The Nd:YAG crystal, also known as Neodymium-doped Yttrium Aluminum Garnet, is a highly efficient laser gain medium. This crystal is renowned for its exceptional laser gain even at moderate excitation levels and pump intensities, making it a popular choice in various laser applications. The Nd:YAG allows for high gain efficiency and low threshold pump power, making it a versatile and cost-effective solution for laser systems. One of the key attributes of the Nd:YAG crystal is its ability to be pumped by both diode and lamp sources, with flashlamp pumping being feasible due to its broadband pump absorption in the 800 nm region. This characteristic, combined with its four-level gain medium properties (except for the 946 nm transition), contributes to its widespread use. The most common emission wavelength for Nd:YAG lasers is 1064 nm, but other wavelengths such as 532 nm, 355 nm, and 266 nm can be achieved through frequency doubling, tripling, and quadrupling, respectively. Additionally, it offers emission lines at 946 nm, 1123 nm, 1319 nm, 1338 nm, 1415 nm, and 1444 nm. Nd:YAG crystals are typically produced in monocrystalline form using the Czochralski growth method, ensuring high quality and availability in large sizes. With typical neodymium doping concentrations around 1 at.%, these crystals can be tailored to specific needs by adjusting the doping levels. However, care must be taken to avoid excessive concentrations, which can lead to quenching of the upper-state lifetime and increased power density in high-power lasers. The robustness and versatility of Nd:YAG crystals make them ideal for a wide range of applications in fields such as medicine, defense, machinery, and scientific research.