GYSGG (Gd0.63Y2.37Sc2Ga3O12) substrates are made of garnet materials that have a combination of Gd, Y, Sc, Ga, and O elements. These substrates are used in various optical applications, including laser and non-linear optics, due to their high thermal conductivity, low thermal expansion coefficient, and high damage threshold. Additionally, they have a broad transparency range, making them useful for a variety of wavelength ranges. They are often used as substrates for non-linear optical devices, optical amplifiers, and laser crystals, among others.