# Crystals

Crystals are highly ordered, periodic structures that offer a range of unique optical properties unattainable with amorphous materials like glass. Comprising atoms, ions, or molecules arranged in a repeating lattice structure, crystals can be engineered or selected to exhibit specific characteristics such as high refractive indices, low dispersion, and even nonlinear optical behavior. Commonly used optical crystals include quartz, sapphire, and various synthetic materials like potassium titanyl phosphate (KTP) and lithium niobate (LiNbO3). These materials are often used in applications that require high levels of precision and performance, such as in laser systems, optoelectronic devices, and frequency converters. Crystals can also demonstrate phenomena like birefringence, where the refractive index varies depending on the polarization and direction of light, making them invaluable in specialized optical components like waveplates and polarizers. Advanced crystal structures like photonic and plasmonic crystals can manipulate light at the nanoscale, offering avenues for research and application in areas like integrated optics and quantum computing. It's important to note that the optical properties of crystals, such as their refractive index and absorption coefficients, can be highly anisotropic and dependent on the crystal orientation. Therefore, specific data must be consulted for precise applications. Overall, crystals offer a broad palette of options for manipulating light, making them integral to both classical and cutting-edge optical technologies.

## External links

- Crystal - Wikipedia