Optical filter is made of plastic or glass and special dye. Red filter can only let red light pass through, and so on. The transmissivity of glass is almost the same as that of air. All colored light can pass through it, so it is transparent. However, after dyeing with dye, the molecular structure and refractive index will change, and the passing of some colored light will change. For example, when a beam of white light passes through a blue filter, it emits a beam of blue light, while the green light and red light are very few, and most of them are absorbed by the filter.
Laser glass is a kind of solid laser material based on glass. It is widely used in all kinds of solid-state lasers, and has become the main laser material for high-power and high-energy lasers. Compared with laser crystal, laser glass has the following advantages
(1) It is easy to prepare. High transparency and optical uniformity glass can be obtained by using and improving the preparation technology of optical glass. It is easier to prepare large-size working object with low cost. Large volume and high density of active particles are important advantages for high-power and high-energy lasers.
(2) The matrix glass is easy to change. The composition and properties of the matrix glass vary widely, and the type and quantity of activators are not limited, so it is easy to develop into a series of laser glass with various characteristics.
(3) Easy to form and process. Using the technology of optical glass hot forming and cold processing, laser glass is easy to be directly formed into various shapes, such as rod, sheet, wire, etc., and to be densified into high-precision optical surface to meet the needs of the development of various device structures.
(4) Based on the characteristics of glass structure, that is, short-range order and long-range disorder, the structural defects in glass have little influence on the glass breaking properties and are easy to eliminate, so it is easy to obtain isotropic and uniform working materials with large volume. Neodymium glass is the main laser glass because it can produce laser at room temperature, has low temperature quenching effect and high quantum efficiency of optical pumping absorption and luminescence.