Paratellurite, also known as Tellurium Dioxide (TeO2), is a birefringent crystal material that is used in a variety of optical applications. It is a material that has high transmission in the infrared (IR) and ultraviolet (UV) regions, making it ideal for use in spectrometers and other optical systems. The birefringent properties of paratellurite allow it to split light into two orthogonal polarizations, which is useful in applications such as polarization splitting and analyzing. Additionally, the high index of refraction and low absorption loss of paratellurite make it an ideal choice for use in acousto-optic devices, where high-frequency sound waves are used to modulate light.