Neodymium Doped Yttrium Aluminum Garnet (Nd:YAG)

Neodymium-doped yttrium aluminum garnet (Nd:YAG) has been widely used as a solid state laser host material. It is a stable compound, mechanically strong but brittle, optically isotropic, and chemically stable in most acids including nitric acid (HNO3) and hydrofluoric acid (HF). Its good fluorescent lifetime, thermal conductivity and physical strengths make it suitable for high power lamp pumped laser. Nd:YAG can be grown by CZ method with very low strain. The YAG host is transparent from below 300 nm to beyond 4 microns, and accepts trivalent laser activator ions (Y³⁺).

Extinction Ratio:  

Strain and other imperfections in the Nd:YAG induce local birefringence and inhomogeneity, cause wavefront distortion, and change polarization states. Extinction ratio is a simple method to quantify the residual birefringence and inhomogeneity in a laser rod. The extinction ratio is measured by using a HeNe laser source with a laser rod sandwiched between two polarizers. The extinction ratio is defined as 10*log (T1/T2), where T1 is the maximum transmitted beam intensity with the polarizers uncrossed, and T2 is the minimum beam intensity with the polarizers crossed.