Modeling endface output patterns of optical micro/nanofibers

Endface output patterns of micro/nanofibers (MNFs) are simulated using a Three-Dimension Finite-Difference Time-Domain (3D-FDTD) method. The intensity distribution and beam widths of near-or far-field output patterns of freestanding silica and tellurite MNFs with flat, angled, spherical and tapered endfaces in air and/or water are obtained. It shows that, for a subwavelength-diameter MNF, highly confined output beam can be obtained in the near field, and the beam width can be tuned by the ratio of fiber diameter and light wavelength with a minimum width smaller than the wavelength. Meanwhile, MNFs with shaped endfaces behave differently from standard fibers in reflection, redirection and focus of light beam at the endfaces. These results may offer valuable references for practical evaluation and application of terminated MNFs with wavelength-or subwavelength-scale endfaces. (c) 2008 Optical Society of America.