High-refractive-index material retains high transmissivity after annealing at 850 degrees C
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.
Recent research has shown that combining well-known, superior materials can yield new materials that have a greatly enhanced performance compared to conventional materials. However, combining different materials often proves to be a challenge; a material with good properties when used alone can cause new problems when combined with another material. Heat-related problems are among the easiest of these problems to understand. For example, when a material that requires thermal treatment at a certain temperature is combined with another material that degrades at that temperature, the resulting product's performance is degraded, making such a combination pointless.
In this study, the research group of Toyohashi University of Technology in collaboration with Massachusetts Institute of Technology (MIT) alternately laminated a high-refractive-index material and a low-refractive-index material to form a dielectric mirror and combined it with transparent magnetic garnet. The magnetic garnet requires thermal treatment at about 750°C during formation, and therefore the dielectric mirror needs to withstand this temperature. It is well known that tantalum oxide3, which is widely used as a high-refractive-index material in dielectric mirrors, crystallizes and loses much of its transmissivity at about 700°C.
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