The article discusses NIST’s research on calculating the optical properties of materials using the Bethe-Salpeter Equation (BSE) method. The main objectives are to reliably predict bulk optical properties like refractive index, absorption, and reflectance across the electromagnetic spectrum. This helps understand material properties and improve predictions for complex systems like photonic crystals and optical fibers.
NIST maintains two BSE calculation methods: one for valence excitations (near-infrared to near-ultraviolet) and one for core excitations (x-ray). They also have an atomic structure calculation program that interfaces with the BSE code for core excitations.
Current limitations include the extensive effort required to calculate dielectric screening effects and electron/hole lifetime-damping effects, which restricts the scope of systems that can be easily studied with BSE calculations. NIST is seeking to identify key aspects of dielectric response and develop model dielectric functions and one-electron self-energies to advance BSE calculations.
The article also mentions recent work providing theoretical guidance for quantum information in solid-state systems, such as calculating the feasibility of a heralded single-photon source in rubidium-diffused potassium titanyl phosphate (RTP/KTP) crystals operating in the 1550 nm telecommunications band without the need for poling.
The valence NBSE program has been equipped with a user-friendly interface, and a utility has been prepared to translate output from a popular density-functional band-structure program into input suitable for the valence NBSE.
Source: https://www.nist.gov/programs-projects/theory-optical-properties-materials
Keywords: Excitonic, Dielectric, Electromagnetic, Photonic, Spectra
