Also known as dispersive prism, a beam of white light is incident, which can separate and scatter light of different wavelengths. It is often used for dispersion compensation in optical splitter or femtosecond laser resonator. Compared with 45 right-angle prism, it has better wavelength dispersion characteristics, higher efficiency and easier to observe its spectrum. The three surfaces of the regular triangular cylindrical surface are ground and polished, which can be selected at will.