Polyetherimide (PEI, (C37H24O6N2)n) is a high-performance amorphous thermoplastic polymer distinguished by its amber-to-transparent appearance. Notable for its combined characteristics of high strength, dimensional stability, and heat resistance, PEI is also inherently flame retardant and exhibits good electrical properties. Owing to its unique combination of transparency and its ability to withstand elevated temperatures, PEI finds applications in a variety of industries. In the realm of optics, PEI's inherent transparency across a substantial portion of the visible spectrum and into the ultraviolet range positions it as a material of choice for certain optical components. Its exceptional heat and flame resistance, coupled with its electrical insulation capabilities, also make PEI a preferred material in the electronics industry for components like circuit boards, connectors, and cable insulation. The polymer's intrinsic robustness and chemical resistance extend its usability to the medical and automotive sectors as well, where high-performance materials are a necessity. The refractive properties of PEI stem from its molecular structure, with the polymer's repeating units contributing to its distinct optical attributes.