Ceramics

Isolator transmits the light only one direction and remove the reflected and returned light

It is used as a unit combined with optical fiber. TGG (Tb₃Ga₅O₁₂) has a higher Verdet constant than the existing Tb-doped glass and exhibits an excellent Faraday effect.
And it can be combined for high-power laser, since it has high thermal conductivity.
TAG (Tb₃Al₅O₁₂), which has higher performance than TGG, is also under development. [R&D page]

① Incident light is rotated 45 degrees by Faraday rotator
② The returned light is further rotated by 45 degrees, and removed by polarizer1.