High-reflectivity lead-salt-based Bragg mirrors for the mid-infrared range

High-quality lead-salt-based Bragg mirror stacks were fabricated on BaF/sub 2/(111) substrates by molecular beam epitaxy. The mirrors consisted of Pb/sub 1-x/Eu/sub x/Te quarter-wavelength layer pairs with 1% and 6% Eu content and were designed for use in mid-infrared (MIR) vertical emitting devices with a PbTe active zone. From theoretical simulations, we obtained the internal reflectivity with incidence from an active resonator medium and the reflectivity spectra of Bragg/metal mirror combinations. For a 32-layer pair mirror, we measured a record stopband reflectivity for the MIR of over 99% at 5.7 /spl mu/m, in excellent agreement with our calculations.