Hybrid metal mesh-dielectric mirrors for optically pumped far infrared lasers

A hybrid metal metal-dielectrically coated mirror, highly reflecting in the near ir and partially transmitting in the far ir, for use in optically pumped molecular lasers, is described. Ge and CaF(2) were used for the dielectric films, along with Ni meshes deposited on Si substrates. The dielectric dispersion properties of the CaF(2) thin films were studied in the 2-15-microm range to provide design data. With a four layer dielectric coating and a metal mesh, the specular reflection of the mirror could be maintained greater than 90% over a 2-mum range in the near ir, and by choice of mesh, the transmittance in the 400-600-microm range varied from 0% to greater than 40%.