Finite-difference time-domain methods

The finite-difference time-domain (FDTD) method is a widespread numerical tool for full-wave analysis of electromagnetic fields in complex media and for detailed geometries. Applications of the FDTD method cover a range of time and spatial scales, extending from subatomic to galactic lengths and from classical to quantum physics. Technology areas that benefit from the FDTD method include biomedicine - bioimaging, biophotonics, bioelectronics and biosensors; geophysics - remote sensing, communications, space weather hazards and geolocation; metamaterials - sub-wavelength focusing lenses, electromagnetic cloaks and continuously scanning leaky-wave antennas; optics - diffractive optical elements, photonic bandgap structures, photonic crystal waveguides and ring-resonator devices; plasmonics - plasmonic waveguides and antennas; and quantum applications - quantum devices and quantum radar. This Primer summarizes the main features of the FDTD method, along with key extensions that enable accurate solutions to be obtained for different research questions. Additionally, hardware considerations are discussed, plus examples of how to extract magnitude and phase data, Brillouin diagrams and scattering parameters from the output of an FDTD model. The Primer ends with a discussion of ongoing challenges and opportunities to further enhance the FDTD method for current and future applications. Time-domain solutions to Maxwell's equations can be computed using the finite-difference time-domain (FDTD) method. This Primer explores how FDTD can be used to study electromagnetic fields in complex media, including a summary of FDTD models, extensions, outputs and applications across the electromagnetic spectrum.