Optical crystals are transparent in different spectral regions, depending upon the crystal material. They include nonlinear, photorefractive crystals, and laser crystals’ acousto-optic and electro-optic combinations; X-ray analysis and scintillation crystals; and other types of crystals that are used in semiconductors.
Optical crystals are used mainly in laser applications. For example, non-linear devices are used as frequency converters and consist of a crystal made of lithium niobate, barium borate, lithium triborate, and potassium titanyl phosphate. Each has specific operating characteristics and should be selected based on the laser application. For example, a lithium niobate crystal may be used to as a frequency doubler in an optical parametric oscillator (OPO) device.
Optical crystals can be used in many different infrared (IR) laser applications. Examples include scintillation detectors and gas analyzers. These crystals are also widely used in military infrared optical devices. Crystal sapphire optical components are used in high power laser windows. Some optical crystals are clear or colorless. Acousto-optical crystals such as tellurium dioxide can be used in argon laser applications.