·Broadband reflectors

·Not sensitive to polarization and incident angle

·Low damage threshold, can NOT be used on high power lasers

Metallic coatings make very broad bandwidth reflectors. Usually it is best to protect the coatings with a durable dielectric layer as they are very soft and susceptible to scratching. The efficiency of metallic reflectors flls off at shorter wavelengths but this may be enhanced by the application of a multi-layer dielectric thin film stack. The table shows the reflectance of each of the metals without any protection or enhancement.

Protected metallic coatings have a dielectric coating layer over the metallic layer to protect the coating from being oxidized in the air or from scratched.

For enhanced metallic coatings, a tack of dielectric layers are added on the metallic coating to increase reflectance for a particular wavelength range.

Coating code                                  Specifications                                            Average Reflectance(%)           

     ·PAL                                      ·Protected Aluminum Coating                                                     ·87.0                         

     ·EAL                                     ·Visible Enhanced Aluminum Coating                                        ·93.0                         

     ·PAG                                     ·Protected Silver Coating                                                             ·98.0                         

     ·EAG                                     ·Enhanced Silver Coating                                                            ·99.2                         

     ·PAU                                     ·Protected Gold Coating                                                               ·98.0

     ·EAG                                     ·Enhanced Gold Coating                                                              ·99.1