One of the key aspects to reduce disturbing influences on the laser signal in KAGRA is the setup of an efficient stray-light control. In particular, scattering as well as ghost beams produced by the various optical elements in the interferometer can make our efforts to discover gravitational waves vulnerable if we don't take enough care of it.
In this presentation, I review my work on stray-light control that I have done in the AOS. I especially focus on the measurement of scattering light and simulations on the mirrors and their recoil mass.