Switchable waveguiding in two liquid-crystal-filled photonic crystal fibers.

Switchable waveguiding is investigated in two liquid-crystal-filled photonic crystal fibers with a solid core using the nematic liquid-crystal mixture E7 under planar and homeotropic anchoring conditions. Addressing experiments using ac voltages show polarization-dependent and -independent effects with response times down to a few ms. It is shown that the attenuation spectra of the two liquid-crystal-filled photonic crystal fibers can be changed dramatically by just varying the boundary conditions. Electromagnetic field simulations are presented, which are in good agreement with the experimental findings.

Infiltrated photonic crystal fiber: experiments and liquid crystal scattering model.

Experimental results obtained by means of a cut-back technique indicate low attenuations (< 1 dB x cm(-1)) for a solid core photonic crystal fiber filled with the nematic liquid crystal E7. These results observed in the visible wavelength range are compared with electromagnetic field simulations. The latter are carried out with a full vectorial finite element algorithm. Based on the modal properties under the condition of perpendicular anchoring of the liquid crystal molecules, the wavelength dependent attenuation is estimated using a power loss model considering the turbidity of the nematic liquid crystal. The results indicate that the scattering properties of this type of materials make them extremely interesting for fiber optical filters in the visible wavelength range and that filling materials with a relatively high turbidity are in general potentially useful as filling materials for solid core photonic crystal fibers.

Cryogenic 35GHz pulse ENDOR probehead accommodating large sample sizes: Performance and applications.

The construction and performance of a cryogenic 35GHz pulse electron nuclear double resonance (ENDOR) probehead for large samples is presented. The resonator is based on a rectangular TE(102) cavity in which the radio frequency (rf) B(2)-field is generated by a two turn saddle ENDOR coil crossing the resonator along the sample axis with minimal distance to the sample tube. An rf power efficiency factor is used to define the B(2)-field strength per square-root of the transmitted rf power over the frequency range 2-180MHz. The distributions of the microwave B(1)- and E(1)-field, and the rf B(2)-field are investigated by electromagnetic field calculations. All dielectrics, the sample tube, and coupling elements are included in the calculations. The application range of the probehead and the advantages of using large sample sizes are demonstrated and discussed on a number of paramagnetic samples containing transition metal ions.