Quartz UV and far infrared optical performance is outstanding and easy to control, suitable for high-end optical components
Quartz has outstanding optical performance in the ultraviolet and far infrared bands and is suitable for high-end optical components. Fused silica is particularly advantageous in the ultraviolet (<300 nm) and far-infrared (800-3500 nm) or other bands that require high optical uniformity due to its high purity and homogeneity. Depending on the application, there are the best grades of fused silica material to choose from. For example, by selecting different raw material sources (quartz containing minerals or synthetic chemicals, such as Ar element) and manufacturing methods that produce different hydroxyl (OH) content, it can be used for ultraviolet transmission, infrared transmission, broadband transmission and Different levels of uniformity in three or three dimensions optimize each corresponding quartz grade. For even shorter wavelengths of light (Extreme Ultraviolet, EUV), a transmissive optical system is not suitable, so a reflective system (planar or curved mirror) may be used. Some of the optical instruments used in extreme situations, such as spacecraft lenses or transparent windows, also need to be able to resist high radiation or pressure differences under extreme conditions.
The optical properties of quartz mainly depend on the control of purity and hydroxyl content. Optical properties are largely dependent on the purity and hydroxyl content of the material. The water dissolved in quartz is called hydroxyl (-OH), which is the main impurity in quartz. The main factors affecting the hydroxyl content are raw materials, processes and processing methods. The vibration or rotation or excitation of metal impurities and hydroxyl molecules will cause light absorption in the material, resulting in reduced light transmission and material heating. As the hydroxyl content increases, the viscosity, density, and refractive index of quartz decrease, infrared absorption, and expansion coefficient increase. Quartz with a hydroxyl content of 100-200ppm can be removed by heating at more than 900 degrees.
The CVD method has outstanding performance in quartz far infrared, and the indirect synthesis method has excellent performance in ultraviolet and strong laser applications. At present, the CVD process is currently the most mature and commercial process. The diameter of the prepared quartz can reach more than 600 mm, the optical uniformity is better than 2 × 10-6, and the laser damage resistance threshold is very high. In aerospace, laser nuclear technology, The field of precision instruments and semiconductors has been widely used. The quartz produced by the PCVD process has excellent intrinsic quality, hydroxyl content ≤ 5 × 10-6, and spectral transmittance T190-4000 nm ≥ 80%, which meets the application requirements of high-end infrared optoelectronic devices and optical communications. However, due to high preparation costs, Get mass applications. The indirect synthesis method is a process technology developed in the past ten years. The quartz produced by this technology has a small light absorption coefficient, a hydroxyl content of ≤1 × 10-6, a spectral transmittance of T157-4000 nm≥80%, and is easy to mix. It is the first choice for preparing various high-end (doped) functional optical quartz. At present, the indirect synthesis method has been initially applied in the fields of vacuum deep ultraviolet, extreme ultraviolet and intense laser.