SELECTIVE COUPLING OF FIBER MODES WITH USE OF SURFACE-GUIDED BLOCH MODES SUPPORTED BY DIELECTRIC MULTILAYER STACKS

The surface-guided Bloch modes guided by the inter-face between a mult ilayer dielectric stack and an external medium are highly dispersive. This makes attractive their use in mode-selective coupling of light in to and out of side-polished multimode fibers. The particular case of a dual-mode fiber is modeled. Mode selection by means of surface-guided Bloch modes is found to offer advantages in comparison with selection by means of a single-mode waveguiding film of the same average refrac tive index as the stack. Good modal selectivity is achievable together with high tunability, i.e., high sensitivity to the refractive index of the intervening layer between stack and side-polished fiber. (C) 19 95 Optical Society of America