Electrically controllable long-period liquid crystal fiber gratings

An electrically controllable fiber-optic filter for broad-band rejection ha s been demonstrated by periodically poling a liquid-crystalline core in a h ollow-core fiber by means of an external long-period-combed electrode. The periodically poled liquid-crystalline core in a period of 483 mu m couples the fundamental core mode to the leaky cladding modes. A maximum transmissi on loss dip of approximately 15-nm bandwidth and 6-dB band rejection has be en obtained for a nonpolarized light with a combed 250-V external voltage m odulation. The experimental result matches well with a numerical expectatio n, which has been analyzed by the discretized coupled-mode theory for an an isotropic perturbation.