3. Antiresonant Fibers

Antiresonant hollow-core fibers (ARF) guide light in an air core surrounded by a thin ring of capillary tubes, relying on antiresonant reflection rather than a photonic bandgap or total internal reflection. This chapter computes their leaky modes and confinement loss using finite elements with a frequency-dependent PML, starting with the basic ARF geometry and then extending to nested antiresonant nodeless fibers (NANF), which add an inner ring of nested capillaries to further suppress loss.