Silicon Has Good transmission at 1-7um. It is widely used for 3-5um infrared windows and lens. Changchun Yutai Optics Co.Ltd is good at producing big size Silicon window and Lens. Thermal Infrared Lens are used in a variety of infrared applications operating in the 8 - 12μm wavelength range, including NIR imaging or IR spectroscopy. Silicon’s low density (2.329 g/cm3) is ideal for use in weight-sensitive applications. Silicon features a Knoop hardness of 1150, making Silicon Optical Components harder, less brittle alternatives to comparable Germanium Optical Components.