Rocking filter induced mechanically in a highly birefringent microstructured polymer fiber.

We present the possibility of mechanical inducement of a rocking filter in a birefringent microstructured polymer fiber, which resonantly couples polarization modes. A birefringence in the fiber used for rocking filter fabrication is induced by two large holes adjacent to the core. Because of the small pitch distance of the microstructured cladding, the phase and the group modal birefringence in this fiber are relatively high and equal, respectively, 1.2×10 and -2×10 at λ=800  nm, while the fiber loss is 5  dB/m at λ=850  nm. We demonstrate transmission characteristics of rocking filters mechanically induced in this fiber. A 22 dB deep first-order resonance located in the visible spectral range was observed, accompanied by a second-order resonance in the near-infrared. We also show that by changing the filter period and load applied to the fiber, one can tune the resonance position and depth.