Explore the frontiers of photonics and master optical nonlinearities with this definitive guide to chalcogenide glasses. Discover their critical role in 21st-century technologies like advanced frequency conversion and high-speed optical switching. This comprehensive review details material properties, characterization techniques, and the fabrication of passive and active devices. An indispensable resource for graduate students, researchers, engineers, and material scientists in physics, chemistry, and electrical engineering across India, looking to innovate in optical materials and photonics applications.