Optical Properties of Quartz Glass

Optical Properties of Quartz Glass
One of the important differences between quartz glass and ordinary glass is its good transmittance in the entire spectrum, especially the transmittance in the ultraviolet and deep ultraviolet spectrum that ordinary optical glass does not have. But this kind of good permeability depends to a large extent on the chemical purity of the quartz glass. Even 0.001% of impurities will cause the optical permeability to deteriorate significantly, however, this impurity has little effect on its mechanical properties, thermal properties and electrical properties. The optical transmission properties of quartz glass manufactured with different raw materials and different processes are different as well. There are different cut-off wavelengths in the ultraviolet band, and the hydroxyl group will have a deep absorption peak in the infrared band. Therefore, some are suitable for working in the infrared band, and some are suitable for working in the ultraviolet band. For example, quartz glass used for integrated circuit lithography needs to be able to transmit deep ultraviolet light below 200 nm.
The following figure shows the transmittance curve of the main transparent quartz glass varieties.

The refractive index of quartz glass varies with the wavelength of light and is related to temperature. There are also differences between crystal raw materials and glass made by synthetic methods, as shown in the table below. Important optical components pay much more attention to the uniformity of the overall refractive index of the component, which can be as high as 1X10-6.
                                                                 Refractive Index of Quartz Glass

Wavelength/nm	Quartz glass melted by powders	Quartz glass melted by synthesis method
202.54	1.54729	1.54717
253.70	1.50590	1.50555
361.17	1.47520	1.47513
589.60	1.45861	1.45841

Mechanical stress inside the quartz glass can also cause birefringence. Annealing to eliminate stress can effectively improve birefringence. After the precision-machined workpiece is treated with hydrofluoric acid, the stress at the corners can be eliminated.
Quartz glass will cause fluorescence under certain wavelengths of light.