Multipole method for efficient microstructured optical fiber calculations

Summary form only given. Microstructured optical fibers (MOFs) are among the most exciting recent developments in fiber optics. Typically these consist of a glass core surrounded by circular airholes running parallel to the fiber. MOFs have properties that can differ substantially from conventional step-index fibers, such as unusual dispersion characteristics, low or high effective nonlinearities, and many others. The number of air holes can be as small as six, in which case the energy confinement is imperfect and the modes are leaky. More generally, all modes of MOFs with a finite number of holes and no other confinement mechanism, are leaky. We report a multipole expansion method for full-vector modal calculations of MOFs with circular holes. Since this is the natural type of expansion for structures with circular inclusions, it is very efficient.