Magnesium fluoride is probably the most widely used thin film material for optical coatings. Its performance is not outstanding but represents a significant improvement over an uncoated surface. Because its index is too high to provide a good impedance match at the air-glass interface. Partial reflectors provide a known reflectance at the wavelength of interest. They have an anti-reflection V-coat applied to the rear surface. Reflectance and wavelength may be chosen by the user. The range and tolerance of reflectances offered and the common laser wavelengths are listed in the table. Partial reflectors may be used as laser output couplers. Remember that the reflectivity chosen determines the gain of the laser; high gain requires low reflectivity. An appropriate output coupler should be selected to maximize the output power/energy ratio. Note that Lambda high quality visible laser cavity coatings are designed for low scattering. These partial reflectors may also be used as extra-cavity beam dividers. Please specify angle of incidence and polarization if the partial reflectors are to be used at other than normal incidence.

Partially reflective Coating @ 532nm with 90% reflectance