Selective coupling of fibre modes using surface-guided Bloch modes supported by dielectric multilayer stacks

The surface-guided Bloch modes guided by the interface between a multilayer dielectric stack and an external medium are highly dispersive. This makes attractive their use in mode-selective coupling of light into 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 refractive 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.