Fused Silica is a high purity synthetic amorphous silicon dioxide. This noncrystalline, colorless, silica glass combines a very low thermal expansion coefficient with excellent optical qualities and exceptional transmittance over a wide spectral range, especially in the ultraviolet. It is resistant to scratching and thermal shock. Fused silica is available in a number of grades for different applications. One of the important applications is High Energy Laser Optics. No other optical material matches the purity of fused silica and therefore its ability to withstand and transmit high energy laser pulses with limited absorption or damage to the material. Fused Silica is used for windows, lenses, and prisms in the transmission range 0.16mm to 3mm. Its refractive index varies from 1.55 to 1.40 through the transmission range.