Effect of bending on surface plasmon resonance spectrum in microstructured optical fibers.

We analyzed the effect of fiber bending on spectral position and strength of the surface plasmon resonance arising due to the interaction of the fundamental mode guided in the core of the microstructured fiber with a metal layer. Fully vectorial simulations were performed using the finite element method with perfectly matched layers boundary conditions. To conduct the simulations, we adopted the concept of an equivalent bent fiber developed recently on the ground of transformation optics formalism. In this approach, the bent fiber with a metal layer is replaced by an equivalent fiber with appropriate spatial distributions of electric permittivity and magnetic permeability tensors. The obtained results explain the mechanisms responsible for the change in the SPR spectrum induced by bending and by the geometry of the microstructured fiber. By modifying the holes layout in the microstructured cladding, we designed the fiber, in which the depth of the surface plasmon resonance is in a high degree tunable by bending.