Toyohashi University of Technology researchers in collaboration with the Massachusetts Institute of Technology (MIT), have developed a new material capable of retaining high transmissivity after thermal treatment at 850°C and successfully applied the material to optical devices. The researchers alternately laminated film of this high-refractive-index material and film of a low-refractive-index material to form a dielectric mirror and then used the mirror for magneto-optical device production, which requires thermal treatment at high temperatures.