Optical crystal's introduction

Optical Crystal is a kind of Crystal material used for Optical medium materials. It is widely used in making window pieces, lenses and prisms in various fields of ULTRAVIOLET and infrared application. According to the crystal structure is divided into single crystal and polycrystal. Single crystal materials have high crystal integrity and light transmittance, as well as low input loss, so common optical crystals are dominated by single crystal.  

Optical single crystal materials:  

Halide single crystal:

Halide single crystal is divided into fluoride single crystal, bromine, chlorine, iodine compound single crystal, thallium halide single crystal.  Fluoride single crystal has high transmittance, low refractive index and low light reflection coefficient in ultraviolet, visible and infrared spectral regions. Disadvantages are large expansion coefficient, small thermal conductivity, poor impact resistance. The single crystal of bromine, chlorine and iodine can pass through a very wide infrared band and its melting point is low, so it is easy to make large single crystal. Disadvantages are easy deliquescence, low hardness, poor mechanical properties. Thallium halide single crystal also has a wide infrared spectral transmission band, slightly soluble in water, is a detector window and lens material used at lower temperatures; The disadvantage is that there is cold rheology, easy to be corroded by heat, toxic.  

Oxide single crystal:

Typical single crystals include sapphire (Al2O3), magnesium oxide (MgO), rutile (TiO2), crystal (SiO2), etc. Compared with halide single crystal, it has high melting point, good chemical stability and good transmittance in visible and near infrared bands.  

Semiconductor single crystal:

Semiconductor single crystal has single crystal (such as germanium single crystal, silicon single crystal), II-VI group semiconductor single crystal, III-V group semiconductor single crystal and diamond. Diamond is the crystal with the longest spectral transmission band, which can be extended to the far infrared region, and has high melting point, high hardness, excellent physical properties and chemical stability. Semiconductor single crystal can be used as infrared window material, infrared filter and other optical elements.  

Optical polycrystalline materials:  

Optical polycrystalline materials are mainly hot-pressed optical polycrystalline materials, which are obtained by hot-pressed sintering process. There are oxide hot-pressed polycrystalline, fluoride hot-pressed polycrystalline and semiconductor hot-pressed polycrystalline. In addition to excellent light transmittance, hot-pressed optical polycrystals also have excellent mechanical and physical properties such as high strength, high temperature resistance, corrosion resistance and impact resistance, which can be used as optical elements and window materials for various special needs.  

Characteristics of optical crystals:  

Birefringence: Crystal birefringence is caused by the anisotropy of polarizability, which is determined by the anisotropy of crystal structure.  The degree of birefringence of crystal depends on different crystal families.  

Optical rotation: when a plane polarized wave propagates along the optical axis, its plane of polarization rotates, which is called optical rotation.  Its internal structure has an unsymmetrical spiral structure.  

Absorption and polychromism: the absorption of light by crystals is anisotropic.  When the incident light is in the same direction as the vibration with a larger refractive index, the absorption is stronger. Except for equiaxed crystals, the same crystal presents different colors in different directions.  

Solution: the ability of a crystal to split into a smooth plane in a certain direction under the action of an external directional mechanical force.