prism compressor used to shorten the duration of a positively chirped ultrashort laser pulse. As the image shows, the beam entering the prism assemblies passes slightly above the D-shaped mirror. The beam exiting the prism assemblies travels slightly below, and in the same vertical plane as the entering beam, but is then "picked off" by the D-shaped mirror and routed to an autocorrelator. A D-shaped mirror improves the efficiency of such a prism compressor because it enables the entering and exiting beams to be placed much closer to each other than a round mirror would allow. For more information, see our Prism Compressor for Ultrashort Laser Pulses application note, and our Beam Pickoff With D-shaped Mirrors Application Set-up

Our BD.1 visible broadband dielectric coating reflects all visible wavelengths from 488 to 694 nm with greater than 99% efficiency for s-polarization, and 98% for p-polarization, at 0 - 45° angle of incidence. High reflectivity is also extended to greater than 98% for 441.6 nm.

As the reflective coating extends to near the flat edge of the mirror for pickoff applications, the flat edge is cut very sharp with no bevel. Thus, special care should be taken when handling to avoid injury. Furthermore, other contact with the flat edge should be avoided as much as possible to prevent the mirror from becoming chipped, including mounting in standard mirror mounts. Newport recommends HM-1 or M1-1D Edge Grip mirror mounts for all d-shaped mirrors.